Redesign a Fiero suspension for better geometry (Solidworks, ProEngineer, etc)
Topic started by: Austrian Import, Date: 06-30-2011 06:13 PM
Original thread: http://www.fiero.nl/forum/Forum2/HTML/117227.html


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #1, 06-30-2011 06:13 PM
      We all know that the '88 Fiero suspension is (arguably) better. But it's still 20 years old.

I always wondered if with modern CAD/CAM software it would be possible to design a more modern
A ) Double wishbone front + Double wishbone rear
B ) Double wishbone front + fancy multi-link rear
C ) another option I hadn't considered.

It would be great if it were to (almost) bolt in to the vehicle. Maybe use factory rear cradle attachment points and replace the rear cradle. The front end may be replaced as well, while utilizing the attachment points.

The goal is to apply what engineers have learned about suspension design in the last 30 years since the Fiero was built.

Let's put considerations such as: feasibility of actually making it a real life product, costs/reward, starting over with a tube-frame chassis, etc. on the back burner to let creativity flow.

Reasons I thought it would be a great idea to do this:
1) It is a great way to learn/share ideas about modern suspension theory
2) Learn suspension design applied to a specific project (with applied constraints), rather than just complete theory, or a scratch build vehicle.
2) hopefully get a good debate going (please without name calling, etc. let's keep this civil)
3) See how open source/collaborative thinking would work out in the Fiero world
4) provide an avenue to share technical information/content for people with similar interests.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #2, 06-30-2011 06:28 PM
      A couple great ideas from existing threads to get the ball rolling:

 
quote
Originally posted by 88lambo: in http://www.fiero.nl/forum/F...2/HTML/107913-5.html

Update...

Picking away at the cradle and the Fiero chassis, I got the fire wall stripped of all the brackets getting ready to cut the rear section off and start on building the tube frame from the firewall back.
I put the cradle into the chassis to see how it lined up, if you look at the photo from the back straight on you can see the center vertical tube are the same distance from the Fiero frame (which will be gone soon)
Tranny coming off engine this weekend then off to be rebuilt...

I guess since I will be cutting most of the rear section away I couldn't really call this a "Stock" engine compartment any more...so if you wanted to put this into a Stock Fiero I would retain the rear frame section (trunk still has to go) make the cradle suspension mounting points to use the fiero suspension components. You could use my lower suspension arms in conjunction with the Fiero rear shocks (or a coilover kit) and the stock shock tower...I still believe if you wanted to you could stuff this setup into a Fiero...which would be cool...Maybe my next project, a Fiero with the BMW V12 twin turbo!!!!













 
quote
Originally posted by ccfiero350: in http://www.fiero.nl/forum/F...3/HTML/000094-9.html


Here are some side by side images.

The new front end is about 30lbs heavier then the original one.


Most of it is in the new brakes.


They are just frigging big.


I can't wait to see how HHP's adjustable bars work out on the track.


The front sway bar on the old front end is an Addco bar that's 1.25" thick.


I have to admit with the mods done to the front sheet metal for the flip front end it made working on it much easier.


I balanced it on the floor jack and just lifted up in place in one piece.


1st trick is get the rear tab under the chassis mount pad. 2nd trick is get the alignment pin on the drivers side in it's hole.


Once you get the pin in, the rest of the bolts pull it pretty much into alignment.

[This message has been edited by Austrian Import (edited 06-30-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #3, 06-30-2011 06:31 PM
     
 
quote
Originally posted by ccfiero350:

It been a while since I have posted here but work has been on going. I have been working with coppertop_01 designing some new suspension pieces.


There rear knuckle for an 88 is a unique piece, and limits the use of larger unitized bearing hubs. So I designed a new one that uses a Saturn Vue hubs and axle.


To fit my IMSA wide body, I need a least a 10 1/2" wheel, and cheap wide wheels come on mustangs. I also incorporated C4 disc with calipers mit parking brakes.


So my special thanks to bloozeberry for his subframe prints, I made a full math model of the 88 rear suspension.


This version features some changes in geometry to help with roll center, camber gain and anti squat with the 2" lowering.


I can do motion analysis with the software with animations, make changes and run it again. Really fun stuff.


I've got some mods to the sub frame that will re-locate the links a tad to fine tune the roll center.


 
quote
Originally posted by ccfiero350:

I did some motion analysis on the new knuckle and made some quickie low rez animations.




Austrian Import (maximilian_ledworowski@csumb.edu) MSG #4, 06-30-2011 06:34 PM
      One approach would be to add SLA's to the rear of the Fiero.

 
quote
Originally posted by Austrian Import:

Agent 47







Austrian Import (maximilian_ledworowski@csumb.edu) MSG #5, 06-30-2011 06:41 PM
     
 
quote
Originally posted by Austrian Import:

The other idea I had was to mimic (or buy at $300-$600) a Porsche Boxster rear suspension:








Austrian Import (maximilian_ledworowski@csumb.edu) MSG #6, 06-30-2011 06:53 PM
      Coppertop's scratch built '88 engine cradle shows part of what I envision in this thread:









http://coppertopautosports....dle-fabrication.html
http://coppertopautosports....-fabrication_06.html
http://coppertopautosports....-fabrication_10.html



sspeedstreet (sspeedstreet@verizon.net) MSG #7, 07-01-2011 01:20 PM
      I've been thinking of the same things. I was looking at the Mustang SLA setup as well. The Fiero design wouldn't need the ball joints, but would need the strut pickup on the upright moved to clear the axle. To the side or my choice:



This animation shows a rocker type strut instead of the stock Fiero position, but you get the idea:


(Credit to dave@team321.com)

[This message has been edited by sspeedstreet (edited 07-01-2011).]

Bloozberry MSG #8, 07-01-2011 02:07 PM
     
 
quote
Originally posted by sspeedstreet:

The Fiero design wouldn't need the ball joints...


Enlighten me please. I'm not sure what you mean by this, but if you're suggesting that the upper control arm could be solid mounted to the knuckle, you wouldn't be able to control dynamic camber changes. On the other hand, if you meant that you could have a simple fulcrum at the top of the knuckle (like the lower lateral links on an '88) then you wouldn't be able to effect dynamic toe changes:

1. without soft fulcrum bushings, which would allow undesirable deflection of the arms in all axis, or;
2. without binding the upper and lower fulcrum bushings if using hard bushings, nor would it be very easy to adjust static toe.

The most versatile way to connect the knuckle to the control arms would be with ball joints, unless I'm over-looking something. If you're going to redesign the entire rear end, then it wouldn't make much sense to limit adjustablility unnecessarily.


sspeedstreet (sspeedstreet@verizon.net) MSG #9, 07-01-2011 04:35 PM
     
 
quote
Originally posted by Bloozberry:


Enlighten me please. I'm not sure what you mean by this, but if you're suggesting that the upper control arm could be solid mounted to the knuckle, you wouldn't be able to control dynamic camber changes. On the other hand, if you meant that you could have a simple fulcrum at the top of the knuckle (like the lower lateral links on an '88) then you wouldn't be able to effect dynamic toe changes:

1. without soft fulcrum bushings, which would allow undesirable deflection of the arms in all axis, or;
2. without binding the upper and lower fulcrum bushings if using hard bushings, nor would it be very easy to adjust static toe.

The most versatile way to connect the knuckle to the control arms would be with ball joints, unless I'm over-looking something. If you're going to redesign the entire rear end, then it wouldn't make much sense to limit adjustablility unnecessarily.


Obviously the lower ball joint is unnecessary on the 1988 design. The upper could be a spherical bearing. My point was there is no need to use the complexity of ball joints as there is no steering involved.


ccfiero350 (chuckcamp@gmail.com) MSG #10, 07-01-2011 05:29 PM
      Just my 2 cents worth, a spherical bearing, rod end, heim joint, what have you, technically has the same freedom of axis movement as a ball joint, but have to limit their off axis movement to keep the bearing in the cup.

A real good reason to keep with ball joints is that they are easer to seal up and kept lubed. But their not as sexy as heim joint



Bloozberry MSG #11, 07-01-2011 05:52 PM
     
 
quote
Originally posted by sspeedstreet:

The upper could be a spherical bearing. My point was there is no need to use the complexity of ball joints as there is no steering involved.


Two counter points:

1. Good rear suspension systems are designed to "steer" using the change in the geometry of the control arms as they rise or fall in jounce and rebound to effect it; and

2. As ccfiero stated, a spherical bearing (heim joint, etc) is just another form of a ball joint.


sspeedstreet (sspeedstreet@verizon.net) MSG #12, 07-01-2011 07:36 PM
     
 
quote
Originally posted by Bloozberry:


Two counter points:

1. Good rear suspension systems are designed to "steer" using the change in the geometry of the control arms as they rise or fall in jounce and rebound to effect it; and

2. As ccfiero stated, a spherical bearing (heim joint, etc) is just another form of a ball joint.


Minutia. This is not a rear steer application; toe changes due to suspension movement wouldn't be more than a couple of degrees. You need a ball joint for that?

Really, a ball joint is a type of spherical bearing? A Ferrari and a Prius are both automobiles, but their benefits are not interchangeable. I proposed eliminating the upper ball joint shown in the Mustang front SLR pictured above to free up that point as a strut mount.

Now, do you have anything constructive to add to the discussion or do you wish to continue with the critique?


ccfiero350 (chuckcamp@gmail.com) MSG #13, 07-01-2011 08:35 PM
      Minutia! What do you think suspension design is all about? We change our rear toe settings by 0.1 degrees and see measurable track time differences..

It IS about rear steering because it's built in the 88s. Why do you think the front horizontal link is shorter then the rear?



Will (william.lucke@gmail.com) MSG #14, 07-01-2011 08:50 PM
     
 
quote
Originally posted by Bloozberry:
1. Good rear suspension systems are designed to "steer" using the change in the geometry of the control arms as they rise or fall in jounce and rebound to effect it; and


I don't think I'd go that far...
That's like saying that you always want the front bar bigger than the rear... The real answer is "that depends on everything else".


Will (william.lucke@gmail.com) MSG #15, 07-01-2011 08:55 PM
     
 
quote
Originally posted by ccfiero350:

It IS about rear steering because it's built in the 88s. Why do you think the front horizontal link is shorter then the rear?



Umm... so what? Was that done for handling or packaging? How does that change the toe in bump? Droop? How does that change the toe in different conditions of bushing loading? If you're replacing the bushings with hard pivots, do you think the suspension still works the same way?
(Hint: I already know the answers; you don't need to lecture me...)
How does the '88 setup compare to equal length lateral/toe links, with the inner pivot of the rear link higher than the inner pivot of the front link?

FYI for everyone: The "oversteer moment" of a car is dependent on something like the FOURTH power of the rear toe angle. This means that tiny changes in rear toe have large effects in vehicle stability and "path accuracy".

In other words, your super trick geometry may produce a 0.1% effect, but that effect can easily be lost in the noise created by that last bushing you haven't replaced yet... or even if some component (like the cradle side rail, maybe?) isn't as stiff as you think it is.

Suspension design is more about not making gross mistakes than it is about getting everything excruciatingly perfect.

[This message has been edited by Will (edited 07-01-2011).]

Bloozberry MSG #16, 07-01-2011 09:51 PM
     
 
quote
Originally posted by sspeedstreet:

Minutia. This is not a rear steer application; toe changes due to suspension movement wouldn't be more than a couple of degrees. You need a ball joint for that?


I've already answered this question. It depends on how you plan to attach the strut and upper control arm to the knuckle.

 
quote
Originally posted by sspeedstreet:

Really, a ball joint is a type of spherical bearing?


Yes. Really. Ball = Spherical, Joint = Bearing in this case.

 
quote
Originally posted by sspeedstreet:

A Ferrari and a Prius are both automobiles, but their benefits are not interchangeable.


What does this mean?

 
quote
Originally posted by sspeedstreet:

I proposed eliminating the upper ball joint shown in the Mustang front SLR pictured above to free up that point as a strut mount.


Round and round we go. Again, exactly how would you attach the bottom of the strut to the knuckle, and to what and how would you attach the upper control arm?

 
quote
Originally posted by sspeedstreet:

Now, do you have anything constructive to add to the discussion or do you wish to continue with the critique?


Where'd that come from? I'm trying to understand what your proposal is.

 
quote
Originally posted by Will:

Suspension design is more about not making gross mistakes than it is about getting everything excruciatingly perfect.


 
quote
Originally posted by Will:

The "oversteer moment" of a car is dependent on something like the FOURTH power of the rear toe angle. This means that tiny changes in rear toe have large effects in vehicle stability and "path accuracy".


So which is it? Lecture us.


gusshotrod (gushotrod@aol.com) MSG #17, 07-02-2011 03:41 AM
      Rear roll steer is rear bump steer if it is designed into the suspension linkages. For roll steer to be independent from bump steer, it should be designed into the compliance of the linkage mounts, so that it is turned on by lateral loads, not vertical loads.

Will (william.lucke@gmail.com) MSG #18, 07-02-2011 07:55 AM
     
 
quote
Originally posted by Bloozberry:

So which is it? Lecture us.


Gross mistake = keeping the same component relationships in the rear of a Fiero as in the front of a Citation.

Tiny unintended toe changes can be greatly reduced with hard pivots.

 
quote
Originally posted by gusshotrod:

Rear roll steer is rear bump steer if it is designed into the suspension linkages. For roll steer to be independent from bump steer, it should be designed into the compliance of the linkage mounts, so that it is turned on by lateral loads, not vertical loads.


Do race cars never want roll steer?


gusshotrod (gushotrod@aol.com) MSG #19, 07-02-2011 12:32 PM
      Like you said Will, it depends on everything else. Active rear steer (which would be very useful) is not allowed in any form of racing that I am aware of. Passive rear steer is not used in drag racing. In circle track it is used, but mostly to make up for lack of available tire stagger. In road racing or on the street it is useless in high horsepower cars. For lower HP cars it can be useful IF you can divorce the bump steer from the roll steer AND if the rear tires end up with more slip angle than the front suspension. The rear suspension has no need to be better than the front, as you will never be able to use the improvement. I doubt if anybody drives on the street close enough to the limit to make rear steer worthwhile. It would be much more useful to limit toe change as much as possible to improve stability.

Bloozberry MSG #20, 07-02-2011 12:50 PM
     
 
quote
Originally posted by gusshotrod:

For lower HP cars it can be useful IF you can divorce the bump steer from the roll steer AND if the rear tires end up with more slip angle than the front suspension. It would be much more useful to limit toe change as much as possible to improve stability.


I'm not saying this isn't so, but I am curious to know what you think the rationale was behind the GM engineers decision to have unequal length lateral links on the '88 rear when they started with a wholesale redesign of the cradle and suspension. It certainly wasn't because of packaging constraints. The only purpose I can see for it is to provide dynamic toe change, which seems to be a contrary point of view from what you've stated as the ideal.


gusshotrod (gushotrod@aol.com) MSG #21, 07-02-2011 01:24 PM
      One reason could be to limit toe out under acceleration, another could be that it would be safer for the average driver to design in some roll understeer.

sspeedstreet (sspeedstreet@verizon.net) MSG #22, 07-02-2011 03:35 PM
      This is why this forum wears me down sometimes. An idea is proposed for discussion and immediately people jump in with minutiae. As in details that are of no consequence at the point of discussing the feasibility of an idea. Is an SLA design possible for the rear of a Fiero? Is it worth the effort? Is there sufficient strength in the stock wheel-well to support the UCA mounting points or will it need a subframe designed? Is there room enough for links of sufficient length on the passenger side even if you built a subframe? I don't know about your cars, but mine has an alternator pulley up against the inside of the wheel-well.

SLA systems exist. Bearings, bushings, ball joints, anti-squat, roll-steer . . . these are all things that can be designed in or out any way you want. They are not relevant (to me, anyway) at this point.

As for my comment "Really, a ball joint is a type of spherical bearing? A Ferrari and a Prius are both automobiles, but their benefits are not interchangeable.". There needs to be a sarcasm font. Of course I know a ball joint is a type of spherical bearing, but they each have there own application.

I guess I just hate to be lectured to.


gusshotrod (gushotrod@aol.com) MSG #23, 07-02-2011 03:50 PM
      Can it be done? Yes. Worth the effort? That is entirely up to you. This is a hobby. Enjoy yourself.

kennn (kbrooksarchitect@cox.net) MSG #24, 07-02-2011 05:29 PM
      Interesting discussion, and a nice front suspension mod by ccfiero. I have wondered if one could utilize the rear strut knuckle and lower suspension as is. Then, to the top of the knuckle, add a metal piece that would clasp the top of the knuckle, bolting through it in two places, that would have provision to receive a ball joint from an upper suspension arm with appropriate anti-dive angle. The principal advantage would be more ideal camber change geometry than the strut type geometry.

Ken



Bloozberry MSG #25, 07-02-2011 07:01 PM
      That is essentially what sspeedstreet posted in his first picture. It is an interesting idea.

wftb (danjesso@bmts.com) MSG #26, 07-03-2011 12:10 AM
      i really want to do a double A arm rear suspension on the rear of my 86 fiero .and i have posted in other threads about this .and most supercars use this type of suspension .but in this months car and driver there is a 911 vs boxter handling comparo and the 911 wins and it uses struts all around .so who knows? maybe just more tweaking is what we need instead of wholesale changes .and Will , name me a car that has a bigger roll bar in the back .

gusshotrod (gushotrod@aol.com) MSG #27, 07-03-2011 12:43 AM
      Bigger roll bar in the back? Yenko Corvair. (After checking, they were the same size front and rear).

[This message has been edited by gusshotrod (edited 07-03-2011).]

Will (william.lucke@gmail.com) MSG #28, 07-03-2011 08:52 AM
     
 
quote
Originally posted by wftb:

Will , name me a car that has a bigger roll bar in the back .


Herb Adams recommended setting a Fiero up this way. Some people in the community have had success autocrossing/racing cars set up like that. I don't agree with Herb, but he was able to make the car fast that way.


 
quote
Originally posted by gusshotrod:

Like you said Will, it depends on everything else. Active rear steer (which would be very useful) is not allowed in any form of racing that I am aware of. Passive rear steer is not used in drag racing. In circle track it is used, but mostly to make up for lack of available tire stagger. In road racing or on the street it is useless in high horsepower cars. For lower HP cars it can be useful IF you can divorce the bump steer from the roll steer AND if the rear tires end up with more slip angle than the front suspension. The rear suspension has no need to be better than the front, as you will never be able to use the improvement. I doubt if anybody drives on the street close enough to the limit to make rear steer worthwhile. It would be much more useful to limit toe change as much as possible to improve stability.


Several of the '90's Japanese supercars (FD3S RX-7, Z32 300ZX, 3000GT VR4, R32/3/4 Skyline GTR) had active rear steering systems. Modern enthusiast frequently eliminate these systems. If there were an unequivocal benefit, I expect they'd be kept.

I'm not much of a fan of roll steer and other "passive" ways of making a car "safe". If you exercise all of your options for building understeer into a suspension design, what do you think the end result will be? Understeer. You can then tune out the understeer, but the result would be a Jekyll/Hyde driving characteristic in which the tuning and natural tendencies of the chassis are fighting each other.
That same situation was built into the 84-87 Fieros in reverse. Being a rear-heavy car with equal tire fitment, the car naturally wants to oversteer. To make it "safe", GM tuned it for understeer. The result is that it understeers to the limit and then rapidly transitions to oversteer, has a vicious list-throttle reaction and generally can't be driven hard with confidence.

I'd rather build the car from the get-go to be neutral and transparent.


 
quote
Originally posted by gusshotrod:

Bigger roll bar in the back? Yenko Corvair. (After checking, they were the same size front and rear).



I've driven a couple of Corvairs. I like them. They can be setup to be absolute weapons on an autocross course. If the cooling fan drive belt weren't so gimmicky, they'd be serious cars.

 
quote
Originally posted by sspeedstreet:

Is an SLA design possible for the rear of a Fiero? Is it worth the effort? Is there sufficient strength in the stock wheel-well to support the UCA mounting points or will it need a subframe designed? Is there room enough for links of sufficient length on the passenger side even if you built a subframe?

SLA systems exist. Bearings, bushings, ball joints, anti-squat, roll-steer . . . these are all things that can be designed in or out any way you want. They are not relevant (to me, anyway) at this point.


Questions like "can it be done?" are trivial. Of course it can be done. There are thousands of 10 and even 9 second door slammers around the country that are back-halved, caged, etc. yet still driveable on public streets. There's FAR more work involved in building one of those cars than in 99% of Fieros that hit the track.
There's no reason the same couldn't be done to a Fiero: chop off everything behind the firewall and start from scratch to build an entirely new tube frame and rear suspension. The only thing you'd keep would be the stock body panel mounting points.

Unfortunately, when most people think of that kind of work on a Fiero, they think "Lamborghini" instead of "track monster".

[This message has been edited by Will (edited 07-03-2011).]

ccfiero350 (chuckcamp@gmail.com) MSG #29, 07-03-2011 09:09 AM
      Porsche really does strut type suspensions better then anybody. They have been at it a while.

I did an x-cross once in the fiero with an ADCO rear bar and the stock front bar and found that it was much more eager to turn in, almost tail happy.

I do think it's possible to do a SLA rear, the real head scratcher will be the upper A-arm mounting base like others have said. The lower rear frame horn in that area would not take too kindly to that kind of side load.

But, it being a rear end after all, the real goal is better camber gain, just a little, a couple of degrees worth.

I would take advantage of the structure of the upper strut mount area and mount my upper A-arm there and make an adapter for my knuckle to place the BALL JOINT above and outside the wheel. It would require a strut bar to keep things in check, but it's now its in an easer area to deal with. The strut will need to be de-coupled from the knuckle by a clevis type of connection. This is a pretty common modern type of strut application.




Will (william.lucke@gmail.com) MSG #30, 07-03-2011 09:25 AM
     
 
quote
Originally posted by ccfiero350:

Porsche really does strut type suspensions better then anybody. They have been at it a while.

I did an x-cross once in the fiero with an ADCO rear bar and the stock front bar and found that it was much more eager to turn in, almost tail happy.

I do think it's possible to do a SLA rear, the real head scratcher will be the upper A-arm mounting base like others have said. The lower rear frame horn in that area would not take too kindly to that kind of side load.

But, it being a rear end after all, the real goal is better camber gain, just a little, a couple of degrees worth.

I would take advantage of the structure of the upper strut mount area and mount my upper A-arm there and make an adapter for my knuckle to place the BALL JOINT above and outside the wheel. It would require a strut bar to keep things in check, but it's now its in an easer area to deal with. The strut will need to be de-coupled from the knuckle by a clevis type of connection. This is a pretty common modern type of strut application.


Don't forget that BMW does a lot with struts as well. There's nothing "wrong" with the concept of a strut suspension. It just has to be executed well. As Gordon Murray said "The automotive problem is fundamentally one of packaging".

The tall knuckle you describe is actually pretty terrible for camber gain. Think about the lateral distance the upper ball joint would have to cover to create a given camber change vs. the lateral distance that the UBJ would have to cover on a conventional knuckle inside the wheel.

What the tall knuckle geometry does is let designers *PACKAGE* a SLA setup in almost the same volume as a strut and get better kingpin axis packaging. That's the same reason that some MFG's use "virtual kingpin" type geometries... BMW's done that in the 5, 6 & 7 series for years, 2G DSM lower control arms are like that, as are some Audi designs. This isn't done for any geometric advantage... it's done for packaging.

Also, the tall knuckle adds significant unsprung weight.

[This message has been edited by Will (edited 07-03-2011).]

Will (william.lucke@gmail.com) MSG #31, 07-03-2011 09:27 AM
     
 
quote
Originally posted by ccfiero350:
The lower rear frame horn in that area would not take too kindly to that kind of side load.



Why not?
(Hint: Where is most of the lateral load of the current rear suspension applied?)


ccfiero350 (chuckcamp@gmail.com) MSG #32, 07-03-2011 09:38 AM
      Sorry to confuse, the sub frame handles all the point loads, spread them out and re-distribute them, the frame horn is what the sub frame bolts to. The frame horns are more about holding up that end of the car and crumble zones. If you can dent it with a small ball pein, it's probably not suited to hold a point load.



Marvin McInnis MSG #33, 07-03-2011 12:35 PM
     
 
quote
Originally posted by sspeedstreet:

This is why this forum wears me down sometimes. An idea is proposed for discussion and immediately people jump in with minutiae.



You want a simple solution to a complex problem. Such simple solutions sometimes exist in the real world, but not always. You have to understand a problem thoroughly to be able to decide if a given solution is "good enough." In the case of the Fiero, if the problem were trivial somebody would almost certainly already have done it.

[This message has been edited by Marvin McInnis (edited 07-03-2011).]

wftb (danjesso@bmts.com) MSG #34, 07-03-2011 03:14 PM
      the rear sway bar option is something i have not bothered with .my car does not have one and handles really well with the mods and tires that i have put on .i have herb's book and it has been a big help .reading about his sway bar set up today gave me the impression it would not work properly without the bushing mods that were mentioned in most of the articles .the main reason i would like to have an upper A arm in the rear suspension would be to be able to get rid of the rear tie rods .these cause the up and down toe changes that give bump steer .i am slowly building a locost 7 and i have the front end completed and the locost usa forum has lots of builds that have adapted strut hubs to A arms .i keep thinking about buying the held bump steer kit but it does not eliminate the tie rod completely and i think i can do better .

ccfiero350 (chuckcamp@gmail.com) MSG #35, 07-03-2011 05:15 PM
      I'm thinking Herb Adams train of thought on the big rear sway bar was to limit the camber/toe change by increasing rear roll stiffness. When I did this to my 88 car it had very nice turn in manners. I did not get a chance to try it out on a long sweeper though, wish I did.

Did Herb Adams do any work on 88s ?



ccfiero350 (chuckcamp@gmail.com) MSG #36, 07-03-2011 05:45 PM
     
 
quote
Originally posted by Will:

What the tall knuckle geometry does is let designers *PACKAGE* a SLA setup in almost the same volume as a strut and get better kingpin axis packaging. That's the same reason that some MFG's use "virtual kingpin" type geometries... BMW's done that in the 5, 6 & 7 series for years, 2G DSM lower control arms are like that, as are some Audi designs. This isn't done for any geometric advantage... it's done for packaging.



Kingpin angle determines how much lift and it's effect on camber when you turn. On the front end, its very important, on the rear, not so unless your designing forklifts. You don't need a lot of camber gain for the rear, just enough to counteract the roll, and you want a little toe to direct your thrust angle where you best like it.



Tha Driver MSG #37, 07-04-2011 08:19 AM
      I was thinking about making upper control arms for the rear of my solo car (if I ever get the time & money to finish it). It's an '88: I was thinking simply weld brackets to the frame rail (plate it first of course) & bolt an upper A arm (or two heim ended arms) to it & the lower strut hole (as the pivot). You could use the upper strut hole for a coilover shock mount.
Can anyone with a good program make an animation of that & see if that a arm will be the right length? (or how far off it is - it's probably going to be short)
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts


Will (william.lucke@gmail.com) MSG #38, 07-04-2011 08:43 AM
     
 
quote
Originally posted by ccfiero350:

Sorry to confuse, the sub frame handles all the point loads, spread them out and re-distribute them, the frame horn is what the sub frame bolts to. The frame horns are more about holding up that end of the car and crumble zones. If you can dent it with a small ball pein, it's probably not suited to hold a point load.



If you're going to anchor your upper control arm to the lower frame rail, I think it's pretty clear you'd want to fabricate a weld-in mount that can take the point loads from the control arm pivots.


 
quote
Originally posted by ccfiero350:

Kingpin angle determines how much lift and it's effect on camber when you turn. On the front end, its very important, on the rear, not so unless your designing forklifts. You don't need a lot of camber gain for the rear, just enough to counteract the roll, and you want a little toe to direct your thrust angle where you best like it.


Yep... and you suggested a tall knuckle for the rear. I was discussing why it's used and in what applications... It's used for packaging steering geometry and has significant drawbacks in terms of camber gain. I don't think it's a good thing to use in the rear of anything, much less a Fiero.


Will (william.lucke@gmail.com) MSG #39, 07-04-2011 08:50 AM
     
 
quote
Originally posted by wftb:

Will , name me a car that has a bigger roll bar in the back .


Also, do you know *WHY* most cars have the larger bar in the front?

It has to do with weight distribution and the relationship of the centroid axis to the roll axis...

IE, "conventional wisdom" pretty much expects that the HEAVY end of the car will get the bigger bar.

Also, bigger bars make chassis tuning problems... not necessarily better handling.

[This message has been edited by Will (edited 07-04-2011).]

Black Lotus MSG #40, 07-04-2011 12:47 PM
      Awhile back I made some measurements of the front and rear suspension pivot points on my '88 for a suspension program that I have.
The front roll center was a little bit HIGHER than the rear roll center. (WTF!) By eyeballing where the masses were in the car, it suggested to me that the roll center axis was out of whack with the mass axis of the car. In other words, this means the the rear overturning rolling moment was much higher than the front and explained the need for the rather large stock anti-roll bar in the back of the Fiero.
Not that this is entirely bad, as it might help the car pass whatever dynamic steering quality tests that the car had to go thru to pass GM steering and stability tests (maybe).
This would explain the feeling that the back end of the car would flop over a bit, even with Koni shocks, which was a real party killer to me because I wanted to put a big 'ol Chevy V8 in it. A big V8 would have made the car scary at the limit, or when recovering from a slide.
The only solution I could see was to put a LOT lighter engine in the back--or lower the existing package-- and raise the rear roll center.
(I would have used this opportunity to remove more weight from the front to keep the weight distribution the same, as that is just fine.)
However, raising the rear roll center puts more lateral load onto the outside rear tire in a corner and makes the car fundamentally more prone to oversteer.
Reducing or eliminating the the rear bar to compensate for the raised rear roll center aggravates the lack of rear suspension travel and would make the rear end more prone to hitting the bumpstops.
What a mess!
At this point, the EASIEST thing to do, because I am lazy, was to put all-season tires on it and and buy a different car for serious driving.






Will (william.lucke@gmail.com) MSG #41, 07-04-2011 09:01 PM
     
 
quote
Originally posted by Black Lotus:
However, raising the rear roll center puts more lateral load onto the outside rear tire in a corner and makes the car fundamentally more prone to oversteer.



Not really...
-The equation for weight transfer includes Cg height, track width and lateral G.
-Raising the rear roll center reduces the rear roll moment by shortening the moment arm between the centroid axis and the roll axis.
-A rear-heavy car with minimal tire stagger will *ALWAYS* be prone to oversteer, no matter how good the suspension is. The way to fix this is with tire sizes, not suspension geometry or tuning.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #42, 07-07-2011 03:12 AM
     
 
quote
Originally posted by sspeedstreet:

This is why this forum wears me down sometimes. An idea is proposed for discussion and immediately people jump in with minutiae. As in details that are of no consequence at the point of discussing the feasibility of an idea. Is an SLA design possible for the rear of a Fiero? Is it worth the effort? Is there sufficient strength in the stock wheel-well to support the UCA mounting points or will it need a subframe designed? Is there room enough for links of sufficient length on the passenger side even if you built a subframe? I don't know about your cars, but mine has an alternator pulley up against the inside of the wheel-well.

SLA systems exist. Bearings, bushings, ball joints, anti-squat, roll-steer . . . these are all things that can be designed in or out any way you want. They are not relevant (to me, anyway) at this point.

As for my comment "Really, a ball joint is a type of spherical bearing? A Ferrari and a Prius are both automobiles, but their benefits are not interchangeable.". There needs to be a sarcasm font. Of course I know a ball joint is a type of spherical bearing, but they each have there own application.

I guess I just hate to be lectured to.


Thank you! At least one person understands the idea behind this thread. Hopefully we can get back on track and discuss the major parts of suspension design prior to minutia of ball-joints, heim joints, etc.

Stuff like this below is the beginning of what I had in mind for this thread:
 
quote
Originally posted by sspeedstreet:
I've been thinking of the same things. I was looking at the Mustang SLA setup as well. The Fiero design [...snip...] would need the strut pickup on the upright moved to clear the axle. To the side or my choice:


This animation shows a rocker type strut instead of the stock Fiero position, but you get the idea:


(Credit to dave@team321.com)



Bloozberry MSG #43, 07-07-2011 07:17 AM
      Interesting, because if that's what you wanted, then your opening post shouldn't have lead us astray by stating you wanted:

 
quote
Originally posted by Austrian Import:

to DESIGN a more modern
A ) Double wishbone front + Double wishbone rear
B ) Double wishbone front + fancy multi-link rear
C ) another option I hadn't considered.



and:

 
quote
Originally posted by Austrian Import:

The goal is to APPLY what engineers have learned about suspension design in the last 30 years since the Fiero was built.


and:

 
quote
Originally posted by Austrian Import:

Reasons I thought it would be a great idea to do this:
1) It is a great way to learn/share ideas about modern suspension THEORY
2) Learn suspension DESIGN applied to a specific project (with applied constraints),

4) provide an avenue to share TECHNICAL INFORMATION/CONTENT for people with similar interests.


Almost all of the posts in this thread to date have been in accordance with what you stated you wanted in your opening post. Am I (and nearly everyone else) missing something here?


sspeedstreet (sspeedstreet@verizon.net) MSG #44, 07-07-2011 12:18 PM
     
 
quote
Originally posted by Bloozberry:

Interesting, because if that's what you wanted, then your opening post shouldn't have lead us astray by stating you wanted:

Almost all of the posts in this thread to date have been in accordance with what you stated you wanted in your opening post. Am I (and nearly everyone else) missing something here?


Yes.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #45, 07-07-2011 12:49 PM
      I guess what I was hoping for was models of suspension designs and then discussing the benefits/drawbacks of each.
I also was hoping to start in more general terms and then get into the details as the thread progresses. It seemed to me that talking about balljoints, is like "dotting the i's" before we have figured out geometry designs in rough form.

And yes, I'm not dismissing a strut type setup, IF it's a better setup than other choices.

What I'm hoping for eventually is simulations of various suspension designs (with regards to feasability on a Fiero) from which we can discuss the benefits/drawbacks of each.



Austrian Import (maximilian_ledworowski@csumb.edu) MSG #46, 07-07-2011 01:07 PM
      These articles are pretty similar to articles that got me thinking about suspension designs in the first place:

http://www.modified.com/tec...ck_part_1/index.html
http://www.modified.com/tec...ck_part_2/index.html
http://www.modified.com/tec...ck_part_3/index.html
http://www.modified.com/tec...ck_part_4/index.html
http://www.modified.com/tec...ck_part_5/index.html
http://www.modified.com/tec...ck_part_6/index.html

http://www.rc-truckncar-tun...com/roll-center.html

I copied the pictures out of the articles for easy reference. I think they explain the basics well and should help get everybody on the same page.
I hope we will be able to find Fiero specific suspension pictures to use as a baseline for discussions. (Hope the Factory manual has these)





























[This message has been edited by Austrian Import (edited 07-07-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #47, 07-07-2011 01:30 PM
      Another good suspension primer: http://www.mae.ncsu.edu/kla...nDesignCaseStudy.ppt

BMW suspension: http://www.e30m3project.com...oll_center/index.htm

Roll center article: http://www.neohio-scca.org/...e%20Dynamics2007.pdf

Good books on the topic:
http://books.google.com/boo...#v=onepage&q&f=false
http://www.amazon.com/How-M...d=1310059392&sr=1-11 <-- ancient book, but still one of the best.
http://www.amazon.com/Compe...d=1310059448&sr=1-28
http://www.amazon.com/Autom...d=1310059468&sr=1-44
http://www.amazon.com/Vehic...d=1310059488&sr=1-54
http://www.amazon.com/Suspe...d=1310059513&sr=1-72


Bloozberry MSG #48, 07-07-2011 06:30 PM
     
 
quote
Originally posted by Austrian Import:

I hope we will be able to find Fiero specific suspension pictures to use as a baseline for discussions. (Hope the Factory manual has these)


OK, now you're talking. I'll be glad to contribute if this is going to be a structured analysis of suspension system performance. IMHO, this is the way any suspension improvement should be undertaken; by defining the limitations of the status quo, then determining if there are improvements that can be made, and how they can be implemented. Whether that involves minor tweaks or whole scale redesign isn't something that should be determined until you know what the current system does. How else could anyone possibly know that another system is better? I lack the ability to judge the performance of a system by its looks, though some seem to be able to do so.

So, to get the ball rolling in the direction you want, I'll repost the drawings of the '88 rear suspension geometry from my build thread. They're not 100% accurate, but I spent roughly 150 hours measuring and drafting the rear suspension system on an '88 to come up with them. The accuracy is within GM's own stated frame alignment tolerances of plus or minus 3 mm. I doubt you'll find official factory drawings or data. None of the service manuals have this information, neither did an exhaustive search of the internet turn up anything, and GM Customer Services said they no longer have the information either (yeah right).

'88 Stock Rear Suspension Rear View


'88 Stock Rear Suspension Side View


'88 Stock Rear Suspension Top View


Determination of Stock '88 Rear Suspension Roll Center


Determination of Stock '88 Rear Suspension Dynamic Roll Centers


Determination of Stock '88 Rear Suspension % Anti Squat


Determination of Stock '88 Rear Suspension Camber Change


Determination of Stock '88 Rear Suspension Toe Change



sspeedstreet (sspeedstreet@verizon.net) MSG #49, 07-07-2011 08:53 PM
      Bloozberry, those drawings are superb! That's more Fiero rear suspension data in one spot than the total I'd ever seen before. Thanks for posting those for us. Honest, I will shut up and listen to what you have to offer.

A question: In your "Determination of Stock '88 Rear Suspension Camber Change" diagram, you are showing lateral link parallel with the ground and 0 degree camber at the static ride height. At 76mm jounce the tire actually moves into negative camber? Is this due to the angle of the strut axis during compression? I guess that's why the '88 was redesigned with the upper strut mount moved inward? Well, I had that all wrong in my head.

Also interesting is how the roll center drops like a stone as the suspension is compressed. That's why my car seemed to have a rapidly increasing body roll as I pushed harder in the corners. Self-actuating roll. Now I see the real benefit of SLA setups; less to do with camber (as I had thought) and more to do with body roll.

Thanks again, I've been schooled.

~Neil


Bloozberry MSG #50, 07-07-2011 10:36 PM
     
 
quote
Originally posted by sspeedstreet:

A question: At 76mm jounce the tire actually moves into negative camber? Is this due to the angle of the strut axis during compression?


Yes, the tire moves into negative camber, but the "still" pictures only tell part of the story. First, you have to consider that the static camber on a Fiero rear alignment is set at -1.0*, not zero as I have depicted it. So to get real world values, you have to subtract 1.0* from the camber angles shown in both rebound and jounce too. Then, consider that the Macpherson strut is designed to gain negative camber as long as the lower control arm and strut axis form an angle of less than 90 degrees. Although it's hard to measure this angle in the posted version of the drawings, I can do it on the originals much easier. What it shows is that from 76mm rebound (full extension) the angle between the lower control arm and the strut axis is about 64*, so as it travels upwards from there in jounce, it gains negative camber, ie the camber angle of the wheel moves from +2.2* towards zero. By the time the suspension is at 76mm jounce (full compression), the angle between the lower control arm and the strut axis is up to 85*, but not yet past 90*. This means that the camber curve remains on the correct side of 90* between these two limits of jounce and rebound, but the rate of camber change reduces quickly as you near full jounce. If improvements could be made, I would increase the rate at which the camber changes between the two limits.

 
quote
Originally posted by sspeedstreet:

I guess that's why the '88 was redesigned with the upper strut mount moved inward?


Exactly.


Knight MSG #51, 07-07-2011 11:55 PM
      I am so excited reading this thread. I have been wondering how we can make our cars handle as well as any non exotic sports car without removing so much that its not really a Fiero anymore. I can't wait to see where this thread goes. I just love this car so much that I want to impress others with how great a car the Fiero is.

I love this site and all the truely knowledgeable people on it.

Anybody got any info on the 84-87 like Bloozberry has on the 88? Or is the 84-87 rear beyond hope?

[This message has been edited by Knight (edited 07-07-2011).]

Knight MSG #52, 07-08-2011 12:19 AM
      Would a multi-link upper instead of an upper control arm work, to get around the space limitations on the passenger side? Might have to relocate the battery.
Sorry, my car is out of town for the next 7 weeks so I can't eyeball anything.

Would tilting the cradle on the 84-87 help with squat? I know that I would have to modify the engine mounts to level the engine/trans. I already plan on relocating the outer tie rod attachment points to minimize bump steer. If Bump steer and pro-squat rear characteristics could be fixed, would the 88 be much of a noticeable improvement to be worth the effort for a cradle swap? Let's assume poly suspension bushings and solid metal cradle mounts. Still have to deal with 84-87 front suspension as I hear a 88 front swap is too much of a PITA.

Any thoughts?


kennn (kbrooksarchitect@cox.net) MSG #53, 07-08-2011 11:11 PM
      For me the question that is begged is, could the front roll center be lowered? For the upper A-arm on the '88, the inside pivot looks to be higher at rest than the ball joint/knuckle joint. If the inside pivot could be lowered, wouldn't that also lower the front roll center and provide a more beneficial camber change curve?

Edit: Two things: First, it appears in essence that's what ccfiero350 has done with the Saturn knuckle and new upper A-arm; Second, I neglected to see that there was a whole second page. Sorry.

Ken



Will (william.lucke@gmail.com) MSG #54, 07-09-2011 07:42 AM
     
 
quote
Originally posted by Bloozberry:

Yes, the tire moves into negative camber, but the "still" pictures only tell part of the story.



Another part of the story is the loss of camber through bushing compression.


ccfiero350 (chuckcamp@gmail.com) MSG #55, 07-09-2011 01:03 PM
     
 
quote
Originally posted by Bloozberry:


This is the way any suspension improvement should be undertaken; by defining the limitations of the status quo, then determining if there are improvements that can be made, and how they can be implemented. Whether that involves minor tweaks or whole scale redesign isn't something that should be determined until you know what the current system does. How else could anyone possibly know that another system is better?



Yep, Bloozberry hit it on the head. I would start out a kinematic study with some animations of the stock 88 setup, then one thats lowered, then another with some simple mods that most people can do, then one with mods that only a handful of people crazy enough will try.



Knight MSG #56, 07-11-2011 01:23 AM
      Bump for an awesome thread. Please people, put forth some ideas.

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #57, 07-15-2011 03:19 PM
     
 
quote
Originally posted by Bloozberry:


OK, now you're talking. I'll be glad to contribute if this is going to be a structured analysis of suspension system performance. IMHO, this is the way any suspension improvement should be undertaken; by defining the limitations of the status quo, then determining if there are improvements that can be made, and how they can be implemented. [..] SNIP
[...]


Yea, that's what I meant originally. Maybe I should have specified better at the beginning. I guess that's why threads are "living documents" that grow with each contribution. Glad to see I'm not the only one interested in this.


sspeedstreet (sspeedstreet@verizon.net) MSG #58, 07-15-2011 03:40 PM
      I have another auto-cross on the 23rd an will get some close-up video of the car in the corners. I just finished installing my poly-Delrin custom toe and lateral rear links and had it aligned (1.5* negative camber, 1/8" toe-in), so I don't expect the suspension deflection to be a big factor this time. We'll see what the rear looks like under load.

sspeedstreet (sspeedstreet@verizon.net) MSG #59, 07-27-2011 12:30 AM
      This is the best shot I got of the suspension compressed in a corner. Stock swaybars with poly mounts and heim joint ends, 280 lb/in front springs and 350 lb/in rears, Koni shocks, all poly on the rear links, stock bushings on the front and and stock tire sizes all around (Yoko AVIDs). The car is lowered 1.5 inches in the front and 1.0 inch in the rear.



The car was neutral with under or over steer easily induced (over steer VERY easy to induce). The tires seemed to be wearing evenly all around as there didn't seem to be a lot of positive camber in the corners. There is a lot of body roll however and this leads to a tail happy condition when power is applied. So there it is, The camber curve isn't the problem, it's the falling roll center (which I am just now getting my head around).

A couple of vids:

http://www.youtube.com/watch?v=o93DBadnHWs

http://www.youtube.com/watch?v=VyAc6YPGBa0

[This message has been edited by sspeedstreet (edited 07-27-2011).]

Will (william.lucke@gmail.com) MSG #60, 07-27-2011 07:07 AM
     
 
quote
Originally posted by sspeedstreet:

This is the best shot I got of the suspension compressed in a corner. Stock swaybars with poly mounts and heim joint ends, 280 lb/in front springs and 350 lb/in rears, Koni shocks, all poly on the rear links, stock bushings on the front and and stock tire sizes all around (Yoko AVIDs). The car is lowered 1.5 inches in the front and 1.0 inch in the rear.

http://i17.photobucket.com/...street/Tightleft.jpg

The car was neutral with under or over steer easily induced (over steer VERY easy to induce). The tires seemed to be wearing evenly all around as there didn't seem to be a lot of positive camber in the corners. There is a lot of body roll however and this leads to a tail happy condition when power is applied. So there it is, The camber curve isn't the problem, it's the falling roll center (which I am just now getting my head around).

A couple of vids:

http://www.youtube.com/watch?v=o93DBadnHWs

http://www.youtube.com/watch?v=VyAc6YPGBa0




*ANY* discussion of suspension that doesn't begin and end with tires is meaningless.


sspeedstreet (sspeedstreet@verizon.net) MSG #61, 07-27-2011 10:58 AM
     
 
quote
Originally posted by Will:

*ANY* discussion of suspension that doesn't begin and end with tires is meaningless.


You stopped me with that one. Please explain.



bse53 MSG #62, 07-27-2011 12:08 PM
      If you're going to view camber changes throughout suspension travel, try putting the camera under the car, like this video, using an inexpensive 'spy' camera:

http://www.youtube.com/watch?v=R4N3r1u_K_Y


This is a great thread for me, as I just purchased a dedicated autocross Fiero. I just ordered a couple of cameras like the one used in the video. It might help me understand what's happening as I try different ride heights.


I'm guessing the focus of the thread though, is in street driven, performance oriented designs.


Will (william.lucke@gmail.com) MSG #63, 07-27-2011 01:55 PM
     
 
quote
Originally posted by sspeedstreet:

You stopped me with that one. Please explain.


You didn't mention what size tires you have.
There's basically nothing you can do about oversteer on a rear-heavy car with a square tire fitment, for example.

Tires make a car handle. Period.
The only reason to concern ourselves with suspension design is to make the best use of the tires.

[This message has been edited by Will (edited 07-27-2011).]

ccfiero350 (chuckcamp@gmail.com) MSG #64, 07-27-2011 02:11 PM
     
 
quote
Originally posted by sspeedstreet:

This is the best shot I got of the suspension compressed in a corner. Stock swaybars with poly mounts and heim joint ends, 280 lb/in front springs and 350 lb/in rears, Koni shocks, all poly on the rear links, stock bushings on the front and and stock tire sizes all around (Yoko AVIDs). The car is lowered 1.5 inches in the front and 1.0 inch in the rear.


Looks like he did mention his tires, maybe because it was not the first or last thing he wrote about, it was in the middle.



sspeedstreet (sspeedstreet@verizon.net) MSG #65, 07-27-2011 02:42 PM
      All righty. 205/60/15 fronts on 6.5" rims, 215/60/15 on 7.0" rims at the rear.

bse53 MSG #66, 07-27-2011 03:09 PM
      "There's basically nothing you can do about oversteer on a rear-heavy car with a square tire fitment, for example."

Is this always true? Can't I just stiffen up the front until it understeers, stiffen up the back until it oversteers, then back off a bit on the rear?

Aren't staggered tire sizes just one of the many compromises?

Isn't this thread about designing a suspension that doesn't necessarily require that design compromise?

I'm asking the question, because I'm going to try a square setup on my autocross car, going from 10" front- 12" rear wheels to 10" all around.


Will (william.lucke@gmail.com) MSG #67, 07-27-2011 05:23 PM
     
 
quote
Originally posted by bse53:

"There's basically nothing you can do about oversteer on a rear-heavy car with a square tire fitment, for example."

Is this always true? Can't I just stiffen up the front until it understeers, stiffen up the back until it oversteers, then back off a bit on the rear?

Aren't staggered tire sizes just one of the many compromises?

Isn't this thread about designing a suspension that doesn't necessarily require that design compromise?

I'm asking the question, because I'm going to try a square setup on my autocross car, going from 10" front- 12" rear wheels to 10" all around.


For a car with other than 50/50 weight distribution, staggered is the ideal. Tire width should match the weight distribution. Square is the compromise (usually in the name of lower cost).

If you tune the suspension against the natural tendency you get from the contact pressure balance front/rear, then you get what the Fiero was stock... understeer up to the limit, then rapid transition to oversteer.


bse53 MSG #68, 07-28-2011 11:23 AM
      Speedstreet-

Looking at your picture, it appears the rear tire has moved into positive camber, as has the front.

This discussion seems to be focusing on the rear suspension, but the front suspension has it's own issues.

I realize the thrust of this thread relates to engineering a suspension, but I would look at the S2000 suspension. The S2000 owns BS in autocross, replacing the C4 Corvette as the car to own.

In your design I wouldn't ignore the weight distribution issue either. I'd be moving the rear wheel as far back as I could given the limitation of the engine transmission package.


Will (william.lucke@gmail.com) MSG #69, 07-28-2011 12:37 PM
     
 
quote
Originally posted by bse53:
I'm asking the question, because I'm going to try a square setup on my autocross car, going from 10" front- 12" rear wheels to 10" all around.


What problem are you trying to solve with this change?


bse53 MSG #70, 07-28-2011 01:00 PM
      Narrow is good in autocross, all things being equal. As you can see, the 12" wheels (with 5.5" backspace) stick out a ways. 10" wheels narrow the car by 4".

12" wheels require racing slicks (there are no autocross size 15" tires to fit) and consequently I'm not sure I can build heat quick enough to make use of the potential extra grip of the wider tires.



Brian



sspeedstreet (sspeedstreet@verizon.net) MSG #71, 07-28-2011 01:25 PM
      I have no interest in dedicating my car to track use only . Wide sticky tires, stiffer springs and higher rate sway bars only mask an inherently poor suspension design. Reducing body roll by design would be my goal. Then the spring rate in the rear could be reduced to make the car stick better in wet or uneven road surfaces i.e., The Real World.

bse53 MSG #72, 07-28-2011 01:46 PM
      sspeedstreet,

I'm not trying to highjack this thread, which I find fascinating, and autocrossing a stock car is just as much fun as a modified one-- but for different reasons.

I was autocrossing a c4 Corvette in AS (now BS). As you are aware stock classes severely limit your ability to modify the car-- the only alterations are shocks, front sway bar and tires. To be competitive in stock classes, you'll need the biggest sticky tires you can stuff on stock rims and stiff shocks on rebound. Don't think a bigger front bar would help.
I think you probably want more static negative camber- both front and rear.

I'll keep quiet now, and hopefully the discussion will resume about how to improve the Fiero's suspension.


Will (william.lucke@gmail.com) MSG #73, 07-28-2011 02:01 PM
     
 
quote
Originally posted by bse53:

Narrow is good in autocross, all things being equal. As you can see, the 12" wheels (with 5.5" backspace) stick out a ways. 10" wheels narrow the car by 4".

12" wheels require racing slicks (there are no autocross size 15" tires to fit) and consequently I'm not sure I can build heat quick enough to make use of the potential extra grip of the wider tires.

http://i152.photobucket.com...se53/06222011317.jpg

Brian


Are you having oversteer problems because your rear tires are too cold?

 
quote
Originally posted by sspeedstreet:

I have no interest in dedicating my car to track use only . Wide sticky tires, stiffer springs and higher rate sway bars only mask an inherently poor suspension design. Reducing body roll by design would be my goal. Then the spring rate in the rear could be reduced to make the car stick better in wet or uneven road surfaces i.e., The Real World.


"Wide sticky tires... mask an inherently poor suspension design"
Say what?

Flat cornering is not the same as good handling...
A Lotus Elise/Exige is one of the best handling cars on the market, yet has a lot of body roll by modern standards.

Also remember that gokarts corner flat and have NO suspension.

[This message has been edited by Will (edited 07-28-2011).]

sspeedstreet (sspeedstreet@verizon.net) MSG #74, 07-28-2011 02:29 PM
      By mask I mean be capable of more lateral g than, say, a street tire. Take any suspension design, good or bad. Will it produce better lap times on typical street tires or race tires? Does that mean the suspension becomes better at controlling the contact patch because it has wider, sticky tires? No, it only means the shortcomings of a given design become apparent at a higher limit.

bse53 MSG #75, 07-28-2011 02:30 PM
      Funny you should ask about heat in the tires.

When I got the car, it had some old hard racing slicks. I bought some tak-offs from a guy in Michigan that were supposedly fresh.

The car understeered like a pig-- that is until it spun out. Totally unpredictable. I worked the understeer out (somewhat), but I was still way behind where I should be time wise, based on the history of the car. My assumption was that I wasn't getting heat in the tires, since it's been a cold spring and the car came from Arizona where heat in the tires isn't an issue.

Talked to the supplier in Michigan and he sent me out another set-- but this time 4 9.5" slicks. I crammed them on some 8" stock rims and even as pinched as they were, the difference was night and day.

The first set he sent me were already cycled out, even though they still had plenty of tread.

Since I only have two 10" rims, I'm going to put two of the newer tires on those and put the 8" wheels up front (effectively leaving me with some stagger).

But I still think the narrower wheels may be faster.

As to body roll-- the most impressive car I see autocrossing are the BMW's in stock classes. They have lots of body roll and are incredibly quick cars. It's rather amazing actually.

Another reason why I'd look at the S2000 geometry though, is the "in-wheel" design.


Will (william.lucke@gmail.com) MSG #76, 07-28-2011 05:06 PM
     
 
quote
Originally posted by sspeedstreet:

By mask I mean be capable of more lateral g than, say, a street tire. Take any suspension design, good or bad. Will it produce better lap times on typical street tires or race tires? Does that mean the suspension becomes better at controlling the contact patch because it has wider, sticky tires? No, it only means the shortcomings of a given design become apparent at a higher limit.


A car with great tires and crappy suspension will out drive a car with great suspension and crappy tires.

Tires > suspension

Also, if you put a specific type/size/stagger of tire on a car, dial in the suspension, then change to significantly different type/size/stagger, you'll have to retune the suspension.

It's all part of the package. Getting max performance involves matching everything. The matching process has to begin and end with tires.

[This message has been edited by Will (edited 07-28-2011).]

Will (william.lucke@gmail.com) MSG #77, 07-28-2011 05:16 PM
     
 
quote
Originally posted by bse53:

Funny you should ask about heat in the tires.

When I got the car, it had some old hard racing slicks. I bought some tak-offs from a guy in Michigan that were supposedly fresh.

The car understeered like a pig-- that is until it spun out. Totally unpredictable. I worked the understeer out (somewhat), but I was still way behind where I should be time wise, based on the history of the car. My assumption was that I wasn't getting heat in the tires, since it's been a cold spring and the car came from Arizona where heat in the tires isn't an issue.

Talked to the supplier in Michigan and he sent me out another set-- but this time 4 9.5" slicks. I crammed them on some 8" stock rims and even as pinched as they were, the difference was night and day.

The first set he sent me were already cycled out, even though they still had plenty of tread.

Since I only have two 10" rims, I'm going to put two of the newer tires on those and put the 8" wheels up front (effectively leaving me with some stagger).

But I still think the narrower wheels may be faster.

As to body roll-- the most impressive car I see autocrossing are the BMW's in stock classes. They have lots of body roll and are incredibly quick cars. It's rather amazing actually.

Another reason why I'd look at the S2000 geometry though, is the "in-wheel" design.



There certainly can be such a thing as too much tire, depending on the weight of the car, tire compound, time available to build heat, etc.

I agree that an "in-wheel" knuckle on a SLA suspension is better than a "tall knuckle" with the UBJ above the top of the tire.

What you said about BMW's basically defines good geometry... allows the car to make the best use of its tires. Traction makes a car quick. The quickest car is the car that's able to exercise the most traction throughout the course. Exercising traction involves making the best use of your tires.


KurtAKX MSG #78, 07-29-2011 08:56 AM
     
 
quote
Originally posted by bse53:

Narrow is good in autocross, all things being equal. As you can see, the 12" wheels (with 5.5" backspace) stick out a ways. 10" wheels narrow the car by 4".



Narrow is good. It's interesting to watch just how much less a narrow car has to work through an autocross slalom than a wide car.


bse53 MSG #79, 07-29-2011 09:35 AM
      One of the better autocross drivers did an analysis of what are the important elements needed in an autocross run. Here's the breakdown of a 59.18 second run at a national event:
Transitions: 24.27 seconds, 41.01%

Skidpad: 23.25 seconds, 39.29%

Entry: 5.16 seconds, 8.72%

Pure Accel: 3.67 seconds, 6.2%

Pure Braking: .59 seconds, 1%

And if you further boil those down you get these:

Primarily turning: 80.3%

Primarily slowing down: 9.72%

Primarily speeding up: 9.99%

Narrow helps in transitions. Low cg and track width helps with skidpad.

Byron Short did the math in transitions. Car A is 66" wide. Car B is 72.5" wide. Assuming the same lateral g's, car A will have a .2 second advantage after 5 cones.
Any autocrosser would benefit from reading his analysis.

http://www.rhoadescamaro.com/build/?page_id=481

For that matter, looking at his next car.


Will (william.lucke@gmail.com) MSG #80, 07-30-2011 09:23 PM
     
 
quote
Originally posted by sspeedstreet:

I have no interest in dedicating my car to track use only . Wide sticky tires, stiffer springs and higher rate sway bars only mask an inherently poor suspension design. Reducing body roll by design would be my goal. Then the spring rate in the rear could be reduced to make the car stick better in wet or uneven road surfaces i.e., The Real World.


 
quote
Originally posted by sspeedstreet:

By mask I mean be capable of more lateral g than, say, a street tire. Take any suspension design, good or bad. Will it produce better lap times on typical street tires or race tires? Does that mean the suspension becomes better at controlling the contact patch because it has wider, sticky tires? No, it only means the shortcomings of a given design become apparent at a higher limit.


I agree that a good suspension design makes the best use of the tires.
It does this by keeping the relationship of the tire to the pavement such that contact pressure is even across the face of the tire despite body roll and lateral squirm of the tire when loaded.

I do not agree that the geometry should be used to limit body roll. This deprives the driver of the ability to feel the chassis load up.

The shortcomings of a given design will become apparent with appropriate testing and observation... such as using a pyrometer to measure surface temps across the width of the tread or observing tire wear patterns.


Will (william.lucke@gmail.com) MSG #81, 07-30-2011 09:24 PM
     
 
quote
Originally posted by bse53:

One of the better autocross drivers did an analysis of what are the important elements needed in an autocross run. Here's the breakdown of a 59.18 second run at a national event:
http://www.rhoadescamaro.com/build/?page_id=481

For that matter, looking at his next car.


That looks like a really cool resource... I'll have to check it out in a couple of weeks when I can sleep...


retroman (gnatsum64@yahoo.com) MSG #82, 07-30-2011 09:38 PM
      I understand that discussion is an important part of development, but I really want to see pictures of a fully modern suspension on a Fiero. There are a lot of supercars out there from which we can draw. Personally, I like the setup on the Ford GT. Anyway, I'm no engineer, so I guess I'll shut up now and let some more brilliant minds come up with a solution. I know I've been impatient, but I really want to see the end product.

sspeedstreet (sspeedstreet@verizon.net) MSG #83, 07-31-2011 02:16 AM
     
 
quote
Originally posted by Will:

I do not agree that the geometry should be used to limit body roll. This deprives the driver of the ability to feel the chassis load up.


I couldn't agree more. My point is that the McPherson strut design is limited by its inability to keep the contact patch intact during jounce and rebound. In order to keep the patch on the ground requires more initial negative camber than I'm willing run on the street. The picture I posted was to show the camber on the loaded rear wheel just before it lost traction. This is with 1.5* negative camber initial and all poly links. It's the best I think my streetable Fiero can do with this suspension design. Yes, I could use a pyrometer to optimize the camber for maximum traction going around a cone at 20 mph, but I wouldn't like driving it the other 99.9% of the time. Hence my interest in an SLA setup.

~Neil

[This message has been edited by sspeedstreet (edited 07-31-2011).]

Will (william.lucke@gmail.com) MSG #84, 07-31-2011 08:59 AM
     
 
quote
Originally posted by sspeedstreet:

My point is that the McPherson strut design is limited by its inability to keep the contact patch intact during jounce and rebound.


BMW and Porsche do just fine with struts. As does Honda since they introduced the RSX. There's nothing inherently wrong with struts, as long as they can be packaged appropriately. They fail, for example, in a car like the GM W-body in which the strut tops are pushed further apart than they are on the Fiero in order to package a larger powertrain. This obviously strictly limits the capacity of the geometry for camber gain.

One of the first/best things you can do for the '88 suspension is ditch the poly and go straight to rod ends in the lateral links. http://www.realfierotech.co...topic.php?f=3&t=2573

After that, try raising the inner pivots of the lateral links. That will raise roll center, move dynamic contract patch loading closer to equal and give the suspension more camber gain.

And run a staggered tire fitment that matches the car's weight distribution.

[This message has been edited by Will (edited 07-31-2011).]

FieroWannaBe (patond@alumni.msoe.edu) MSG #85, 07-31-2011 10:50 AM
      For anyone seriously interested in the discussions going on in this thread, I recommend this book:
http://www.amazon.com/Racin...id=1312122686&sr=8-3

it's not as good as say, Milliken, but Haney does better than others like Adams, or Gillespie, at focusing at the root of the suspension problem, analyzing the history of current solutions that are being used, and has insight from many in-practice professionals. Camber gain, roll center, and wheel rates are all control solutions, but its more important to understand why. Haney here does a good job of using the ground-up engineered approach, starting with what a tire is , how it behaves, and using this behavior, You wont design a Formula Car after reading it, but its not a Textbook, but a book meant to illustrate the point of why tires are the most important factor in a Vehicle's dynamic behavior. I cant claim I'm a technical expert, Ive read a few different authors on the subject, talked about it with several people in the field, they all really try to say the same thing. This book explains it best that I have read. My personal experience is limited to my collegiate design, and what Ive tried to absorb from others.

Establishing a desired tractive force at each corner, under specific operating conditions is the goal, and the suspension allows drivers to do so by controlling specific load, and contanct patch at each wheel.

If someone really would want to go ground up with a fiero, they really need a copy of Milliken's Race Car Vehicle Dynamics, but as for optimizing the FIero towards a specific behavior, Haney is a great resource to begin an analysis.



sspeedstreet (sspeedstreet@verizon.net) MSG #86, 07-31-2011 02:55 PM
     
 
quote
Originally posted by Will:


BMW and Porsche do just fine with struts. As does Honda since they introduced the RSX. There's nothing inherently wrong with struts, as long as they can be packaged appropriately. They fail, for example, in a car like the GM W-body in which the strut tops are pushed further apart than they are on the Fiero in order to package a larger powertrain. This obviously strictly limits the capacity of the geometry for camber gain.


You're killing me here, Will. What does defending struts as used on other vehicles have to do with the shortcomings of the 1988 Fiero design?

 
quote
One of the first/best things you can do for the '88 suspension is ditch the poly and go straight to rod ends in the lateral links. http://www.realfierotech.co...topic.php?f=3&t=2573


I read that some time ago. It did a good job of convincing me that rod ends were too much maintenance for me on my street driven Fiero. Worked for you? Glad to hear it. I ended up making my own Delrin-poly hybrid bushings. There's less than 1/4" of poly for compliance. Very smooth, very quiet and much firmer than stock. Works for me.

 
quote
After that, try raising the inner pivots of the lateral links. That will raise roll center, move dynamic contract patch loading closer to equal and give the suspension more camber gain.


Again, looked at that hard, but this modification is limited by its total lack of adjustability.

 
quote
And run a staggered tire fitment that matches the car's weight distribution.


Of course.



Will (william.lucke@gmail.com) MSG #87, 07-31-2011 03:45 PM
     
 
quote
Originally posted by sspeedstreet:

You're killing me here, Will. What does defending struts as used on other vehicles have to do with the shortcomings of the 1988 Fiero design?

Again, looked at that hard, but this modification is limited by its total lack of adjustability.


The simple act of being a strut suspension doesn't automatically condemn a design to mediocrity. Just like SLA, struts are subject to the packaging constraints of the implementation. In moving from the early rear suspension to the '88 rear suspension, the Fiero engineers actually did pretty much all the right things.

Not sure what you mean by "total lack of adjustability".

[This message has been edited by Will (edited 07-31-2011).]

sspeedstreet (sspeedstreet@verizon.net) MSG #88, 07-31-2011 03:55 PM
     
 
quote
Originally posted by Will:

Not sure what you mean by "total lack of adjustability".



OK. I meant without a torch. Go ahead, pick that apart, I'm done.


Will (william.lucke@gmail.com) MSG #89, 07-31-2011 04:12 PM
      Raising the inner pivots wouldn't result in any less adjustability than the suspension had stock. Since it was already significantly and meaningfully adjustable for camber and toe, I'm not sure what your point is.

[This message has been edited by Will (edited 08-01-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #90, 07-31-2011 10:55 PM
     
 
quote
Originally posted by sspeedstreet:

I have no interest in dedicating my car to track use only . Wide sticky tires, stiffer springs and higher rate sway bars only mask an inherently poor suspension design. Reducing body roll by design would be my goal. Then the spring rate in the rear could be reduced to make the car stick better in wet or uneven road surfaces i.e., The Real World.


From what I've read so far, body roll, by itself isn't that bad, as long as the suspension geometry compensates for it. That's why SLA's have unequal A-arms, so that the tire contact patch remains firmly on the ground, even if the body of the car leans.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #91, 07-31-2011 11:27 PM
      If you can come up with struts that have better geometry than GM's design 30 years ago, then it's one solution to the problem. We can come up with multiple designs, SLA's, struts, multi link, trailing arm, etc. Let's see which one works best. The only one I draw a hard line on is live axles. In the words of Top Gear, that design belongs on lorry's.
Actually, let me ad swing arm to that as well.


bse53 MSG #92, 08-03-2011 01:29 PM
     
 
quote
Originally posted by Black Lotus:

Awhile back I made some measurements of the front and rear suspension pivot points on my '88 for a suspension program that I have.
The front roll center was a little bit HIGHER than the rear roll center. (WTF!) By eyeballing where the masses were in the car, it suggested to me that the roll center axis was out of whack with the mass axis of the car. In other words, this means the the rear overturning rolling moment was much higher than the front and explained the need for the rather large stock anti-roll bar in the back of the Fiero.
Not that this is entirely bad, as it might help the car pass whatever dynamic steering quality tests that the car had to go thru to pass GM steering and stability tests (maybe).
This would explain the feeling that the back end of the car would flop over a bit, even with Koni shocks, which was a real party killer to me because I wanted to put a big 'ol Chevy V8 in it. A big V8 would have made the car scary at the limit, or when recovering from a slide.
The only solution I could see was to put a LOT lighter engine in the back--or lower the existing package-- and raise the rear roll center.
(I would have used this opportunity to remove more weight from the front to keep the weight distribution the same, as that is just fine.)
However, raising the rear roll center puts more lateral load onto the outside rear tire in a corner and makes the car fundamentally more prone to oversteer.
Reducing or eliminating the the rear bar to compensate for the raised rear roll center aggravates the lack of rear suspension travel and would make the rear end more prone to hitting the bumpstops.
What a mess!
At this point, the EASIEST thing to do, because I am lazy, was to put all-season tires on it and and buy a different car for serious driving.





Some of the design problems can't be solved with improved geometry, such as CG height.
I want to lower the car to lower the CG, and create issues with camber changes-- although some of that can be fixed with changed the mounting points of the lower control arms.

I took my C4 vette to the last autocross, since the Fiero is broken, and I had forgotten how much fun that car is. You can throw the car around the course with confidence and the results are predictable. The C4 CG is 15"-- while, according to the drawings by Bloozberry, the Fiero CG is 19.4". The 80's MR2 CG is about the same-- 19". That is going to be tough to change.

The Corvette has issues, such as chassis flex and is heavy for it's power by today's standards.


fieroguru MSG #93, 08-03-2011 06:40 PM
      If you wanted to improve the 88 rear suspension setup, just raise the whole cradle 1" while lowering the engine relative to the cradle about the same amount. It would give you better camber gain and anti-squat and since the engine/transmission elevation remains about the same, the CG should be largely unchanged.

A 2nd cradle sleeve could be welded to the cradle, or the front tabs on the chassis drilled for the 2nd set of holes. The rear of the cradle would need to be sectioned, but the rear uprights are vertical so that makes if pretty simple. To lower the drivetrain you can just section the 3 mounts.



Will (william.lucke@gmail.com) MSG #94, 08-04-2011 02:14 AM
     
 
quote
Originally posted by fieroguru:

If you wanted to improve the 88 rear suspension setup, just raise the whole cradle 1" while lowering the engine relative to the cradle about the same amount. It would give you better camber gain and anti-squat and since the engine/transmission elevation remains about the same, the CG should be largely unchanged.

A 2nd cradle sleeve could be welded to the cradle, or the front tabs on the chassis drilled for the 2nd set of holes. The rear of the cradle would need to be sectioned, but the rear uprights are vertical so that makes if pretty simple. To lower the drivetrain you can just section the 3 mounts.


Except that you can't really do that because the left inner CV joint is essentially right on top of the left inner toe link pivot.

You have to move the toe link inner pivots forward in order to move them up. If you do that, you might as well leave the cradle where it is and weld on the new toe and lateral link mounts.

[This message has been edited by Will (edited 08-04-2011).]

bse53 MSG #95, 08-04-2011 04:49 PM
      Imitation is the sincerest form of flattery.

Here's some views of suspensions from 19 different vehicles. Might give some ideas.

http://blogs.insideline.com...pension-walkarounds/


ccfiero350 (chuckcamp@gmail.com) MSG #96, 08-04-2011 05:13 PM
      I'm groovin on the hyperstrut concept. I'm thinking I can incorporate that link in the strut ear somehow. Fuel for thought. Thanks bse53!




fieroguru MSG #97, 08-04-2011 06:20 PM
     
 
quote
Originally posted by Will:


Except that you can't really do that because the left inner CV joint is essentially right on top of the left inner toe link pivot.

You have to move the toe link inner pivots forward in order to move them up. If you do that, you might as well leave the cradle where it is and weld on the new toe and lateral link mounts.



The last stock 88 2.8 drivetrain I measured had the crankshaft center-line 8 13/16" from the bottom of the cradle with 172K miles on it with worn out factory mounts. The stock height with some good condition mounts is around 9 to 9 1/4". On pretty much every swap I do the drivetrain is lowered on the cradle to get the crankshaft centerline in the 8 to 8 3/8" range... I have done this for SBC, 4.3, 4.9 and 3800SC swaps (all on 88 cradles) with manual transmissions and never have had any interference issues between the transmission/tripod and the lateral link mount boxes.

So there is indeed room to lower the stock drivertain on an 88 cradle to allow the rear cradle to be raised.




Will (william.lucke@gmail.com) MSG #98, 08-04-2011 08:45 PM
      Have you looked at how much clearance there is vs. the relocation that would be required to achieve a worthwhie effect?

[This message has been edited by Will (edited 08-04-2011).]

Will (william.lucke@gmail.com) MSG #99, 08-04-2011 08:46 PM
     
 
quote
Originally posted by ccfiero350:

I'm groovin on the hyperstrut concept. I'm thinking I can incorporate that link in the strut ear somehow. Fuel for thought. Thanks bse53!



Pointless because the rear doesn't steer.


wftb (danjesso@bmts.com) MSG #100, 08-04-2011 10:47 PM
      the two ball joints seem to mimic an unequal A arm setup .i really think this is ingenious .no way i could ever duplicate this setup , and i find it hard to believe cash strapped gm developed this all by them selves . the 911 is struts all around and it out handles pretty much anything , do they have a similar setup ?

[This message has been edited by wftb (edited 10-29-2011).]

bse53 MSG #101, 08-04-2011 11:39 PM
      Here's the effect of raising the inboard mounting points of the lower control arms. I think. I think the previous owner raised them. Right now the cradle ride height is 4" on 15" slicks with a 22.9" diameter.

This is probably lowered beyond optimum.

The simplest way to lower the car is use shorter tires.






ccfiero350 (chuckcamp@gmail.com) MSG #102, 08-05-2011 12:01 AM
      Looks like they were raised about an inch. It does help the camber gain in your lowered car. Have you tried any other ride heights since you got the car?



bse53 MSG #103, 08-05-2011 12:32 AM
      I've lowered the car about 2". The issue at the front with the car this low is bottoming the shocks. I think a simple solution will be to cut the upper mount and add a 2" extension.

I understand this thread is about an ideal suspension or at least as idealized as possible.

I'm mostly interested in tweaking the existing design to it's maximum potential. The previous owner was quite fast with the car as it is. I'd like to make it quicker, if possible.

Most of you are looking for a good handling street car.

I'm looking for the best handling track car (although the setup for autocross and road racing are not necessarily the same). Finding the balance is the key.

I do intend on building a street rod Fiero down the road using either a 4.9 or 3.8.


bse53 MSG #104, 08-05-2011 12:38 AM
      I certainly don't want to hijack this thread.

What I hope to gain out of this is an understanding of the inherent handling flaws that are prompting the desire to redesign the suspension. What doesn't it do that it could do with a better design?

What are the specific design goals?

I will probably re-read the thread when I have some extra time. Much of my question may already be answered.

Brian


ccfiero350 (chuckcamp@gmail.com) MSG #105, 08-05-2011 12:48 AM
      I'm in the track car category myself. I've had the same front issue. Ended up doing about the same thing, but went to taller spindles at the same time. On the rear, doing about the same but designed a new knuckle to lower the links and use a bigger bearing. I can run 315's now.



fieroguru MSG #106, 08-05-2011 08:19 AM
     
 
quote
Originally posted by Will:

Have you looked at how much clearance there is vs. the relocation that would be required to achieve a worthwhie effect?



Nope. Mostly because chassis ride height, spring rates, swaybars, tire side wall deflection, etc. all come into play when you look at the current state and compare it to the modified state. For favorable camber curves on compression and extension, the inboard lateral link pivots need to be higher than the outboard ones at ride height. How much higher they should be really depends on the amount of suspension travel, body roll and tire defection your setup will have.


fieroguru MSG #107, 08-05-2011 08:23 AM
     
 
quote
Originally posted by bse53:
The issue at the front with the car this low is bottoming the shocks. I think a simple solution will be to cut the upper mount and add a 2" extension.



Another option is to use longer bolts and spacers between the lower shock mounting shaft and the bottom side of the lower a-arms.


Will (william.lucke@gmail.com) MSG #108, 08-05-2011 11:33 AM
     
 
quote
Originally posted by fieroguru:

Nope. Mostly because chassis ride height, spring rates, swaybars, tire side wall deflection, etc. all come into play when you look at the current state and compare it to the modified state. For favorable camber curves on compression and extension, the inboard lateral link pivots need to be higher than the outboard ones at ride height. How much higher they should be really depends on the amount of suspension travel, body roll and tire defection your setup will have.


The springs, bars and dampers depend on the suspension and tires, not the other way around. The ideal suspension has one degree of camber gain for one degree of body roll. Assessing where modified geometry is relative to the ideal is not a hand waving argument citing complexity in dependent processes.

The big gain for the Fiero is really the centroid axis inclination vs. roll axis inclination. When the rear roll center is raised, the roll axis inclination more closely matches the centroid axis inclination. This means that the contact pressure on the outboard tires in a corner grows at the same rate per lateral g front and rear. If the static contact pressure is matched front and rear and the suspension acts to grow the outboard contact pressures in the same way front and rear, then the car will remain neutral.

That assumes similar camber performance front/rear, springs/bars/dampers chosen intelligently, etc.


bse53 MSG #109, 08-06-2011 11:22 AM
     
 
quote
Originally posted by Will:


The springs, bars and dampers depend on the suspension and tires, not the other way around. The ideal suspension has one degree of camber gain for one degree of body roll. Assessing where modified geometry is relative to the ideal is not a hand waving argument citing complexity in dependent processes.

The big gain for the Fiero is really the centroid axis inclination vs. roll axis inclination. When the rear roll center is raised, the roll axis inclination more closely matches the centroid axis inclination. This means that the contact pressure on the outboard tires in a corner grows at the same rate per lateral g front and rear. If the static contact pressure is matched front and rear and the suspension acts to grow the outboard contact pressures in the same way front and rear, then the car will remain neutral.

That assumes similar camber performance front/rear, springs/bars/dampers chosen intelligently, etc.



I think I would like to lower the CG and move it closer to the roll center axis. The CG is high on the car because the car was never designed as a sports car, but a sporty car. If the Fiero CG is 19", compare that to the Porsche 911, it's CG is 15". My question is how can I do that. Lowering the cradle and raising the inboard mounting points of the lower control arm/toe arm is a start. I can now get as much static camber as I want.

I think I can balance the car with springs and dampers. Bars not so much. I want to control dive because the front suspension has such limited travel.

Where is my thinking going wrong?


sspeedstreet (sspeedstreet@verizon.net) MSG #110, 08-06-2011 12:48 PM
      I've considered lowering the engine/trans also. I have a spare cradle I was modifying with different engine/trans mounts (and perhaps SLA upper mounts) anyway, so this would be the time to do it. I've also looked at weight at the top of the engine compartment. I've moved the battery to the front and the wing is the next to go. I've got the materials for a carbon fiber lightweight deck lid but haven't had the time to start on the mold. All that should make a difference in the rear CG.

Unfortunately, there's the 3.4 DOHC cams up there. Ever pick up a cam carrier off one of those? It's ridiculous. Wonder if I could get them gun drilled?

~Neil

BTW, it's going to be hard to match a Porsche rear CG when it has a flat 6 motor in it.

[This message has been edited by sspeedstreet (edited 08-06-2011).]

Will (william.lucke@gmail.com) MSG #111, 08-06-2011 04:55 PM
      Porsches have horizontally opposed engines and a lot of them have dry sump lubrication systems, which allow the engine to really sit low in the chassis.

The Corvette mentioned above may have a lower CG than the Fiero, but it's also 600# heavier. If you bolt 600# of lead ballast into the floorboards of a Fiero, the CG will be lower, but you really don't want to do that. There really isn't much room to drop the Fiero CG without doing something extreme like going to a dry sump sysem and lowering the engine while rotating the transmission.

As mentioned above, there's only so much room to raise the inner pivot of the left toe link before it runs into the left inner CV joint. There's more room to raise it if you move it forward about an inch.
I would go for raising the pivots more than lowering the cradle. If you raise the pivots an inch and lower the cradle an inch, you haven't done anything to improve your geometry. If you've lowered the car with shorter springs than stock, you've already compromised the geometry relative to stock, which wasn't great to begin with.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #112, 08-09-2011 01:17 AM
     
 
quote
Originally posted by bse53:

Imitation is the sincerest form of flattery.

Here's some views of suspensions from 19 different vehicles. Might give some ideas.

http://blogs.insideline.com...pension-walkarounds/


Nice. What do you guys think?


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #113, 08-09-2011 01:20 AM
     
 
quote
Originally posted by bse53:

I certainly don't want to hijack this thread.

What I hope to gain out of this is an understanding of the inherent handling flaws that are prompting the desire to redesign the suspension. What doesn't it do that it could do with a better design?

What are the specific design goals?

I will probably re-read the thread when I have some extra time. Much of my question may already be answered.

Brian


That was the goal of this thread, unfortunately it has since been taken off to too many tangents.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #114, 08-09-2011 01:17 PM
      Nice thread.

bse53 MSG #115, 08-10-2011 11:41 AM
     
 
quote
Originally posted by Will:

Porsches have horizontally opposed engines and a lot of them have dry sump lubrication systems, which allow the engine to really sit low in the chassis.

The Corvette mentioned above may have a lower CG than the Fiero, but it's also 600# heavier. If you bolt 600# of lead ballast into the floorboards of a Fiero, the CG will be lower, but you really don't want to do that. There really isn't much room to drop the Fiero CG without doing something extreme like going to a dry sump sysem and lowering the engine while rotating the transmission.

As mentioned above, there's only so much room to raise the inner pivot of the left toe link before it runs into the left inner CV joint. There's more room to raise it if you move it forward about an inch.
I would go for raising the pivots more than lowering the cradle. If you raise the pivots an inch and lower the cradle an inch, you haven't done anything to improve your geometry. If you've lowered the car with shorter springs than stock, you've already compromised the geometry relative to stock, which wasn't great to begin with.


I was merely pointing out some of the obstacles in making the Fiero a true sports car.
Assume the C4 Corvette is 3300 lbs and CG is 15" and track is 59". Lateral weight transfer at 1 g is 838 lbs.
Assume Fiero is 2700 lbs and CG is 19" and track is 59". Lateral weight transfer at 1 g is 869 lbs.

Take 100 lbs off the car and you've equalized the weight transfer (assuming the 100 lbs doesn't come low on the car and actually raise the CG in the process).

Getting the CG lower will make a big difference. Any suspension design should include this consideration. Keeping unsprung weight to a minimum should be a consideration. Any design shouldn't add weight.

All modern sports cars use aluminum extensively in the suspension elements. Corvette uses magnesium to help balance.

Bumpsteer is not as big an issue, even in a pre-87. This design by Held looks effective.


Another important element that I believe is a weak link are shocks. The Fiero has a limited choice of dampers.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #116, 08-10-2011 06:02 PM
      This thread is starting to read like we should just install a flat boxer motor with a dry sump to keep the CG low and all problems will be fixed.

This images is larger than 153600 bytes. Click to view.

So nobody things the geometry of the suspension could be improved with the engine sitting where it does now?


bse53 MSG #117, 08-10-2011 06:24 PM
     
 
quote
Originally posted by Austrian Import:

This thread is starting to read like we should just install a flat boxer motor with a dry sump to keep the CG low and all problems will be fixed.

This images is larger than 153600 bytes. Click to view.

So nobody things the geometry of the suspension could be improved with the engine sitting where it does now?


The assumption I made as to CG height was based on a drawing on this thread. That was based on a ride height of 6.2". Raising the inboard mounting points of the lower control arm/toe rods allows the rear to be lowered a couple of inches without too much affect on geometry. Add the suggestion of lowering the engine in the cradle and you've lowered the engine and CG even more.

If a person is swapping engines, what the engine does to CG should be a consideration for a track car, IMO. I could be wrong. The Fiero I'm messing with has the 4.9l and is producing as much power as it probably can without adding boost. It's relatively light in comparison to the 2.8, but even there aluminum block/cast heads puts the weight up high. The all aluminum LS engines might be a better choice, or what CCfiero350 is doing with the 2.2 ecotec might be the wave of the future for lightweight power.

I'm just suggesting that weight is part of the equation of making a car handle.


Will (william.lucke@gmail.com) MSG #118, 08-10-2011 07:52 PM
      Weight absolutely is. Lightness is the best thing you can add to a car to make it handle. A tire with less weight on it can generate more grip. In addition, if you go from an iron 2.8 to an aluminum 4 cylinder, you can run wider tires in front.

Assuming you're running the widest tires you can in the rear and a proportional tire in front, then you'd end up with something like 225 front/275 rear or 205 front/255 rear with 45/55 weight distribution.

If you can bump that just a couple of percent to 47.5/52.5, then you can widen the front tires from 0.8x the rear to 0.9x the rear. That means 245 front/275 rear and 235 front/255 rear.

Less weight AND you get to put more rubber on the road.

[This message has been edited by Will (edited 08-10-2011).]

sspeedstreet (sspeedstreet@verizon.net) MSG #119, 08-10-2011 08:35 PM
     
 
quote
Originally posted by Will:

A tire with less weight on it can generate more grip.


Really? Then why do F1 cars look like this?



Hint: Downforce = more grip.


bse53 MSG #120, 08-11-2011 11:29 AM
      Aereodynamic downforce is our friend. Unfortunately most autocross class rules don’t allow areo and the amount of area needed to apply any significant amount of downforce at autocross speeds is pretty large.



Downforce is free weight, since it doesn’t affect lateral weight transfer, which is what we were talking about.

There are three ways to reduce lateral weight transfer- lower the CG, reduce weight or increase track width. So for our Fiero we should optimize each of these and then improve the suspension geometry to keep our tires at maximum contact.

We can lower the CG a couple of inches fairly easily, we can lose a few hundred pounds by taking off all the comfort amenities and we can increase track width with wide wheels—since the design of the car forces the wheels outside the car as we increase the width.

On my car, the maximum backspace I can fit is about 5.5”, so a 10” wheel is going to stick outside the stock fenders slightly. Simple solution—widebody. A 10” wheels also allows the 275 size tire. I’m referring to 15” wheels.

So, assume a 60” track and 1g of cornering. Our 2700 lb car at 19” CG will generate 855 lbs of lateral weight transfer. Lighten the car to 2500 lbs and we’ve reduced the WT to 791 lbs.

But let’s lower the CG 2”. Now our 2700 lb car will generate 765 lbs of WT. Lighten the car to 2500 lbs and we’ve lower the WT to 708 lbs.

Pretty obvious we want as light and low a car as possible. If we could lower the car to 0” CG, there would be no weight transfer and our cornering ability would be the limits of the tire. Remember as we transfer weight, we’re adding weight to the outside tires. If the Force at which tires slide is the coefficient (expressed in g’s) times weight and that Force is a function of the tire, as we lower the weight on the tire we increase the g’s we can generate, which translates to speed around a corner up to the stiction of the tire.

Assume a 100' radius corner. At 1g we'll be traveling 38.6 mph. Increase that to 1.25 g and we've increased our speed to just over 43 mph.

Here’s a very good resource on handling by Brian Beckman:

http://phors.locost7.info/contents.htm

Hope I haven't stated the obvious.



Will (william.lucke@gmail.com) MSG #121, 08-11-2011 06:38 PM
     
 
quote
Originally posted by sspeedstreet:


Really? Then why do F1 cars look like this?



Hint: Downforce = more grip.


Weight is not the same as downforce.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #122, 08-11-2011 08:28 PM
      F1 cars are a whole different animal. For starters, I don't think it's feasible for us to use suspension arms as long as they are on F1 cars. Secondly F1 cars actually have a horrible coefficient of drag. (IIRC above 0.45) For F1 cars it doesn't matter though because they make up for it with ungodly amounts of horsepower and grip they can carry through corners.

sspeedstreet (sspeedstreet@verizon.net) MSG #123, 08-11-2011 08:43 PM
     
 
quote
Originally posted by Will:


Weight is not the same as downforce.


Downward force on the contact patch, be it aerodynamic or vehicle mass, is going to increase the tire's adhesion to the road surface. Where mass becomes the enemy is anytime you try to accelerate or decelerate it. In a corner you are changing the direction of the mass of the vehicle, resulting in a lateral force. The more mass or the tighter the turn, the more lateral force is generated until it overcomes the adhesion of the tires.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #124, 08-12-2011 02:13 AM
     
 
quote
Originally posted by Austrian Import:

This thread is starting to read like we should just install a flat boxer motor with a dry sump to keep the CG low and all problems will be fixed.

This images is larger than 153600 bytes. Click to view.

So nobody things the geometry of the suspension could be improved with the engine sitting where it does now?


PM sent. Not sure if you got it?
My answere to your questions is in the PM.



bse53 MSG #125, 08-12-2011 09:27 AM
      Here's a good answer to the question of weight and downforce.

"Difference Between Weight and Downforce"

"You may be wondering why, if aerodynamic downforce can increase cornering speed, does a lighter car corner faster? Why is vertical load provided by aerodynamics different than vertical load provided by weight?..."

http://racingarticles.com/article_racing-3.html


Will (william.lucke@gmail.com) MSG #126, 08-12-2011 10:41 AM
     
 
quote
Originally posted by sspeedstreet:

Downward force on the contact patch, be it aerodynamic or vehicle mass, is going to increase the tire's adhesion to the road surface. Where mass becomes the enemy is anytime you try to accelerate or decelerate it. In a corner you are changing the direction of the mass of the vehicle, resulting in a lateral force. The more mass or the tighter the turn, the more lateral force is generated until it overcomes the adhesion of the tires.


Weight is the result of mass. Weight is not the same as downforce.

And the point I was making is that the plot of normal force vs. maximum lateral force of a tire has the steepest slope at lowest normal force. The less weight there is on a tire, the higher the lateral g it can generate.

Is anything else I've said you'd like to take out of context to argue about?


Will (william.lucke@gmail.com) MSG #127, 08-12-2011 11:51 AM
     
 
quote
Originally posted by Austrian Import:

So nobody things the geometry of the suspension could be improved with the engine sitting where it does now?


Of course it can.

Gordon Murray said "The automotive problem is fundamentally one of packaging".
Once you come up with a design that does what you want without any of the required components occupying the same space, the rest is just a matter of fabrication.


Jncomutt (jncomutt@hotmail.com) MSG #128, 08-12-2011 07:38 PM
      I wish that guy Hank from PA with the 383 fiero was still around. He completely redesigned his front and rear suspension. It was pretty trick from what I can remember from like 10 years ago, or however long it was.

ccfiero350 (chuckcamp@gmail.com) MSG #129, 08-12-2011 08:35 PM
     
 
quote
Originally posted by Will:


And the point I was making is that the plot of normal force vs. maximum lateral force of a tire has the steepest slope at lowest normal force. The less weight there is on a tire, the higher the lateral g it can generate.

Is anything else I've said you'd like to take out of context to argue about?


So this being said, my tires with the most grip will be on unweighted side of the car as I make a turn?



wftb (danjesso@bmts.com) MSG #130, 08-12-2011 09:15 PM
      in answer to why Formula one tires look like they do :they are forced to use spec tires by the rules of F1 .they are not the tires they would be using if they could run whatever they wanted to .

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #131, 08-12-2011 09:51 PM
     
 
quote
Originally posted by Jncomutt:

I wish that guy Hank from PA with the 383 fiero was still around. He completely redesigned his front and rear suspension. It was pretty trick from what I can remember from like 10 years ago, or however long it was.


Are there any pictures of that in existance? At least that may be interesting to look at.


pmbrunelle (pmbrunelle@gmail.com) MSG #132, 08-12-2011 11:23 PM
     
 
quote
Originally posted by ccfiero350:
So this being said, my tires with the most grip will be on unweighted side of the car as I make a turn?


"grip" is a vague term.

Will was referring to grip as available lateral force as a function of normal force (well, its derivative actually).

You're referring to absolute lateral force.

Don't argue over vague terms. It's like "all-natural" on food products. According to the FDA, it doesn't mean anything.


Will (william.lucke@gmail.com) MSG #133, 08-13-2011 12:11 PM
     
 
quote
Originally posted by ccfiero350:

So this being said, my tires with the most grip will be on unweighted side of the car as I make a turn?



Grip is the ratio of maximum lateral force to normal force (textbook definition).
If you have 1000# normal force on your outside tire and 500# on your inside tire, your outside tire might have 0.9 grip, while your inside tire might have 1.1 grip.
That means the outside tire can generate 900# of lateral force and the inside can generate 550.
The total lateral force you have available to turn that end of the car is 1450#.
Since that end of the car weighs 1500#, it can corner at 0.96g (= 1450/1500).

If you add 4,000# of aerodynamic force into the equation, equally distributed, then you'd have 3000# on the outside tire and 2500 on the inside tire.
That might be a grip of 0.70 on the outside and 0.75 on the inside.
Which would give 3975# of lateral force and a cornering acceleration of 2.65g (=3975/1500).

All numbers are pulled directly out of my @$$.

[This message has been edited by Will (edited 08-13-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #134, 08-25-2011 11:45 PM
      I decided to post on a engineering forum, to see if we could gain more expert advice about suspension designs:
http://www.eng-tips.com/vie...fm?qid=305476&page=1


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #135, 08-25-2011 11:58 PM
      Great suspension article: http://www.rqriley.com/suspensn.htm

Will (william.lucke@gmail.com) MSG #136, 08-26-2011 10:06 AM
     
 
quote
Originally posted by Austrian Import:

I decided to post on a engineering forum, to see if we could gain more expert advice about suspension designs:
http://www.eng-tips.com/vie...fm?qid=305476&page=1


You're likely to get very different things than you bargained for, posting there...


Bloozberry MSG #137, 08-26-2011 12:04 PM
      Update: I'm in the midst of drafting up electronic drawings for the '88 front suspension, similar to the rears I've posted. Once complete, I'll post them here. This should enable a more comprehensive analysis of the effects of various changes.

Rickady88GT (rjkmfam@sbcglobal.net) MSG #138, 08-26-2011 03:55 PM
     
 
quote
Originally posted by Bloozberry:

Update: I'm in the midst of drafting up electronic drawings for the '88 front suspension, similar to the rears I've posted. Once complete, I'll post them here. This should enable a more comprehensive analysis of the effects of various changes.



Sorry if you have said alreardy but I have to ask anyway.
Do you get your info from a suspension system out of your car or from technical data?



Austrian Import (maximilian_ledworowski@csumb.edu) MSG #139, 08-26-2011 06:08 PM
     
 
quote
Originally posted by Will:
You're likely to get very different things than you bargained for, posting there...


Why is that? I have to say I'm not familiar with that forum. (the data may be too technical, but it's worth trying)


ccfiero350 (chuckcamp@gmail.com) MSG #140, 08-26-2011 08:55 PM
      My guess maybe is that Will has an aversion to engineers.



Bloozberry MSG #141, 08-26-2011 10:22 PM
     
 
quote
Originally posted by Rickady88GT:

Do you get your info from a suspension system out of your car or from technical data?


For the rear, I used a combination of:

1. some of the cradle, ride height, and alignment dimensions from the service manual;
2. some additional frame alignment data from a tech service provided to collision centers;
3. the car's center of gravity height from Road & Track; and
4. the rest was by spending 300 hours measuring and drawing the parts from my project car.

I'm using the same approach to draw the front suspension, hopefully it will take less time.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #142, 08-27-2011 06:40 PM
     
 
quote
Originally posted by Bloozberry:


For the rear, I used a combination of:

1. some of the cradle, ride height, and alignment dimensions from the service manual;
2. some additional frame alignment data from a tech service provided to collision centers;
3. the car's center of gravity height from Road & Track; and
4. the rest was by spending 300 hours measuring and drawing the parts from my project car.

I'm using the same approach to draw the front suspension, hopefully it will take less time.



WOW cool. thanks.



PerKr (per_kristoffersson1@hotmail.com) MSG #143, 08-27-2011 07:52 PM
     
 
quote
Originally posted by Austrian Import:


Why is that? I have to say I'm not familiar with that forum. (the data may be too technical, but it's worth trying)


they're engineers, so they'll ask you what you are trying to achieve and what you think is wrong with the current design. you'll get a general description of the direction you might want to look in, but asking them to give you a detailed answer without giving a detailed description of the current situation... they spend hours and days designing a suspension in a given space, then send it to lab and analysis departments, then tweaking and testing until the desired test results are achieved. you're asking them to take years and years of education and experience and condense it all into a post saying "use these values, see this sketch for reference".


Robert Reif (reif@earthlink.net) MSG #144, 08-27-2011 09:55 PM
      Has anyone looked into transplanting some or all of the Pontiac Solstice suspension into a Fiero? I would think Pontiac engineers learned something since the Fireo and It would be one way of utilizing that knowledge and modernizing the Fiero.

Here are some links:

http://www.solsticeforum.co...wphoto.php?photo=157
http://www.solsticeforum.co...wphoto.php?photo=158


Will (william.lucke@gmail.com) MSG #145, 08-28-2011 12:01 PM
     
 
quote
Originally posted by ccfiero350:

My guess maybe is that Will has an aversion to engineers.



The languages used by professional engineers and hobbyist engineers is very different. Do you have any idea what the fundamental frequency of the Fiero suspension is? Of the body tub? Torsional stiffness?


ricreatr MSG #146, 08-29-2011 01:54 AM
      hi guys it's been a while.

this is some GREAT info and discussion!

the buick hyperstrut - http://blogs.insideline.com...mb-717x478-92946.jpg
i think the strut idea is useless for the rear, but the KNUCKLE is very interesting, it could be used for a sla in the rear. the ball joints are moved closer to the rotor than others we had tried to check out several years ago. the scrub radius looks promising.

the compact car articles seemed to downplay drop knuckles in favor of springs. ? seems like knuckles would solve the geometry changes they were facing. the shot of the custom 88 rear knuckle was great. similar to a drop knuckle in that it moved the suspension points down, great cause there really is little room to move the inboard joints up.

i had the same problem with heim joints several years back, they wore out very fast. i used dust shields, they just fell apart and were useless. i even drilled them out for a "needle" grease gun fitting. helped a little. was it the "Speedway Motors" parts?

cant wait to see those 88 front drawings!


ccfiero350 (chuckcamp@gmail.com) MSG #147, 08-29-2011 12:17 PM
     
 
quote
Originally posted by Will:


The languages used by professional engineers and hobbyist engineers is very different. Do you have any idea what the fundamental frequency of the Fiero suspension is? Of the body tub? Torsional stiffness?


Its funny you should say this, I worked for NASA a few years back with one of the leading physicist on harmonics and suspensions from Lockheed Martin on the IRED, Isolated Resistive Exercise Device. It's essentially a working platform that's connected to the bulkhead over the view port in Node 1 on the space station. I designed the platform and he designed the iso-links. Our job was to isolate the moments imposed on the space station structure by the working exercise platform in micro-gravity while the astronauts did their physical training.


Here my fat azz on the prototype during mock-up on the air bearing floor in building 9. Sorry for the bad pics, it was scanned in from a trade journal.

It was a lot of fun, even working with the Russians was okay if you could stand their chain smoking.


Will (william.lucke@gmail.com) MSG #148, 08-29-2011 04:36 PM
     
 
quote
Originally posted by Robert Reif:

Has anyone looked into transplanting some or all of the Pontiac Solstice suspension into a Fiero? I would think Pontiac engineers learned something since the Fireo and It would be one way of utilizing that knowledge and modernizing the Fiero.

Here are some links:

http://www.solsticeforum.co...wphoto.php?photo=157
http://www.solsticeforum.co...wphoto.php?photo=158


Gordon Murray said that the automotive problem is fundamentally one of packaging. Think about that for a minute and the answer should become apparent...


ricreatr MSG #149, 08-29-2011 05:05 PM
      hey, anyone in this area looking to contribute to this thread and might like to test on a high falootin alignment rack, . . . pm me.

Robert Reif (reif@earthlink.net) MSG #150, 08-29-2011 06:32 PM
     
 
quote
Originally posted by Will:


Gordon Murray said that the automotive problem is fundamentally one of packaging. Think about that for a minute and the answer should become apparent...


Not really. Anything is possible with enough time and money. My question was has anyone looked into doing this yet.

I don't have a Solstice to take measurements from to see if this is even practical. The main difference is the addition of an upper control arm to replace the strut in the rear. If I had access to the Solstice mounting point locations and component dimensions, I could answer the question myself.


ccfiero350 (chuckcamp@gmail.com) MSG #151, 08-29-2011 11:10 PM
     
 
quote
Originally posted by ricreatr:

hey, anyone in this area looking to contribute to this thread and might like to test on a high falootin alignment rack, . . . pm me.


Do you have access to one of those Shaker racks that simulate road conditions?



Will (william.lucke@gmail.com) MSG #152, 08-30-2011 09:45 AM
     
 
quote
Originally posted by Robert Reif:

Not really. Anything is possible with enough time and money. My question was has anyone looked into doing this yet.

I don't have a Solstice to take measurements from to see if this is even practical. The main difference is the addition of an upper control arm to replace the strut in the rear. If I had access to the Solstice mounting point locations and component dimensions, I could answer the question myself.


Getting components A and B to share the same location in space isn't possible, no matter how much money you have.

The Solstice suspension was designed for the Solstice, with packaging considerations totally different from those of the Fiero. Also, the Solstice is a front engine car, so roll axis inclination, etc. are not likely to be right for a mid/rear car.


bse53 MSG #153, 08-30-2011 09:59 AM
     


Porsche 914 with SBC. Does anything strike you-- like the CG height? Part of this is the benefit of not mounting the engine above the transmission.

Here's the entire build.

http://www.negativereinforc...acing.com/update.htm

Don't sell the Fiero suspension short. The reason it's not competitive has more to do with the lousy power to weight ratio in stock form than the suspension itself (at least the '88). When i get the car sorted out, it will be competitive for fast time of day, up there with the stock Z06's and Elises and various modified cars like the SBC 240Z, Rotary MG Midget, uber-boosted 240 SX and the like.

It may have already been discussed previously, but what characteristics that the car suffers from in stock form are you trying to address?

bump steer?
pro-dive?
pro-squat?
roll center too low in relation to CG?
loss of camber?
???

The C4 Corvette, Honda S2000 and Solstice GXP are in the same autocross class. Currently the top car nationally is the S2000. From what I've seen, it is a hard car to drive fast. Of the top 10 cars at last year's nationals, 8 were Hondas. 5th place was a C4, and 8th was a Solstice.



Robert Reif (reif@earthlink.net) MSG #154, 08-30-2011 07:51 PM
     
 
quote
Originally posted by Will:

The Solstice suspension was designed for the Solstice, with packaging considerations totally different from those of the Fiero. Also, the Solstice is a front engine car, so roll axis inclination, etc. are not likely to be right for a mid/rear car.


Here is a link to someone else asking the same question. http://www.fiero.nl/forum/Forum1/HTML/080944.html

Unfortunately there is no answer.


Will (william.lucke@gmail.com) MSG #155, 08-30-2011 08:32 PM
      Some rudimentary measurements from the parts in his second picture should tell him whether it's even possible to do.



The width of the transverse powertrain that has to fit between the upper control arm mounts really pushes the lower frame rails outward. This pushes the upper control arm inner pivots outward. If you can design a knuckle around this, you may make the whole thing work.

However, if you're dealing with a pre-selected set of geometry, your only option is just to keep pushing it further outboard. My guess, simply from looking at that picture, is that Solstice geometry grafted directly into a Fiero would end up with a hub-to-hub distance maybe 6 inches greater than that of the stock Fiero. If you're building an IMSA kit, that's probably fine. If you want to keep everything under the stock bodywork, that's more difficult.

[This message has been edited by Will (edited 08-30-2011).]

Will (william.lucke@gmail.com) MSG #156, 08-30-2011 08:35 PM
      My opinion is that an SLA package that would work in a Fiero is going to be something more like BMW's E36 rear suspension.

Rickady88GT (rjkmfam@sbcglobal.net) MSG #157, 08-31-2011 04:18 AM
     
 
quote
Originally posted by Will:

Some rudimentary measurements from the parts in his second picture should tell him whether it's even possible to do.



The width of the transverse powertrain that has to fit between the upper control arm mounts really pushes the lower frame rails outward. This pushes the upper control arm inner pivots outward. If you can design a knuckle around this, you may make the whole thing work.

However, if you're dealing with a pre-selected set of geometry, your only option is just to keep pushing it further outboard. My guess, simply from looking at that picture, is that Solstice geometry grafted directly into a Fiero would end up with a hub-to-hub distance maybe 6 inches greater than that of the stock Fiero. If you're building an IMSA kit, that's probably fine. If you want to keep everything under the stock bodywork, that's more difficult.



I have done the best "gestamating" that I can without having a Solstice or Sky to draw from and I do think this will fit in the Fiero. I cant find the measurments of the KAPPA suspension pinnings anywere. I have asked a few people who have one if they could help out with a few measurments and or pictures, but nothing yet. SO if anyone can help out with measurments of the KAPPA suspension geomitry I would VERY much like to have it So the best I can go by are the steering rack and sway bar widths. With them all bolted together and "mocked up" I have come up with some crude measurments. Those mesurments do allow this KAPPA suspension room to fit within the frame/ space. BUT this is a much wider suspension than the Fiero and would need a wide body kit or widened fenders.

If I remember right, the upper A arms do not have a clearance problem with the engine because they are stagered oposite of the lower a arms. the lower a arms are biased to the front of the car and the upper are biased to the rear. So one of the upper a arm mounts will nearly be mounted in the trunk, not next to the engine.
Look close at where the drive shaft would go. Look at the coilover shock offset to the rear of the drive shaft. Then look at the a arms, how the upper wraps around the rear of the coilover shock and the lower A arm front side leg is near the crak pulley. The A arms are not an A, the upper "A" arm has one "leg" that runs directly over the drive shaft and one that runs away from the drive shaft. So the upper A arm needs a mount just over the top of the drive shaft and a mount over the top of the cradle mount bolt kind of in the trunk. The lower A arm is the same but has a mount under the tripot and the other mount some were near the crank pulley. Notice that the upper A arm is shorter than the lower and needs the mounts on the outside of the frame rails in the fender wheels.



The lower A arms look like they can be mounted directly to new mounting points welded on the cradle with little change in width from the stock Fiero pinnings.

[This message has been edited by Rickady88GT (edited 08-31-2011).]

Rickady88GT (rjkmfam@sbcglobal.net) MSG #158, 08-31-2011 04:36 AM
      BTW I have several pics of the front and rear suspension components side by side with the 88Fiero suspension.
This KAPPA suspension is a MUCH better suspension than the 88 Fiero.
The wheel bearings are all exactly the same on all four corners and are HUGE next to the Fiero bearings.
The KAPPA is made to use MUCH larger wheels than the Fiero. 19" x 10" no problem as long as you have WIDE fenders.
The KAPPA suspension is made to have a lower ride height from the factory than the Fiero. So you wont need to lower it and compromize geomitry.
The brakes are 12" from the factory. Massive front rotor and a nonvented disk in the rear.
The aftermarket can get you what ever spring rate you need to weight jack the car.
The shocks are also aftermarket friendly.
So "tuning" the suspension is possible.
I think? the sway bars can be aftermarket as well for further tuning.
It has the new style "ball joint" sway bar links.
Several aftermarket brake upgrades to pick from.
You could get poly if you want.
Faster ratio power steering comes standard with a KAPPA swap.
All this and I have not even mentioned the geomitry changes that could be better than the Fiero. Like adjustable caster in the front AND rear.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #159, 08-31-2011 05:16 AM
     
 
quote
Originally posted by Robert Reif:

Has anyone looked into transplanting some or all of the Pontiac Solstice suspension into a Fiero? I would think Pontiac engineers learned something since the Fireo and It would be one way of utilizing that knowledge and modernizing the Fiero.

Here are some links:

http://www.solsticeforum.co...wphoto.php?photo=157
http://www.solsticeforum.co...wphoto.php?photo=158



Yes, I have. I have the entire suspension steering and brake system from a Solstice- less the master/booster and rear sway bar.
I have "mocked" it up within the rear clip of an 88. It looks VERY doable BUT I do not have the exact measurments I need to say for sure if it will work or not.



Robert Reif (reif@earthlink.net) MSG #160, 09-01-2011 07:38 AM
     
 
quote
Originally posted by Rickady88GT:


Yes, I have. I have the entire suspension steering and brake system from a Solstice- less the master/booster and rear sway bar.
I have "mocked" it up within the rear clip of an 88. It looks VERY doable BUT I do not have the exact measurments I need to say for sure if it will work or not.


I think the proper approach is to do what was suggested in the other thread.

Determine the desired track, ride height and tire size and that will determine the general location of the lower control arm mounting points. This assumes you want a level lower control arm at the desired ride height (which may not be the case). From there you set the desired camber and that will give you an arc for the possible upper control arm mounting points. Then use a suspension geometry program to determine the best location on that arc. You also need to consider anti-squat and bump steer.

Mounting point measurements from the original car are only relevant if the track remains the same. They can also be used as a starting point and as a sanity check.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #161, 09-01-2011 10:51 AM
     
 
quote
Originally posted by Robert Reif:


I think the proper approach is to do what was suggested in the other thread.

Determine the desired track, ride height and tire size and that will determine the general location of the lower control arm mounting points. This assumes you want a level lower control arm at the desired ride height (which may not be the case). From there you set the desired camber and that will give you an arc for the possible upper control arm mounting points. Then use a suspension geometry program to determine the best location on that arc. You also need to consider anti-squat and bump steer.

Mounting point measurements from the original car are only relevant if the track remains the same. They can also be used as a starting point and as a sanity check.



Where could I get a program like that? Free? Online?
The track is set in stone because I am using the stock Solstice sway bars and steering rack. I could then "tune" them if needed by trying diferent sizes. Ride height is also set, lower A arms will be level and in the same basic location as the stock Fiero pinnings.



Will (william.lucke@gmail.com) MSG #162, 09-01-2011 10:56 AM
     
 
quote
Originally posted by Rickady88GT:

Ride height is also set, lower A arms will be level and in the same basic location as the stock Fiero pinnings.


Is there an engineering or design reason that drives you to those choices?


bse53 MSG #163, 09-01-2011 11:33 AM
     
 
quote
Originally posted by Rickady88GT:


Where could I get a program like that? Free? Online?
The track is set in stone because I am using the stock Solstice sway bars and steering rack. I could then "tune" them if needed by trying diferent sizes. Ride height is also set, lower A arms will be level and in the same basic location as the stock Fiero pinnings.


Here are some of the choices:

http://www.eng-tips.com/faqs.cfm?fid=768

My understanding of some of the limitations of the stock Fiero front suspension has to do with rack placement (Ackerman) and camber/caster curve. As far as I can figure out, you can have static negative camber or positive caster, but not both.

"I agree with Greg that the key issue is a rack ahead of wheel center promotes deflection understeer and rack behind wheel center will tend to have deflection oversteer. I would add that a rack behind wheel center does have two advantages 1)often allows a tighter vehicle turn radius by allowing higher maximum steer angles. 2) Allows you to design in the proper Ackermann correction without moving the rack much out of line with the outer tie-rods. If the rack is significantly forward or back of the outer tie-rod joint, steering forces will introduce an undesireable fore-aft force into rack."

http://www.irday.com/html/A.../20080413/10168.html


Rickady88GT (rjkmfam@sbcglobal.net) MSG #164, 09-01-2011 12:18 PM
     
 
quote
Originally posted by Will:


Is there an engineering or design reason that drives you to those choices?



Yes, I dont realy have plans to change the stock geomitry of the KAPPA. So I would just put it all in as close to stock as I can. The ride height of the KAPPA is fine, no need to change. The steering rack determans the track, keeping it all original.
The bearing cariers are MUCH taller than the Fiero allowing for a lower ride height and larger wheels.



ccfiero350 (chuckcamp@gmail.com) MSG #165, 09-01-2011 12:29 PM
     
Here are some side by side images.


They are much taller



Will (william.lucke@gmail.com) MSG #166, 09-01-2011 01:31 PM
     
 
quote
Originally posted by Rickady88GT:

Yes, I dont realy have plans to change the stock geomitry of the KAPPA. So I would just put it all in as close to stock as I can. The ride height of the KAPPA is fine, no need to change. The steering rack determans the track, keeping it all original.
The bearing cariers are MUCH taller than the Fiero allowing for a lower ride height and larger wheels.


A point I tried to make above is that the Kappa geometry as implemented in the Kappa is probably not right for the Fiero due to the difference in engine placement and accompanying difference in centroid axis inclination.

 
quote
Originally posted by Will:

The Solstice suspension was designed for the Solstice, with packaging considerations totally different from those of the Fiero. Also, the Solstice is a front engine car, so roll axis inclination, etc. are not likely to be right for a mid/rear car.

[This message has been edited by Will (edited 09-01-2011).]

Rickady88GT (rjkmfam@sbcglobal.net) MSG #167, 09-01-2011 02:45 PM
     
 
quote
Originally posted by Will:




For an 88, I do think you are right. Other Fieros would most likely be better off with this suspension than a Chevette Citation combo.
What we dont know is how negativly or posativly a KAPPA suspension will affect the 88? Then figure in the negative affects of compromized geomitry from lowering and wheel size and offsets. What is wores for the 88, stock KAPPA suspension wheels and ride height or compromized 88 suspension?
We could make it even more compicated if we try to figure in engine, trans, and body swaps.

Maybe I am not like most on this forum? I would do this swap just to say I have it. Thats it. It looks SSSOOO much better than the stock Fiero stuff and the elimination of shock towers is super trick.

[This message has been edited by Rickady88GT (edited 09-01-2011).]

Bloozberry MSG #168, 09-01-2011 04:18 PM
     
 
quote
Originally posted by Rickady88GT:

What we don't know is how negatively or positively a KAPPA suspension will affect the 88? Then figure in the negative affects of compromized geometry from lowering and wheel size and offsets. What is worse for the 88, stock KAPPA suspension wheels and ride height or compromized 88 suspension?


One of the main reasons I'm drawing out the stock '88 Fiero suspension, is so that these questions may be easier to answer, at least theoretically. The effect of things like lowered ride height and tires on a stock Fiero suspension should be easily analyzed once the main drawings are done. It would be considerably more work though to compare the impact of the Kappa suspension installation since a whole-scale effort to draw out its geometry would be needed. Without going through that effort, I think it would be difficult to know in advance if the net result would be positive or negative, so I can understand why you might be tempted to just go ahead an do it. It's a lot of work and time to analyze suspension geometry.

Here in the Canadian Maritimes, we don't have the luxury of just swapping in something else. We will soon only be able to install OEM approved modifications (fat chance of that with a Fiero!), or failing that, have to prove to a provincially certified mechanical engineer that suspension changes result in equal or improved handling over an OEM design. Without this special one-time approval, the normal garages that perform yearly mandatory mechanical fitness inspections won't even touch your car. (Hence the real reason I'm going through this exercise of drawing out the suspension.)


Will (william.lucke@gmail.com) MSG #169, 09-01-2011 09:29 PM
     
 
quote
Originally posted by Rickady88GT:

For an 88, I do think you are right. Other Fieros would most likely be better off with this suspension than a Chevette Citation combo.
What we dont know is how negativly or posativly a KAPPA suspension will affect the 88? Then figure in the negative affects of compromized geomitry from lowering and wheel size and offsets. What is wores for the 88, stock KAPPA suspension wheels and ride height or compromized 88 suspension?
We could make it even more compicated if we try to figure in engine, trans, and body swaps.

Maybe I am not like most on this forum? I would do this swap just to say I have it. Thats it. It looks SSSOOO much better than the stock Fiero stuff and the elimination of shock towers is super trick.



IOW, there are no design or engineering choices driving you to install the suspension exactly as it is in the Kappa.

In terms of camber performance, the early Fiero rear suspension is "good enough". IE, I can achieve enough static camber that the tire wears evenly when I explore the car's cornering limits. The early rear's deficiencies lie in bump steer and pro-squat. With lower control arms level, the early rear's roll center is likely too low.

The Kappa rear end may have camber performance that allows the Fiero to use less static camber to achieve the same dynamic camber.
When installed with the lower control arms level, the Kappa setup will likely have a low rear roll center. This will NOT be superior to the stock Fiero hardware.
I don't know how much anti-squat the Kappa platform has built-in, but it's probably NOT pro-squat like the Fiero, so that would be an improvement.

HOWEVER... If you change the elevation of the inner pivots of upper and lower control arms relative to the Kappa mounting, you can raise the rear roll center relative to what it would be in the Kappa and make it more appropriate to the Fiero.
You can also configure the side view of the control arm pivots for anti-squat. This would involve raising the forward pivot of the LCA and lowering the rear pivot of the UCA. This is likely to run into problems with clearance to the transmission on the left side and the crank pulley on the right side.
However, if you swap the control arms left for right, you can avoid that. Keep the knuckles on their original sides. The LCA would be "staggered" to the rear and the UCA to the front, opposite of the configuration in the Kappa. This would give you more flexibility in mounting the LCA pivots and setting up the suspension correctly for the Fiero.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #170, 09-01-2011 09:41 PM
      I dont think the upper and lower arm are level. They do have anti-sqat built into the system. I just dont know how much.
Not only that but I also think that the left and right A arm mounts upper and lower are closer at the front than the rear mounts, measured from side to side. BUT I could be wrong?


Will (william.lucke@gmail.com) MSG #171, 09-01-2011 10:51 PM
      That would be something you'd have to measure on a Kappa body.

Rickady88GT (rjkmfam@sbcglobal.net) MSG #172, 09-01-2011 11:05 PM
     
 
quote
Originally posted by Will:

That would be something you'd have to measure on a Kappa body.



Yep, or cut out a front and rear clip and graft them into the Fiero.



Will (william.lucke@gmail.com) MSG #173, 09-01-2011 11:48 PM
      Lol. Ok, whatever.

Rickady88GT (rjkmfam@sbcglobal.net) MSG #174, 09-02-2011 12:37 AM
     
 
quote
Originally posted by Will:

Lol. Ok, whatever.



LOL, I know how that sounds, but it is an option. Just as the front "cradle" or K mmber drops out of the Fiero I would graft in or weld in that same KAPPA structure. Sounds crazy, but I have seen a sell booklet that show cased some after market suspension stuff for the KAPPA and they had a front clip/frame section from a Solstice to display the entire suspension system just like the Fiero system once removed. The plan would be to permenently weld it in place of the Fiero K member.
The rear is a little more work.
The KAPPA's are in the wecking yards ready for me to walk up with a Honda i2000 and a sawzal

http://www.solsticeforum.co...k-tower-brace-53657/

[This message has been edited by Rickady88GT (edited 09-02-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #175, 09-02-2011 12:39 AM
      Rick could you post more side-by-side pictures? Also the rear suspension side by side?

While a stock Solstice suspension may or may not work, at least we're discussing it. That's a step in the right direction. There is obviously not just one solution to the suspension problem. Let's see which versions we can come up with.


Now we could do a solidworks/pro-engineer mockup of a solstice suspension and see how it reacts. Then add the data we know about the Fiero (CG, weight distribution, etc.)

btw.: Thanks to Borders going out of business :sheds tear: books on chassis engineering and Solidworks and other software can be had for cheap. (not to say that there isn't a learning curve, but no time to start like the present.
Dassault Systems (the guys behind Solidworks) Parametric Technology (Creo, which is the new name for Pro/Engineer also do student versions of the software, which are much nearer affordable.
Another solution is looking up a near college that has an engineering program. Who knows, maybe there is a student in search of a semester project. Another avenue are regional distributors of 3D design/CAD software: They often hold free seminars, Q and A sessions, etc. where they try to peddle their products.

[This message has been edited by Austrian Import (edited 09-02-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #176, 09-02-2011 01:08 AM
      Kind of what I had in mind:






This one I thought was interesting, considering how high the upper A-arm is mounted.





Will (william.lucke@gmail.com) MSG #177, 09-02-2011 07:19 AM
     
 
quote
Originally posted by Austrian Import:

Kind of what I had in mind:

http://www.youtube.com/watch?v=T-ZyFtAQe7w

http://www.youtube.com/watch?v=M6cY6ompzvs

This one I thought was interesting, considering how high the upper A-arm is mounted.
http://www.youtube.com/watch?v=b55qpzqKC6Q



Tall knuckle designs give good steering geometry, but poor camber performance.


Will (william.lucke@gmail.com) MSG #178, 09-02-2011 09:46 PM
     
 
quote
Originally posted by Rickady88GT:

LOL, I know how that sounds, but it is an option. Just as the front "cradle" or K mmber drops out of the Fiero I would graft in or weld in that same KAPPA structure.


The "Clip" is the front frame and body forward of the firewall. It is *NOT* the same as the suspension crossmember.

[This message has been edited by Will (edited 09-02-2011).]

Rickady88GT (rjkmfam@sbcglobal.net) MSG #179, 09-03-2011 03:17 AM
     
 
quote
Originally posted by Will:


The "Clip" is the front frame and body forward of the firewall. It is *NOT* the same as the suspension crossmember.



I understand. In short I would think about cutting out the suspension pinnings from the KAPPA and weld them into the Fiero. This would also make a more presice frame/suspension system. The stock Fiero only has one pin to locate the front K member. This pin does not lokate the K member all that close to ideal. The +/- is to much.
Welding in a suspension mount system will help.



Will (william.lucke@gmail.com) MSG #180, 09-03-2011 09:30 AM
      So you understand my reaction

On the early cars, the crossmember is effectively located by the rear LCA pivots which are welded to the body.

The '88's different, but with 8 mounting bolts instead of 4, the hole tolerances in random directions are likely to locate the subframe pretty precisely.

And on the '88's the relative relationships or the pivots are all determined by the subframe anyway, so if the subframe's out a tiny bit relative to the chassis, it doesn't matter. The toe adjustment makes up for it.

[This message has been edited by Will (edited 09-03-2011).]

lateFormula MSG #181, 09-03-2011 09:59 AM
     
 
quote
Originally posted by Austrian Import:

Now we could do a solidworks/pro-engineer mockup of a solstice suspension and see how it reacts. Then add the data we know about the Fiero (CG, weight distribution, etc.)

Another solution is looking up a near college that has an engineering program. Who knows, maybe there is a student in search of a semester project. Another avenue are regional distributors of 3D design/CAD software: They often hold free seminars, Q and A sessions, etc. where they try to peddle their products.


Austrian, I thought you were doing the CAD design??? I am a mechanical designer for a major teir one supplier to the automotive industry. On my work PC I have UG NX4, UG NX7.5, Catia V5 R16, R18, R19, ProE WF4, and SolidWorks 2010. I am proficient in these softwares and use them every day.

But I am not going to volunteer to do this. I highly doubt anyone could provide the data needed to create such a model with any accuracy. Every pivot point of the suspension is an axis, which in order to model correctly, has to have accurate X, Y, Z coordinates. To model up something like this with very simple solids would take a lot of manhours. If you wanted it to look like some of the videos you've posted; where the suspension components have near production geometry, that would require a LOT of manhours at the tube. Then to create a motion simulation, forget it. This would not be a short project, and would require someone with a fair amount of CAD proficiency.

[This message has been edited by lateFormula (edited 09-03-2011).]

bse53 MSG #182, 09-03-2011 11:22 AM
      Doing any design work in 3d modeling software is time consuming.

These folks spent 1500 hours on their aluminum bodied Cobra replica.

http://www.kirkhammotorspor.../book_aoe/aoe_02.pdf

This gives you a flavor of what's involved.

Their copper bodied '40 Ford is a work of art.

http://www.kirkhammotorspor...-cars/copper-40-ford


Robert Reif (reif@earthlink.net) MSG #183, 09-03-2011 11:49 AM
     
 
quote
Originally posted by Rickady88GT:


Where could I get a program like that? Free? Online?
The track is set in stone because I am using the stock Solstice sway bars and steering rack. I could then "tune" them if needed by trying diferent sizes. Ride height is also set, lower A arms will be level and in the same basic location as the stock Fiero pinnings.


When I was actively racing my Fiero in the 90's I use A-ARM Suspension Geometry PRO from Autoware. It was very easy to enter in the 3D coordinates of all the pivot points and it spit out all the curves. It was crude and only did one end of the car but it was cheap and simple to use. It was great for doing what-if changes and looking at the results.

I would be surprised if there isn't much better open source software available today.


bse53 MSG #184, 09-03-2011 12:04 PM
      Totally off topic, but here is the story, of which the suspension design chapter was taken.

"Larry Ellison, CEO of Oracle, commissioned Kirkham Motorsports build the ultimate, cost is no object, roadster. Spanning the 2 1/2 years between idea and completion, this book reveals the secrets of the ultimate car."

Lots of pictures. Incredible workmanship.

http://www.kirkhammotorspor...-billet-chassis-book


sspeedstreet (sspeedstreet@verizon.net) MSG #185, 09-03-2011 12:52 PM
      I came across this on the web:

http://www.racingaspirations.com/?p=286

Bone simple, but it allows you to plug in your known lengths and heights and then play with different UCA lengths and angles.

~Neil


Will (william.lucke@gmail.com) MSG #186, 09-03-2011 05:46 PM
      That looks like it only does one corner of the car at a time...

That's almost useless because it doesn't tell you anything about the car's roll center.


sspeedstreet (sspeedstreet@verizon.net) MSG #187, 09-03-2011 06:06 PM
      Never mind.

[This message has been edited by sspeedstreet (edited 09-03-2011).]

Zac88GT (snarfboot@hotmail.com) MSG #188, 09-03-2011 07:48 PM
      Lotus Suspension Analyzer is a pretty decent software for analyzing the kinematics. If you scour the internet you might be able to find a copy. I was only able to use the shark module so I could only play around with the kinematics. If you can get the the raven module working you can specify bushing and tire stiffness and it will do a compliant analysis and can simulate performance characteristics of particular maneuvers.

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #189, 09-05-2011 08:13 PM
     
 
quote
Originally posted by lateFormula:


Austrian, I thought you were doing the CAD design??? I am a mechanical designer for a major teir one supplier to the automotive industry. On my work PC I have UG NX4, UG NX7.5, Catia V5 R16, R18, R19, ProE WF4, and SolidWorks 2010. I am proficient in these softwares and use them every day.

But I am not going to volunteer to do this. I highly doubt anyone could provide the data needed to create such a model with any accuracy. Every pivot point of the suspension is an axis, which in order to model correctly, has to have accurate X, Y, Z coordinates. To model up something like this with very simple solids would take a lot of manhours. If you wanted it to look like some of the videos you've posted; where the suspension components have near production geometry, that would require a LOT of manhours at the tube. Then to create a motion simulation, forget it. This would not be a short project, and would require someone with a fair amount of CAD proficiency.



I never considered it to be a short project. I'm not that naiive. It's part of the reason why I wanted this to be a collaborative open source project. (I've worked a bunch of projects where people donated their time towards a common good. How do you think other big projects get done i.e.: Firefox anyone? )
So it's not just one person investing a lot of manhours into this. A lot of the structural measurements are already in this thread, the rest can be taken from a Factory service manual, and/or a bodyshop manual.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #190, 09-05-2011 08:15 PM
     
 
quote
Originally posted by Zac88GT:

Lotus Suspension Analyzer is a pretty decent software for analyzing the kinematics. If you scour the internet you might be able to find a copy. I was only able to use the shark module so I could only play around with the kinematics. If you can get the the raven module working you can specify bushing and tire stiffness and it will do a compliant analysis and can simulate performance characteristics of particular maneuvers.


This is cool. I gotta look into that.


Bloozberry MSG #191, 09-05-2011 10:48 PM
     
 
quote
Originally posted by Austrian Import:
A lot of the structural measurements are already in this thread, the rest can be taken from a Factory service manual, and/or a bodyshop manual.


Not so. Only the structural measurements for the rear end can be found in this thread so far. I can guarantee you that the rest (ie the front end dimensions) can't be found in the service manual or bodyshop manuals. They only give the measurements for where the front cross member attaches to the rest of the frame, nothing about the cross member, the control arms, knuckles or steering rack though.

Within two or three days I'll have completed the three-view of the bare front cross member though, and will post it here. The rest of the pieces will follow in the coming weeks... it takes time. That'll be my contribution.


ricreatr MSG #192, 09-06-2011 09:36 PM
      its a HUGE contribution, and i for one am extremely thankful!

bse53 MSG #193, 09-08-2011 06:36 PM
      Just noticed this tidbit.

The SCCA autocross rules for the Prepared Class lists the Fiero with an alternate rear suspension-- double A-arm. Apparently at some time someone was modifying the cars enough it made it into the rules as an allowable suspension modification.

This is an exception to the rule that generally requires cars to retain the "original basic type of rear suspension" from the manufacturer.


aaron88 MSG #194, 09-09-2011 12:17 AM
      I suppose I should chime in here since I’m working on the same thing in my back burner mode (since I’m working on many projects at once). But here’s where I’m at working on my 88:
- Fundamentally, I feel if you are going to the trouble to change the suspension geometry you might as well change the bearing too as they are outdated as well.
- At first I was going to keep the rear knuckle and just change the bearing out for something that can handle a few races before it self destructs. The variety of 5-100 rims available with acceptable offsets and rim widths is rather poor, so I decided to go with something that has basically what I need and readily available…Corvette C5 (not Z06 – rims wider than needed). Long story short, S10 4x4 front bearing pulled apart, hub pressed onto a common bearing for Ford, Mazda and Jaguar. Knuckle re-machined to accept said bearing. Make a retaining cup. Change to coil-overs. Rear end done! Right? Nope, like we know from this thread and others, the rear end still does not gain enough negative camber. But for those that don’t care about that it’s a nice upgrade for the rear.
- Note: above is what I have done so far, below is what I’m now working on
- My current thought to gain more negative camber on the rear while being abele to have close to zero static camber is to pocket the frame rail and add mounting points for an upper A arm inside that pocket. Make an adapter for the strut mount that allows pivot.
- This is about as far as I’m willing to go with the re-design of the rear end. Once I have something in CAD I’ll make a decision whether it’s worth the change or not.
- For the front, I have Corvette C5 front knuckles that will be installed stock with custom A arms, and adapters to go from vette(or whatever) to Fiero(or whatever). To keep service costs down, ball joints will not be Vette and the bearing will have an alternative but retain the wheel with stock spacing. My cost on a C5 front bearing is $330 Canadian. I’m not sure it’s worth it. It’s not the cost so much, I just don’t trust that it’s really that much better. I’d rather tell GM to shove it and find something else that will work. Sorry about the little rant but Corporations piss me off.


For those that are going to ask me a bunch of questions, please be advised. I’m not putting a lot daily hours into this, I don’t come here often and I post very rarely. I will be reading from time to time as I’m interested and can contribute.

Let me also say that I have not included many details as it would take a lot of time to convey and would add little to the design phase (from my standpoint). For example: When I say things like "pocket the frame rail", it should be assumed that the frame rail will be reinforced to allow for the new loading. Until such time that I have a working CAD model and can asses for stresses and shock loading, add reinforcement until I have at least a 2.5 safety factor and determine if it's reasonable to add such reinforcement, or if an alternative solution should be examined.


.


Rickady88GT (rjkmfam@sbcglobal.net) MSG #195, 09-09-2011 02:07 AM
      I would not feel safe machining out the rear knuckles for a larger bearing. They are VERY THIN to start with. This is, if you implied that?

Tha Driver MSG #196, 09-09-2011 04:28 AM
     
 
quote
Originally posted by aaron88:

- My current thought to gain more negative camber on the rear while being abele to have close to zero static camber is to pocket the frame rail and add mounting points for an upper A arm inside that pocket. Make an adapter for the strut mount that allows pivot.
.

This is exactly what I have in mind for the solo project - assuming I ever get back on it (depends on finances & if I find a good engine cheap - looking for a 3.4 short block). But do you really need to pocket the frame rails? I was thinking that with a pretty stiff suspension you could just add mounts to the outside of the frame rails. I'll admit I have not done any measuring in this regard.... but with little travel & a static of near zero neg camber you could achieve the right neg camber for the little body roll you'd have.
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts



aaron88 MSG #197, 09-09-2011 10:37 AM
     
 
quote
Originally posted by Rickady88GT:

I would not feel safe machining out the rear knuckles for a larger bearing. They are VERY THIN to start with. This is, if you implied that?


I did. The Fiero knuckle has a 71.1mm ID and the replacement bearing has an 80mm OD. I need a lip to catch the bearing on the back of the knuckle so it doesn't slide out the inside. The knuckles are grey cast not aluminum. "very thin" mans what anyway? What thickness do I require to maintain a reasonable safety factor?

If the knuckle fails I can use a smaller bearing or make a billet knuckle, or weld up a steel one.

.


aaron88 MSG #198, 09-09-2011 11:59 AM
     
 
quote
Originally posted by Tha Driver:
But do you really need to pocket the frame rails? I was thinking that with a pretty stiff suspension you could just add mounts to the outside of the frame rails. I'll admit I have not done any measuring in this regard.... but with little travel & a static of near zero neg camber you could achieve the right neg camber for the little body roll you'd have.
~ Paul


You kind of answered your own question. How much travel do you want? Once I have a CAD model it will answer the question better. Your mounting distance and angle will be dependent on your spring rate. You basically have to work it backwards because every time you change your spring rate or your ride height you will need to modify your mounting position on the inside.

Everything has to be worked backwards to what most people are thinking. It goes more like this:
1) How many lateral G's do I reasonably want to make.
2) How much do I want to spend on tires?
3) Assuming that you have worked out a ratio between 1 and 2, you can now determine the width of tire you need to maintain your required patch of tire to road contact based on the weight of the individual loads
3b) Is the tire I calculated available? If no then go back to 1 and start over with a fresh frame of mind.
4) Will my existing suspension geometry and characteristics allow me to maintain that contact patch?
5) If no to 4, then we find ourselves here at this thread. And things get rather complicated because there are an infinite number of ways to achieve the desired results which will very from person to person, and car to car.
6) How much suspension travel do you want? (assuming the minimum that will suit your needs) Every different length of travel requires a different length of upper arm or mounting point. (for me it's 3" (for now) in compression to the stop). Also note: this answer along with your suspension geometry will set your spring rate.
7) What ride height are you targeting? (assuming the minimum that will suit your needs) Every different height requires a different mounting point. (for me it's 5")
8) Set a target time and budget to obtain your results. Please note that within this constraint you may not achieve 4) even after modification
9) Here's where all hell brakes loose because there are too many different paths to continue a list. Honestly I should have stopped after number 1)


.


Bloozberry MSG #199, 09-09-2011 07:16 PM
      Finally a bit of progress to report. Here's the three-view drawing of the '88 front cross member. By itself, the cross member drawing is rather useless so I won't post any higher resolution pictures of the drawings here, suffice to say that progress is being made though. One notable exception is that the upper front control arm mount is angled 5 degrees. If you want a better view of the dimensions you can pull up individual views in my build thread here: www.fiero.nl/forum/Forum3/HTML/000116-11.html . Next up, the control arms.



wftb (danjesso@bmts.com) MSG #200, 09-09-2011 11:29 PM
      blooze you are incredible , thank you .

ricreatr MSG #201, 09-20-2011 08:53 AM
     
 
quote
Originally posted by bse53:

Here's the effect of raising the inboard mounting points of the lower control arms. I think. I think the previous owner raised them. Right now the cradle ride height is 4" on 15" slicks with a 22.9" diameter.




just noticed this. interesting that your axle seems to be going uphill toward the engine even after lowering. how much farther off the ground is the bottom of your trans compared to the bottom of the cradle?
do you have a pic of the other side to show us how close those mounts are to the trans? i know i have no room to move mine up at all.
thanks


Bloozberry MSG #202, 09-21-2011 09:06 PM
      For those interested, I posted a three-view drawing of the '88 front upper control arm in my build thread in the construction zone. Rather than duplicate the drawings in both threads, I'll post notices in this thread when I add individual drawings to my build thread. I will however post the completed assembly in here once it's done and analyzed.

Will (william.lucke@gmail.com) MSG #203, 09-22-2011 11:37 AM
      Don't forget to post a link for the lazy.

88GTS (avanvuuren@shaw.ca) MSG #204, 09-22-2011 07:37 PM
      http://www.fiero.nl/forum/F.../HTML/000116-11.html

bse53 MSG #205, 09-23-2011 06:36 PM
      It's the angle of the photo that is deceiving. Both the lower adjustable links and the axle are angled down to the transmission.





The axle clears the lower control links on the driver side by about 3/4". It looks like the cradle has been lowered about 1". Right now the cradle ride height is about 3.5". The transmission pan is about flush with the bottom of the cradle. (Actually it's below the cradle as the builder added an extension on the pan to increase the oil capacity.)



ccfiero350 (chuckcamp@gmail.com) MSG #206, 09-24-2011 08:32 AM
      Man, thats low.



Bloozberry MSG #207, 09-29-2011 09:22 PM
      Another update: I completed the three-view drawing of the 88 front lower control arm and posted it in my build thread (link is posted by 88GTS above). Next up is the knuckle.

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #208, 10-05-2011 05:51 AM
      http://blogs.insideline.com...sion-walkaround.html more suspension design pr0n.

ricreatr MSG #209, 10-10-2011 07:55 AM
      awww, awsome stuff in that link guys!!! save, save . . .

and thanks for the shots on that lowered 88. it sure does look different/better from the different angles!


Bloozberry MSG #210, 10-10-2011 08:43 AM
      Another update: I recently completed the three-view drawings of the '88 front knuckle and bearing assembly and posted them in my build thread above. I should have the complete front suspension drawing package finished up soon, and again, I will post the analysis here.

ricreatr MSG #211, 10-11-2011 05:18 PM
      thanks again for sharing blooz! cant wait to see the rest!

i have been researching tall upper ball joints today. it is common in s10 and early camaros to get a 1/2" taller joint.
how much would this help? the gains in those cars were very significant, and there were ways to tune out bumpsteer.
i could not find any info on tapers, but maybe the knuckles could be reamed to fit?
http://www.proforged.com/pa...all-Upper-Ball-Joint
such as these


Bloozberry MSG #212, 10-14-2011 05:08 PM
     
 
quote
Originally posted by ricreatr:

It is common in s10 and early camaros to get a 1/2" taller joint.
how much would this help?


I could take an educated guess at the impact of installing taller ball joints, but then the whole purpose of doing these drawings is to have a model to see first-hand what happens.

On that note, I keep chugging away at these component drawings for the front suspension. The latest ones were added to my build thread today: upper and lower ball joints, and the front uper control arm mount. All that's left is the tie rod now.


Bloozberry MSG #213, 11-16-2011 08:56 AM
      For those interested, I've added the following drawings to my build thread posted above:

- three-view front tie rod;
- complete OEM '88 front suspension assembly side-view; and
- complete OEM '88 front suspension assembly rear view

I'm currently working on the top view of the entire suspension assembly, which will be followed by a basic analysis of the suspension geometry.


aaron88 MSG #214, 11-16-2011 04:28 PM
      Update on my design

Before I went though the trouble of designing the double A-arm I wanted to try to solve the camber issue using the existing strut tower as this would significantly reduce the cost and build time. As it turns out I had no problem redesigning the lower control arm and engine cradle to accommodate my desired camber gains.

I was able to gain enough camber that even with body roll (between 1.7 and 3.5deg) I still had –1 degree to the road surface on the outside tire and +1 degree on the inside tire. Therefore for all those that wanted the double a-arm it seems that you don’t need it.

Keep in mind that although I checked for different body rolls there is separate geometry needed based on how much body roll you want (how stiff are your springs). I gained the camber by introducing a significant amount of anti roll. I didn’t use any anti-squat (as I don’t want any). However I will use anti-dive in the front.

So far I have 2D cad only (and only on the rear as I will do that first). The drawing is so basic that if I posted pics most would not understand what each line means (it’s a vector drawing only). I will post something when I have the 3D CAD done (sometime after December).

Also I have been assuming that I wanted about 3” of suspension travel with about 2 degrees of body roll (gives me about 1" vertical tire travel at max lateral G with about 2 degrees body roll. ie 325 lb/in rear spring). But if someone wants to chime in here and tell me why I might want more travel for street use I’m all ears. Also please keep in mind that since I’m still in early design phase I can still achieve almost any degree of body roll with almost any amount of camber, coupled with a wide variety of spring rates (by introducing more or less body roll via the roll center height). So far I have decided to keep the roll center above the bottom of the body frame (even at 3.5 degrees of body roll). So... that being said please ignore existing suspension characteristics as there will be no relation.

.


2002z28ssconv MSG #215, 11-17-2011 05:35 PM
      Been lurking and reading, and reading... My interest is also for the race driven Fiero. Even if I drive it on the street every now and then, current project Fiero needs to be optimized for cornering ability while driven in anger.

Today I sat down with Bloozberry's insanely wonderful drawings (I wish I could give more than one "+") and did some math. I'm not a suspension expert by any stretch of the imagination, but I have read all of this and stayed in a Holiday Inn last night, so it's kinda sounding logical to me. Here's what I came up with. What do you think? Is my logic (and math) valid?

If the two lateral links were to be moved up 3 cm (just over an inch) the maximum camber gained before the strut>knuckle>cradle angle exceeds 90 degrees is approximately 2.2 degrees over the stock mounting locations.

The camber increase using stock mounting was 2.047. But at this point a stock car probably has more body roll than 2 degrees, so the end result would be positive camber in relation to the pavement.

The raised mounting location yielded 4.238. However my calculation was based on the shorter of the two links. The reason why I calculated the camber change using the shorter link lies in the following question, and what I assume the answer to that question to be....

I don't have any of your fancy simulation software so all I can do is imagine the parts in my head. Wouldn't the shorter front link induce bumpsteer? My imagination says it would pull the front of the hub inward as it moved upward at a faster rate than the rear arm would. Is this small amount of bumpsteer actually desirable or not?

If it's desirable for some reason then my calculation would need to be revised because the longer arm was not taken into consideration. But the longer arm should shift the camber just a smidge higher. So my numbers are conservative estimates.

If the bump steer isn't wanted, why not move the rear mounting point on the cradle outward 3 cm (per BB's drawings)? The axis for the lower links would be parallel to the hub's axis.

With the bump steer gone, we move on to the camber. Moving the mounting point an inch higher would add a couple degrees of camber under compression of the suspension. I know, I know, the front link would hit other components already occupying that space... But what if you moved that mounting location further to the front of the car? As long as the pivot point remained on the same axis as before, the suspension (hub) would still travel in the same path. You would need a shorter link for the rear and a much longer link in the front but I think this would solve the clearance issue? If that logic is vaild, we could go all out and move the mounts upward, but rather than making both match the shorter link, shift the front link upward, towards the front... and inward to match the longer link's length.

This was calculated at the point in motion that the strut would start traveling back toward the center of the car, loosing negative camber. The shocks would be compressed 11.6 cm (~4 1/2") at this point, which is probably more than any of our cars will ever see. But the camber change rate is very small at that limit of the suspension travel, I can do more math to show what the calculated camber would be at intervals, but I didn't think it was necessary at this point. I just want to know if there are flaws in my logic at this point. Then I can calculate body roll, spring rates and maximum expected camber at the maximum point of suspension compression.


fieroguru MSG #216, 11-17-2011 07:14 PM
     
 
quote
Originally posted by 2002z28ssconv:
I know, I know, the front link would hit other components already occupying that space... But what if you moved that mounting location further to the front of the car? As long as the pivot point remained on the same axis as before, the suspension (hub) would still travel in the same path. You would need a shorter link for the rear and a much longer link in the front but I think this would solve the clearance issue?


The problem with moving the link location by the transmission forward, is that the links also must follow the arc of the trailing link. Angling the front link forward for clearance around the transmission would most likely result in binding or excessive toe changes.

I would lower the link location at the upright by bolting on a tube that will accept the long cross bolt and attach it below the stock placement. One could use the original cross bolt holes for attachment and also a portion of material could be added that ties into the mounting location for the trailing link. It has been said that this would increase the side loading on strut, but lowered fieros have more the strut shaft in the strut housing as well to help support the additional side loading.

It might help to visualize the outer link attachment point in this pic to be 1" lower. There is a nice open area on the upright to install this lower attachment (but you may need to run larger diameter wheels to clear the lowered position):

[This message has been edited by fieroguru (edited 11-17-2011).]

Bloozberry MSG #217, 11-17-2011 07:54 PM
      Thanks for contributing to this thread 2002z28ssconv. It sounds like you've put a fair bit of thought to your comments. (If it had been me though, I think I would've gone down to the hotel bar instead) You've already started thinking about how to modify the rear suspension geometry while I'm still stuck finishing up the front assembly drawings. To be frank, I haven't spent any time assessing modifications yet, but I'll see if I can provide some feedback on you're thoughts.

 
quote
Originally posted by 2002z28ssconv:

I'm not a suspension expert by any stretch of the imagination...


Excellent, you'll be right at home with the rest of us blind people trying to lead the other blind people!

 
quote
Originally posted by 2002z28ssconv:

I don't have any of your fancy simulation software so all I can do is imagine the parts in my head.


Join the club... these drawings are done the unsophisticated way... basically an electronic etch-a-sketch with the added feature of an erase button instead of having to shake the screen.

 
quote
Originally posted by 2002z28ssconv:

Wouldn't the shorter front link induce bumpsteer? My imagination says it would pull the front of the hub inward as it moved upward at a faster rate than the rear arm would. Is this small amount of bumpsteer actually desirable or not?


Your intuition is correct. The greater the compression of the rear suspension, the more the rear tires toe-in. Conversely at the front end, the placement of the outer tie rod end outboard of the plane described by the upper and lower ball joints should make the front wheels toe-out slightly under compression. I assume GM designed the suspension this way to induce understeer, being safer and more predictable for the average driver with a tail-heavy car.

If you want a more neutral steering car, you can either design the understeer out of it with new geometry like you propose, or play around with spring and/or swaybar rates to achieve either more or less body roll at either end to limit the amount the suspension compresses and therefore toes-in or out depending on which end of the car we're talking about. How much the rates should change is beyond the level of understanding that I'm at currently. I suspect most people just experiment on a trial and error basis using adjustable swaybars and/or swap springs until they're happy.

 
quote
Originally posted by 2002z28ssconv:

If the two lateral links were to be moved up 3 cm (just over an inch) the maximum camber gained before the strut>knuckle>cradle angle exceeds 90 degrees is approximately 2.2 degrees over the stock mounting locations.


I didn't check the math, but keep in mind that changing the angle between the strut and the lower control arms can be accomplished several ways. Raising the inboard link mounts seems feasible since there are some who have already done this without any interference from the transmission, so certainly that's a viable way. Another way is to move the top of the strut inboard. Finally if you're planning a widebody, you can use longer control arms to move the knuckle outboard, yet keep the strut top mount in the OEM location effectively making the angle between the links and the strut more acute.

 
quote
Originally posted by 2002z28ssconv:
The camber increase using stock mounting was 2.047. But at this point a stock car probably has more body roll than 2 degrees, so the end result would be positive camber in relation to the pavement.


According to Road & Track (Sept '83), the '84 four cylinder car reported roll angle (which was probably more heavily sprung than the '88 GT's, and a lighter car too) was 3.5 degrees per g. If I understand this correctly, given the max lateral acceleration of the '88 stock car with stock tires being about 0.83g (R&T Oct '87), then the max roll angle would be (0.83 g X 3.5 deg/g) = 2.9 degrees. Bearing in mind further research would have to be done to get a better roll angle rate for the '88, it's a start.

As for the effect of raising the mounting point of the forward inboard lateral link, and moving it forward and inboard, it's too much for my tired brain right now. Certainly something to look further into though. Maybe others can comment on this with their thoughts.


aaron88 MSG #218, 11-17-2011 10:14 PM
      Your on the right track. To achieve my results I have lowered the knuckle mounting point about an inch, deleted the trailing link, and mounted the front link (now lower control arm) in about the same location as the trailing link was on the front of the cradle. I have moved the cradle mounting point up and outward (up over 3” in some simulations). Moving the front control arm forward has added stiffness and eliminated interference with the transmission.


.


Bloozberry MSG #219, 11-18-2011 07:51 AM
     
 
quote
Originally posted by aaron88:

To achieve my results I have lowered the knuckle mounting point about an inch, deleted the trailing link, and mounted the front link (now lower control arm) in about the same location as the trailing link was on the front of the cradle.


So you've gone from a three link design to a single LCA like the '84-'87's? Time for some pictures or drawings of this.

[This message has been edited by Bloozberry (edited 11-18-2011).]

Will (william.lucke@gmail.com) MSG #220, 11-18-2011 07:53 AM
     
 
quote
Originally posted by aaron88:
Also I have been assuming that I wanted about 3” of suspension travel with about 2 degrees of body roll (gives me about 1" vertical tire travel at max lateral G with about 2 degrees body roll. ie 325 lb/in rear spring).
.


In my opinion, that's pretty slim. I think Fieros stock had 4"ish of jounce travel... might want to allow for 5 degrees of body roll also. Transient roll during rapid transition maneuvers is going to be greater than the steady-state roll for which you're designing.

[This message has been edited by Will (edited 11-18-2011).]

2002z28ssconv MSG #221, 11-18-2011 12:32 PM
     
 
quote
Originally posted by aaron88:

... (now lower control arm) ...


.


Actually that's kinda what I had in mind too. After Blooz mentioned the loss of lateral strength if the front link was at an angle, I had a vision of connecting the front link to the rear link which would create more a control arm.

I'll make a sketch tonight so you can see what I'm thinking about.


aaron88 MSG #222, 11-18-2011 11:14 PM
      The suspension is capable of more travel, the 1” jounce at 2 degrees is just what I calculated to obtain my desired spring rate. I’ve included for the majority of variables so the variance should be only moderate once I hit real world. I’ll record the actual figures and make adjustments to the design. Then repeat as required.

I don’t have 3D CAD yet but I’ll clean up a vector sketch so you can see the top view of the lower control arm. At present I’m planning to use three ball joints and one polly or rubber mount.



.

[This message has been edited by aaron88 (edited 11-18-2011).]

2002z28ssconv MSG #223, 11-19-2011 12:01 AM
      Here's what I was thinking...






While drawing these I noticed that the axis running through the inside joints of the lateral links is almost perfectly in line with the front pivot of the trailing arm.
But the trailing arms pivot is higher than the lateral links' axis. So they don't intersect. But right now the three pivot points almost share a common axis.

Moving the front lateral link's pivot inward will move the axis away from the trailing arm. I think this is going to cause binding and stress on the links and mounting points if we lock the two lateral links together.
They'd be fighting against the path that the trailing arm wants to take. Yes we could remove the trailing arm all together. But I'd rather keep the trailing arm for now. I expect to be putting a huge amount of power into this car and don't think that removing that bar would be a good idea. At least not for me. Plus from what I was reading on the other "build thread" removing the trailing arm would affect the anti squat calculations. I haven't quite got my head wrapped around that formula yet.

So I left the axis and trailing arm as they were, just moving the front link forward. This will reduce stress and still allow the lateral links to move upward for additional camber.

I really don't know how much deflection would occur under heavy side load. But just in case, a simple solution would be to either weld a bar between the two lateral links to triangulate the angles, or my preference, welding an attachment point onto each link so that another adjustable bar with rod ends could be attached. They would still be triangulated but you could tweak the length of that third arm when the length of the other two are adjusted for the allignment.


I haven't forgotten about moving the outer pivoy points downward. I just don't have a good solution for how to do that yet.

[This message has been edited by 2002z28ssconv (edited 11-20-2011).]

2002z28ssconv MSG #224, 11-19-2011 12:06 AM
     
 
quote
Originally posted by aaron88:

The suspension is capable of more travel, the 1” jounce at 2 degrees is just what I calculated to obtain my desired spring rate. I’ve included for the majority of variables so the variance should be only moderate once I hit real world. I’ll record the actual figures and make adjustments to the design. Then repeat as required.

I don’t have 3D CAD yet but I’ll clean up a vector sketch so you can see the top view of the lower control arm. At present I’m planning to use three ball joints and one polly or rubber mount.



.



This is the same as my third picture but with the front lateral link removed, right?


Will (william.lucke@gmail.com) MSG #225, 11-20-2011 03:05 PM
     
 
quote
Originally posted by 2002z28ssconv:

While drawing these I noticed that the axis running through the inside joints of the lateral links is almost perfectly in line with the front pivot of the trailing arm. But right now the three pivot points almost share a common axis.


Coincidence. Not relevant to the design at all.

 
quote
Originally posted by 2002z28ssconv:
Moving the front lateral link's pivot inward will move the axis away from the trailing arm. I think this is going to cause binding and stress on the links and mounting points if we lock the two lateral links together.
They'd be fighting against the path that the trailing arm wants to take.


Not the case at all for either rubber bushings or spherical bearings.

This would only be a problem if you used single axis hard bushings or bearings in the lateral links.


lateFormula MSG #226, 11-20-2011 04:06 PM
     
 
quote
Originally posted by 2002z28ssconv:

Here's what I was thinking...



This would not work. The forward control arm would not function with this configuration. The pivot axis at both ends of the control arm must be parallel to each other. What you show in that picture would cause the knuckle end of the link to rotate - the pivot axis would not hold it's horizontal position.


fieroguru MSG #227, 11-20-2011 05:53 PM
      Here is a very quick/rough mockup of how it would be rather simple to lower the outer links on the 88. In this mockup they are lowered 2 1/8" for reference purposes. If you used stock bushings, you would want to mill the upright for the thickness of the brackets, but if you are using rod ends, then you could shorten the spacers.




The unknown is how much lower you could go w/o having wheel interference issues, the the larger diameter, the more room you would have.


sspeedstreet (sspeedstreet@verizon.net) MSG #228, 11-20-2011 06:40 PM
      Hmmm. That would be a lot easier than raising the inner mounts.

2002z28ssconv MSG #229, 11-20-2011 07:02 PM
     
 
quote
Originally posted by sspeedstreet:

Hmmm. That would be a lot easier than raising the inner mounts.


I agree. I also took a look at a spare set of rear knuckles today. Guru is right on with his mock up. You really wouldn't even have to do any cutting or welding to the knuckle or cradle, just bolt these on.


2002z28ssconv MSG #230, 11-20-2011 07:15 PM
     
 
quote
Originally posted by lateFormula:


This would not work. The forward control arm would not function with this configuration. The pivot axis at both ends of the control arm must be parallel to each other. What you show in that picture would cause the knuckle end of the link to rotate - the pivot axis would not hold it's horizontal position.


Yep, you're right. I fixed my drawings.


Bloozberry MSG #231, 11-20-2011 08:15 PM
      For those interested, I posted the final top view drawing of the front suspension in my build thread, plus two tables of X-Y-Z coordinates which locate all of the front and rear suspension components in space. Zac88GT has already taken the coordinates of for the front suspension and produced graphs for the following:

Caster vs Bump
Camber vs Bump
Toe vs Bump
Front Swing Arm Length vs Bump
Side Swing Arm vs Bump
Anti-Dive vs Bump
Camber vs Roll
Roll Center Position vs Roll

These graphs enable the comparison of the performance of future modifications to the stock front suspension. I'm waiting to see if he can model the rear suspension in the same way.


Will (william.lucke@gmail.com) MSG #232, 11-20-2011 08:58 PM
     
 
quote
Originally posted by fieroguru:

Here is a very quick/rough mockup of how it would be rather simple to lower the outer links on the 88. In this mockup they are lowered 2 1/8" for reference purposes. If you used stock bushings, you would want to mill the upright for the thickness of the brackets, but if you are using rod ends, then you could shorten the spacers.
http://i152.photobucket.com...pension/IMG_9240.jpg
http://i152.photobucket.com...pension/IMG_9241.jpg
http://i152.photobucket.com...pension/IMG_9242.jpg

The unknown is how much lower you could go w/o having wheel interference issues, the the larger diameter, the more room you would have.


Looks like the toe link would hit the trailing arm...


fieroguru MSG #233, 11-20-2011 10:20 PM
     
 
quote
Originally posted by Will:


Looks like the toe link would hit the trailing arm...


Yeah 2 1/8" might be a bit too much, but there should be room for less of a drop.

[This message has been edited by fieroguru (edited 11-20-2011).]

Zac88GT (snarfboot@hotmail.com) MSG #234, 11-20-2011 11:23 PM
      Front and Rear graphs (combined) are now posted in Blooze's thread

ricreatr MSG #235, 11-21-2011 08:15 PM
     
 
quote
Originally posted by fieroguru:

Here is a very quick/rough mockup of how it would be rather simple to lower the outer links on the 88. In this mockup they are lowered 2 1/8" for reference purposes. If you used stock bushings, you would want to mill the upright for the thickness of the brackets, but if you are using rod ends, then you could shorten the spacers.



ok, i will bite. i think this is genius! i keep staring at these photos, thinking it cant work. but i like it.
is the ear strong enough to take the side loads that would get moved down to it?
how far can the tube get moved toward the wheel to correct the scrub radius before things hit the rotor?
by fixing the scrub radius could you eliminate the twisting the knuckle gets under acceleration?
you would have to move the tube out some, as it drops to avoid making the scrub radius worse.
could you change to a triangulated lower control arm to eliminate the trailing link (and its interference)
would we be better off keeping the trailing link for the lifting properties it gives?
how soon will someone do a graph to show the amount of improvement in camber gain?
how soon will it be before you make a set?


fieroguru MSG #236, 11-21-2011 09:50 PM
     
 
quote
Originally posted by ricreatr:


ok, i will bite. i think this is genius! i keep staring at these photos, thinking it cant work. but i like it.
is the ear strong enough to take the side loads that would get moved down to it?
how far can the tube get moved toward the wheel to correct the scrub radius before things hit the rotor?
by fixing the scrub radius could you eliminate the twisting the knuckle gets under acceleration?
you would have to move the tube out some, as it drops to avoid making the scrub radius worse.
could you change to a triangulated lower control arm to eliminate the trailing link (and its interference)
would we be better off keeping the trailing link for the lifting properties it gives?
how soon will someone do a graph to show the amount of improvement in camber gain?
how soon will it be before you make a set?


I wouldn't call it genius, just a degree of insanity. I am sure the lateral link location at the wheel could be dropped 1" and moved further outboard by 1" w/o issue (but probably not on a 15" wheel), but haven't any idea how much it would improve the camber curve and if it would be at the expense of another suspension characteristic.

After thanksgiving I will be pulling an 88 into the garage to document my 13" brake upgrade, and at the same time I will probably go ahead and make one of these relocation brackets to test fit and run it through full compression and full extension to prove that everything clears and find the limit at which the trailing link must be modified (offset the tube to the bottom side of the bushing to allow more clearance for the lateral/toe link). The tabs on the end are 3/16" steel and they will be drilled for the long bolt sleeve to pass through them and be welded solid from the back side. That in addition to the support that can tie back to the trailing link ear should be stout enough to work w/o deflection issues.

I am not a big fan of eliminating the trailing link on a stock cradle for 2 main reasons.
Doing so would require relocating one of the inboard links, then triangulate the setup, then hope the inboard mounts hold at the cradle as they were never designed to support the braking/acceleration and road bump forces.
It would also kill one of the best features of the 88's... separation of the lateral and fore/aft forces. Since they are separate, you can run rod ends for lateral control/precision and rubber bushings in the trailing link to minimize road/bump harshness. Once you make the lateral links pull double duty, lateral control via stiffer bushings/rod ends will come with an increase in ride harshness.



fieroguru MSG #237, 11-22-2011 06:06 PM
      Here is a little proof of concept mockup. I fabbed up some better brackets to lower the lateral link and trailing link locations at the upright 1 1/2" just to see where things ended up. This modification would restore the suspension geometry back to stock for a fiero that is lowered 1 1/2".





The trailing link gets pretty close to the 16" wheel


There is still quite a bit of work to still be done from a reinforcing/gusseting standpoint, but it seems like a workable solution.



Zac88GT (snarfboot@hotmail.com) MSG #238, 11-22-2011 08:58 PM
      Edited to verify results

[This message has been edited by Zac88GT (edited 11-25-2011).]

Bloozberry MSG #239, 11-22-2011 10:43 PM
      I'm a little suspicious about the anti-squat curve. It looks more to me like the program used the formula for a solid axle rather than an independent rear end. I've already shown in a previous drawing that the anti-squat for a stock '88 Fiero is about 28.4% which is the practical limit for an IRS, while your graph shows 75% at ride height for Fieroguru's modified lower links, and 58% for the stock config.

(Edited for more info)

[This message has been edited by Bloozberry (edited 11-23-2011).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #240, 11-25-2011 03:47 PM
      Cool, the discussion is finally heading in the direction I intended.

Bloozberry MSG #241, 11-25-2011 04:51 PM
      For those following this thread, you should probably ignore the curves Zac posted above until further notice. They were created using my data uploaded in his Lotus Suspension Analysis software, however I've since discovered several important errors that will change the nature of the curves. I've asked Zac to remove them until we can reconcile a few differences between the program's output and my data, so don't be surprised to see the original graphs disappear.

Once new ones are posted, one of us will let everyone know by posting a message stating as much. Thanks for your patience.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #242, 12-02-2011 12:41 AM
      Another good source: http://www.carbibles.com/suspension_bible.html
http://www.carbibles.com/suspension_bible_pg2.html
etc. (see link from the pull down menu)
http://books.google.com/boo...html?id=smKpTCICw8QC

[This message has been edited by Austrian Import (edited 12-02-2011).]

aaron88 MSG #243, 12-02-2011 01:56 PM
     
 
quote
Originally posted by aaron88:

Update on my design

Before I went though the trouble of designing the double A-arm I wanted to try to solve the camber issue using the existing strut tower as this would significantly reduce the cost and build time. As it turns out I had no problem redesigning the lower control arm and engine cradle to accommodate my desired camber gains.

I was able to gain enough camber that even with body roll (between 1.7 and 3.5deg) I still had –1 degree to the road surface on the outside tire and +1 degree on the inside tire. Therefore for all those that wanted the double a-arm it seems that you don’t need it.

Keep in mind that although I checked for different body rolls there is separate geometry needed based on how much body roll you want (how stiff are your springs). I gained the camber by introducing a significant amount of anti roll. I didn’t use any anti-squat (as I don’t want any). However I will use anti-dive in the front.

......

.


Update:

So I feel a little embarrassed about this, but I forgot to include for the tire deformation which adds an additional .6 degrees of body roll (275 tires). What I might do to compensate is reduce the anti-roll, as I'm back to the problem of not gaining enough negative camber. I could also increase static camber to -1 degree but I wanted to maintain it at -.2 to -.5. So back to the vector force diagrams for me.

If I can't solve this problem without making drastic (read expensive) changes I'll be on to the double control arm design...

.


Zac88GT (snarfboot@hotmail.com) MSG #244, 12-03-2011 10:28 PM
      Here are the suspension analysis results after the coordinates were confirmed by blooze. To begin I'll start with the layout views and then show each graph and any detail or information that may be pertinent in interpreting the graph.

Front View


Side View


Top View


Isometric View


Camber vs. Bump

-This graph follows the standard convention for +'ve and -'ve camber
-The number on either end of the axis scales correspond to the very end of the graph so in this case each graduation in the Y is 1 degree and each graduation in the X is 15mm

Castor vs. Bump

-Rear castor is flat across the bottom at 0

Kingpin vs. Bump


Toe vs. Bump

-Toe in is represented by -'ve values

Spring Motion Ratio vs. Bump

-At ride height the front and rear wheels will move ~1.87 and 1.10 times more than the spring respectively.

Damper Motion Ratio vs. Bump


Roll Center Z vs. Bump

-This is the height with a reference frame that is fixed to the body so ideally the movement in relation to the CG should be minimized for consistent predictable handling
-The roll axis of a car should also correspond to it's weight distribution. ie. a rear heavy car should have a roll axis that is closer to the CG at the rear than the front

Camber vs. Roll

-Only the Left side of the car is shown for clarity
-+'ve roll would be caused by a right hand turn

Roll Center Z vs. Roll


Roll Center Y vs. Roll


Roll Center Position (XY) During Roll

[This message has been edited by Zac88GT (edited 12-03-2011).]

Zac88GT (snarfboot@hotmail.com) MSG #245, 12-03-2011 10:37 PM
      Here are the changes that Fieroguru proposed (moving the lateral and trailing links down by ~1.5" or 40mm). The new curve is shown in green and superimposed over the original in blue to better show the effects of the change.

Camber vs. Bump


Toe vs. Bump


Roll Center Z vs. Bump


Camber vs. Roll


Roll Center Z vs. Roll


Roll Center Y vs. Roll


Roll Center Position (YZ) During Roll



Zac88GT (snarfboot@hotmail.com) MSG #246, 12-03-2011 10:48 PM
      Overall I would say the changes are an improvement. It certainly improves rear camber gain and roll center control but at the expense of toe out on bumps, although it's fairly minimal.

Will (william.lucke@gmail.com) MSG #247, 12-05-2011 12:15 PM
     
 
quote
Originally posted by Zac88GT:
-The roll axis of a car should also correspond to it's weight distribution. ie. a rear heavy car should have a roll axis that is closer to the CG at the rear than the front


The roll axis should be as close to parallel to the centroid axis as practical.


ricreatr MSG #248, 12-06-2011 10:29 AM
     
 
quote
Originally posted by Zac88GT:

Camber vs. Roll



if i am reading this correctly, in the lower left quadrant, it is telling me that if the car rolls 6.0* (say to the right) the tire will be at -2.5* to the ground? better than -6* to the ground, and also better than the previous -3*, but not where it should be yet. and it should be around 0*?

things would be a lot easier to understand if our cars would just voluntarily lean into corners like McQueen does . . .


mram10 MSG #249, 12-06-2011 05:23 PM
      Here comes a dumb question, so bare with me.

If I were to lengthen my a arms, would the lower and upper both be extended by the same amount, or would it be a ratio of stock length?


Zac88GT (snarfboot@hotmail.com) MSG #250, 12-06-2011 08:49 PM
     
 
quote
Originally posted by ricreatr:
if i am reading this correctly, in the lower left quadrant, it is telling me that if the car rolls 6.0* (say to the right) the tire will be at -2.5* to the ground? better than -6* to the ground, and also better than the previous -3*, but not where it should be yet. and it should be around 0*?


At 6* roll the inside tires will be at -5.66* and -3.45* and the outside tires will be at 2.91* and 4.76* for front and rear respectively. Keep in mind this is with zero steering input and zero static camber so these values would change a little depending on the steering input angle due to castor. Everything is about compromises, if you increase the camber gain you'll be better off in the corners but straight line braking will suffer.


Bloozberry MSG #251, 12-06-2011 09:22 PM
     
 
quote
Originally posted by mram10:

If I were to lengthen my a arms, would the lower and upper both be extended by the same amount, or would it be a ratio of stock length?


Not a dumb question at all... in fact a really good one. The answer is, that it depends. You can do either but most aftermarket companies extend them by an equal amount since that keeps certain static parameters the same as stock, like the caster angle, camber, kingpin angle, scrub radius, etc. Equally extended control arms do however change a few dynamic properties though like the rate of camber change, for example. The longer the control arms, the less camber change you'll get for a given amount of wheel travel.

If you knew what you were doing, you could design control arms that were overall longer, but by a different amount to help compensate for the slower rate of camber change. As with any change though, it usually results in undesired effects on some other aspect of the geometry though, so I'd stick with equally lengthened arms.




mram10 MSG #252, 12-06-2011 09:29 PM
      Great! Thank you. It will only be 2" per side on the front and back. I was going to cut the arms, connect via rod stock then use angle iron on top and bottom to add more support. I will make sure it isn't too close to the wheel. Sound good?

I guess I should have asked you ,what you would do?


Bloozberry MSG #253, 12-06-2011 10:20 PM
     
 
quote
Originally posted by mram10:

I was going to cut the arms, connect via rod stock then use angle iron on top and bottom to add more support. Sound good?


This isn't a good idea IMHO. I know from you're other thread that you're trying to get the best design features for the least cost, but cutting and lengthening the stock control arms is a dangerous idea. The stamped steel arms were designed as a continuous piece using finite element analysis and made from high strength steel to ensure sufficient structural integrity in bending, torsion, and compression. They would be significantly weakened by cutting them, and even more so by applying welding heat. Remember these are what keep the wheel pointed in the right direction and attached to the rest of the car under some fairly strenuous conditions.

 
quote
Originally posted by mram10:

I guess I should have asked you ,what you would do?


I have different constraints than you do since my build project isn't on a tight budget. I bought 3" extended tubular control arms to avoid the problems associated with wheel spacers, but they are quite expensive. Given your stated goals to stay within a certain cost, I would use wheel spacers/adapters in the rear since they have they least impact on suspension geometry back there.

For the front, it's a toss up. The right way to do it is with 2" longer control arms that have been designed by a reputable firm and welded by a certified welder. That way you keep the safety margins on a critical component of the car. If you really can't afford the longer arms, then wheel spacers/adapters are a far, far better way to get the right track width on your car than modifying the OEM arms. There will be a few handling quirks with wheel spacers on the front of the car, but nothnig that others haven't gotten used to in the past by going the same route.



mram10 MSG #254, 12-06-2011 11:14 PM
      Advice taken. I am now leaning toward the rear spacers and new front arms.

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #255, 12-09-2011 01:50 AM
      Zac88GT, great posts. This is where I expected this thread to go. Can't wait for more useful discussion.



ricreatr MSG #256, 12-09-2011 10:22 AM
      edit, not "redesign for better geometry" worthy.

[This message has been edited by ricreatr (edited 12-10-2011).]

Will (william.lucke@gmail.com) MSG #257, 12-09-2011 06:07 PM
     
 
quote
Originally posted by Bloozberry:

The stamped steel arms were designed as a continuous piece using finite element analysis and made from high strength steel to ensure sufficient structural integrity in bending, torsion, and compression.


Uhh... remember that these parts were designed in the late '70's/early '80s. (First appeared on Citation/Celebrity).
I don't think there was a lot of FEA involved...


Bloozberry MSG #258, 12-09-2011 09:28 PM
      Will, according to the Sept '83 issue of Road & Track Magazine in the Technical Analysis review: "Finite element analysis and high strength steels were used extensively...".

Now, with respect to the rear control arms, you may be right about them not being designed with FEA since they are virtually indistinguishable from X-car parts. Regardless, the discussion about cutting control arms was specific to the front suspension. If you read an earlier post by mram10 he asks: "If I were to lengthen my a arms, would the lower and upper both be extended by the same amount?" Clearly this is about the front.

As for the front, you might argue that the upper and lower control arms were designed long before the Fiero for the T-car (Chevette/Acadian) but the Fiero arms were designed specifically for the P-car. Again from R&T: "On the T-car, the shock mounts to the upper arm and stands very high in the wheel well. But to lower the Fiero's hoodline, the shock now mounts to an otherwise standard lower arm." Neither of the front control arms are carry-overs from earlier cars, so they may very well have used FEA.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #259, 12-22-2011 03:37 AM
     
 
quote
Originally posted by Will:
Uhh... remember that these parts were designed in the late '70's/early '80s. (First appeared on Citation/Celebrity).
I don't think there was a lot of FEA involved...


Well didn't they do FEA with a slide ruler and abacus back then? *I kid, I kid*


wftb (danjesso@bmts.com) MSG #260, 12-23-2011 12:22 AM
      i am installing an HT motorsports bumpsteer kit on my 86 gt .i noticed that as i jack it up and down that it has some negative camber gain under compression .kind of surprised me ,since the 84 -87 rear suspension is supposed to have terrible geometry and all .anyways , if this kit gets rid of my bumpsteer and works as well as my rear suspension did before , then i am done modifying the rear suspension .this picture shows tire to roadangle going through a corner at speed (with old suspension ) :

i could have gone a lot faster but the can am spyder in front of me kept slowing down , he was having trouble staying in the lane .i now own a spyder RS and i dont think he had many hours on it .takes a lot of practise to go through a corner at speed .this thread has kind of become an 88 suspension discussion so i thought i would inject a bit of 84 t0 87 in to it .after all , close to 92% of all fieros are in that category .


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #261, 01-04-2012 07:13 AM
      Good idea. It should include'84-'87 suspensions. Maybe even compares to '88.

Really hoping to see a double wishbone rear setup (that takes into account realistic mounting possibilitiesand clears the engine)


wftb (danjesso@bmts.com) MSG #262, 01-05-2012 01:56 PM
      i made an attempt at the double wishbone but gave up when i could not get the arms to line up the way i wanted .on the passenger side it would be easy to do .but on the driver side , a part of the f23 transmission i use hangs right over the cradle and is in the way of an easy way to do it .i have not totally given up on the idea , and now that i have the HT bumpsteer correction lower arms it means the uppers can be less complicated .but still have not figured out a simple way to do it .

Will (william.lucke@gmail.com) MSG #263, 01-05-2012 02:10 PM
     
 
quote
Originally posted by Zac88GT:

Toe vs. Bump

-Toe in is represented by -'ve values


Looks like the rack could be lowered a bit...


Will (william.lucke@gmail.com) MSG #264, 01-05-2012 02:15 PM
     
 
quote
Originally posted by Bloozberry:

Will, according to the Sept '83 issue of Road & Track Magazine in the Technical Analysis review: "Finite element analysis and high strength steels were used extensively...".

Now, with respect to the rear control arms, you may be right about them not being designed with FEA since they are virtually indistinguishable from X-car parts. Regardless, the discussion about cutting control arms was specific to the front suspension. If you read an earlier post by mram10 he asks: "If I were to lengthen my a arms, would the lower and upper both be extended by the same amount?" Clearly this is about the front.

As for the front, you might argue that the upper and lower control arms were designed long before the Fiero for the T-car (Chevette/Acadian) but the Fiero arms were designed specifically for the P-car. Again from R&T: "On the T-car, the shock mounts to the upper arm and stands very high in the wheel well. But to lower the Fiero's hoodline, the shock now mounts to an otherwise standard lower arm." Neither of the front control arms are carry-overs from earlier cars, so they may very well have used FEA.


I guess they could have done primitive FEA on a Cray that has fewer flops than a modern cell phone.

Lol... welding a u-bracket on the LCA to mount the shock is hardly a "redesign". I'm not sure there was *ANY* CAD involved in designing the front suspension... the two LCA pivots are not coaxial, for example.

[This message has been edited by Will (edited 01-05-2012).]

wftb (danjesso@bmts.com) MSG #265, 01-05-2012 07:52 PM
     
 
quote
Originally posted by Will:


I guess they could have done primitive FEA on a Cray that has fewer flops than a modern cell phone.

Lol... welding a u-bracket on the LCA to mount the shock is hardly a "redesign". I'm not sure there was *ANY* CAD involved in designing the front suspension... the two LCA pivots are not coaxial, for example.


why does having the pivots non coaxial mean anything ? they are on the same plane and they go up and down without moving the ball joint out of its intended path .look at the mustang 2 front suspension , it uses a similar idea :a main arm coming straight out at the wheel centre and then an arm that braces to the back to prevent distortion .it works .


Bloozberry MSG #266, 01-05-2012 10:12 PM
      If they're non-coaxial, the shorter leg will prescribe a tigher arc than the longer leg as it tries to pivot, but the trouble is that they are both part of the same rigid control arm. That means the only way the lower control arm can rotate is through the compliance of the rubber bushings.

wftb (danjesso@bmts.com) MSG #267, 01-06-2012 12:01 AM
      so there is too much binding ? there are a lot of similar designs in use here , i think mostly for packaging concerns but they still seem too work well .the perfect setup seldom fits in the allotted space .i have to go out to the garage , take a coilover off and run the arm up and down and see what happens .see you later .

wftb (danjesso@bmts.com) MSG #268, 01-06-2012 01:33 AM
     



going up and down and i apoligize for poor pics but not great light at night .but there is no camber gain or loss from bottom to top of travel of my 86 gt front suspension .not good but not terrible compared to most older north american built cars .it is hard to tell how much binding is going on since i have tubular arms with poly .but here is a challenge for those of you that have the software ....tell me what the affect is of the non coaxial inner mounts .the last pic is just showing what my suspension looks like .


Will (william.lucke@gmail.com) MSG #269, 01-06-2012 10:03 AM
     
 
quote
Originally posted by wftb:

why does having the pivots non coaxial mean anything ? they are on the same plane and they go up and down without moving the ball joint out of its intended path .look at the mustang 2 front suspension , it uses a similar idea :a main arm coming straight out at the wheel centre and then an arm that braces to the back to prevent distortion .it works .


If you have rubber bushings or spherical bearings, it's not a big deal.

If you have urethane or UHMW bushings, then the suspension will start to bind as it gets away from the neutral position.


wftb (danjesso@bmts.com) MSG #270, 01-06-2012 10:50 AM
      there is some binding in the motion of the lower control arm .it is not extreme .i noticed that when i first put on the tubular arms and i chalked it up to the way the poly is jammed against the mounts .i have some delrin bushings i was going to put in sometime , i am thinking they might not be such a good idea because they are so rigid .

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #271, 01-26-2012 12:55 AM
      Bump

zkhennings MSG #272, 01-26-2012 05:12 PM
      So I am new to all of this but I am in school to be a Mechanical engineer and in my kinematics class right now we are doing lots of problems that are related to suspension geometries so only recently I have gained some real knowledge on the subject of suspension design and I have been coming up with some ideas. I have been doing drawings of proposed geometries of a strut type suspension, and it seems to me that an ideal set up would utilize a steeply angled strut with long lower links at a slight downward angle when the car is siting at ride height. So would lengthening the lower links and raising the attachement points to the cradle not only increase the track width and lower the lateral load, but also increase the camber curve because the longer links will displace more, the angle of the links will create a decent amount of negative camber, andd pushing the knuckle out farther will also steepen the angle of the strut? I have an 85 so for me its all A arms and such. Is there a way to move the mounting point of the strut to the tower in the pre 88s to move them farther in and put the struts at a steeper angle?

FieroWannaBe (patond@alumni.msoe.edu) MSG #273, 01-26-2012 10:12 PM
     
 
quote
Originally posted by zkhennings:

So I am new to all of this but I am in school to be a Mechanical engineer and in my kinematics class right now we are doing lots of problems that are related to suspension geometries so only recently I have gained some real knowledge on the subject of suspension design and I have been coming up with some ideas. I have been doing drawings of proposed geometries of a strut type suspension, and it seems to me that an ideal set up would utilize a steeply angled strut with long lower links at a slight downward angle when the car is siting at ride height. So would lengthening the lower links and raising the attachement points to the cradle not only increase the track width and lower the lateral load, but also increase the camber curve because the longer links will displace more, the angle of the links will create a decent amount of negative camber, andd pushing the knuckle out farther will also steepen the angle of the strut? I have an 85 so for me its all A arms and such. Is there a way to move the mounting point of the strut to the tower in the pre 88s to move them farther in and put the struts at a steeper angle?


The problem with your proposed solution is how it will affect roll center placement (factors of the instant centers and force vectors), migration and control. The difference in the 88 to the citation derived suspensions is incorporating modest changes like what your suggesting. But doing so to an extreme wont cure all the handling problems it can make them worse. There is more to the solution of stable and predictable handling than camber gain, Ideally it is maintaining the tire perpendicular to the road during roll. Roll stiffness is important too, which is what makes roll center placement important. Anti dive and squat are used to maintain perpendicularity of the tire during accel/deccel forces causing suspension movement and therefor camber change. Another important aspect of suspension design is to incorporate an amount of rear toe-in and front tow out during roll on the outside wheel. This will fight oversteer.
Does your university offer any vehicle dynamics class? I really suggest you take one if you have the opportunity. Mine wasn't very in depth, but a decent start. Try to get a hold of Race Car Vehicle Dynamics by Milliken, everything your wondering, and interested in knowing can be explained to some extent within that book, and you will have the understand to take advantage of it. Try to get involved in SAE Formula and Formula Hybrid, and you'll learn tons though application.

Changing the pre 88 to extremes would be hard, there is only so much room on the knuckle to regain static camber to a reasonable amount if the strut top is moved inboard (unless your looking to be some baller hellaflush cruiser), and there are few knuckles with the same or more inclination to the strut mounting than what the Fiero has. raising the inner control arm pivot could be done with some work on the cradle by welding some rectangular stock to place the bushings (1+" of gain?), but the toe-link needs major rework in length and position to control excessive toe-change (i guess it does already though).

Edit to add:
If you were to move the strut top inboard, the control arm should become much longer with a slightly higher inner pivot, and roll center will not be as terrible, but still not great ( a major downfall of strut based suspensions) The fiero rear doesn't have the room for long control arms.

[This message has been edited by FieroWannaBe (edited 01-26-2012).]

zkhennings MSG #274, 01-27-2012 05:35 AM
      I go to WPI and I am part of fsae but unfortunately when it comes to design it is mostly done by a small team of seniors who work on the car for their MQP and the ones of us in the club who are not on the MQP team just help build the car drive it and test it. I do have some courses like that but kinematics is a prerequisit so I will look into taking one next year. And I have race car vehicle dynamics its a huge book I downloaded the pdf and printed it and hole punched it and put it in a binder. Im slowly working my way through it. I thought angling the A arms and steepening the pitch of the lower links would move the roll center up closer to the cog? I was under the impression that you want roll center close to cog?

Bloozberry MSG #275, 01-27-2012 08:16 AM
     
 
quote
Originally posted by zkhennings:
I was under the impression that you want roll center close to cog?


What's more important is to have the roll center located at the ideal vertical distance from the CofG (bear in mind that the location of the roll center is always changing in most cases). It's about compromises. If you agree that you want a suspension that absorbs road shocks, then you must accept body roll as a side effect. To counter body roll, you need a suspension that generates the optimum amount of camber to offset the body roll. One of the ways this is achieved is by tuning, not eliminating the vertical distance between the CofG and the roll center. Reducing the vertical distance between the roll center and the CofG reduces the amount of roll for any given speed around a corner, but isn't necessarily a good thing depending on the design of the suspension. What you want is the right amount of body roll to cause the suspension to induce the right amount of camber. In any case, raising the roll center is not usually the best way to tune this characteristic... the best results come from lowering the CofG instead.


FieroWannaBe (patond@alumni.msoe.edu) MSG #276, 01-27-2012 09:11 AM
     
 
quote
Originally posted by Bloozberry:
What's more important is to have the roll center located at the ideal vertical distance from the CofG .

I agree with Bloozberry here. A high roll center creates jacking forces on the body, it does reduce roll moment though. Roll center placement is not an exact right or wrong, designers have their own opinions and reasons on where they like it, some prefer them to be low, others around CoG, it also can go off of driver preference. But a moving roll center is never good, it leads to unpredictable handling, so its best to try and keep it around the same area during roll. Speed in corners comes more from driver confidence and car control than all out grip. Fieros arent Formula racers, so all out grip is NOT as important as driver confidence (IMO), predictability, and durability. I would rather race an always understeering car than a nuetral car that snaps into oversteer and inoportune moments. I can fight understeer, and adjust my driving style to suit, I will underdrive a car that I feel will not remain stable at its limits.

[This message has been edited by FieroWannaBe (edited 01-27-2012).]

FieroWannaBe (patond@alumni.msoe.edu) MSG #277, 01-27-2012 09:24 AM
     
 
quote
Originally posted by Bloozberry:
Reducing the vertical distance between the roll center and the CofG reduces the amount of roll for any given speed around a corner, but isn't necessarily a good thing depending on the design of the suspension. What you want is the right amount of body roll to cause the suspension to induce the right amount of camber. In any case, raising the roll center is not usually the best way to tune this characteristic... the best results come from lowering the CofG instead.


A reduced roll center to CofG height can also combat dynamic body roll, making it harder for the CofG to roll to the outside relative to the tires, which for extremely soft suspensions mean less load transfer (say, in a very wide and heavy big block trans am). But as the roll center is raised the force vector from the tire patch to the roll center will try to raise the body, and you will lose load transfer on the outside tire (if I remeber correctly).


zkhennings MSG #278, 01-27-2012 01:19 PM
      Ok, so should I bother trying to move the strut inwards at all? (pre 88) to at least the point of the 88? Has anyone done this? I know when people swap an 88 cradle they have to relocate the rear strut attachment point, I figured Id do something similar. Also, do you want positive camber gain to be equal to negative camber gain? (when suspension is dropping of course) or do you want the inside wheel to end up flat and so positive camber a little more to compensate for the static camber? I know that the outside wheel should not be totally flat against the pavement, the whole "a tire on edge wants to turn" like on a motorcycle, but should the inside be flat?

FieroWannaBe (patond@alumni.msoe.edu) MSG #279, 01-27-2012 02:50 PM
     
 
quote
Originally posted by zkhennings:

Ok, so should I bother trying to move the strut inwards at all? (pre 88) to at least the point of the 88? Has anyone done this? I know when people swap an 88 cradle they have to relocate the rear strut attachment point, I figured Id do something similar. Also, do you want positive camber gain to be equal to negative camber gain? (when suspension is dropping of course) or do you want the inside wheel to end up flat and so positive camber a little more to compensate for the static camber? I know that the outside wheel should not be totally flat against the pavement, the whole "a tire on edge wants to turn" like on a motorcycle, but should the inside be flat?

Idealy the rear tires should be flat as much as possible, anything less than flat and you will lose tractive capability. Camber thrust is more usefull on the front axle to aid slip angle turning force. Strut inclination like the 88 wouldnt be terrible, it can help the camber curve, but how will you regain static camber? the knuckle is now pivoted inboard. linear camber gain is hard to accomplish while maintaining a decent roll center, but idealy yes, camber lost and camber gained in bump and jounce should mimic body roll angle.
So if the body rolls 5 degrees, the outside tire would loss 5 degrees of camber, and the inside gain 5. Before anything is done, take a look at where the roll center for such a setup would be compared to stock, take some simple measurements when the car is on the ground of where all the pivots are.
The best improvement you can make to the pre 88 suspension is to limit movement. it's BIGGEST flaw is a solidly mounted toe link and compliantly mounted control arms and struts. The unloading of the rear suspension will cause rear toe-in , and mid turn, while lifting the throttle, the car will move from an understeer situation into oversteer. The lack of adequate anti-dive/anti-squat makes this very hard to control.
I would concentrate some kinematic analysis on how the toe link affects toe change throughout the suspension movement, including some level of bushing deflection.



zkhennings MSG #280, 01-27-2012 10:07 PM
      Ok, I was actually doing that (seeing where I should put the tierod/how long it should be for useable suspension travel) But I have poly bushings and Kyb struts and an anti roll bar in the back along with solid mounted cradle bushings. So I figured the next step was to improve camber curve and then put the toe link in the right place for the amount my suspension moves. Is there a way that I can move the strut in more? And can antidive/squat be clarified for me? This is all really helpful though thanks

zkhennings MSG #281, 01-31-2012 01:47 PM
      What do you guys think of this bumpsteer fix I came up with for the pre 88?

I drew it up quick in solid works, I'm not sure how thick the metal piece would have to be and you would have to grind a new notch in the rod part of the balljoint to fit the plate in between it and the knuckle, but this would allow you to use the stock A arm and attach the tierod at the same level as the A arm and have it be the same length. You would have to mount the tie rod next to the A arm on the cradle. This would be easy to make and cheap too and fully get rid of the rear bumpsteer. It would also be way lighter than the held system.



zkhennings MSG #282, 01-31-2012 02:19 PM
      Also it probably doesn't even need all the material I put on there. Nothing is actual dimensions, When I have the chance when I go home I will measure everything out. the tie rod could also be attached right to the A arm if a bracket was welded on. If a tri link system like on the 88 was desired so that the suspension toes in when compressed or when drooping, then the metal piece on the bottom could just be extended to the left side of the knuckle and another link could be attached there and go to the frame which would just aid the bushings during torque steering. And, it would be an improvement over the 88 because the link being attached underneath the knuckle causes the wheel to gain positive camber when turning hard, so being attached at the same level as the A arm would be ideal. I am going to do this to my own car when I can, what do you guys think?

zkhennings MSG #283, 01-31-2012 09:32 PM
      Do you guys think any more bracing would need to be added? like a triangular member perpendicular to both existing members for added stiffness?



And here is what I mean with the balljoint, the bit cut away on the right is the original slot and the slot to the right is the slot that would have to be made however far up from the old slot that the metal piece is thick. Then it would have to be spun around to the other side (obviously)

[This message has been edited by zkhennings (edited 01-31-2012).]

FieroWannaBe (patond@alumni.msoe.edu) MSG #284, 02-01-2012 07:44 AM
      Dont modify ball joints, replacements are cheap pieces of crap, and when one fails on the road, you don't want to modify a new one, I would trim the upright down. But to add, I think the lower plate is a little thin where it attaches to the knuckle, the whole structure reduces to a small cross section there, and your bending moment would be highest there.

zkhennings MSG #285, 02-01-2012 10:29 AM
      trim the upright? if I did that I would want to weld the plate to the bottom of the upright to make up for the lost material, is the upright weldable? and If you think that it will be ~.25 thick steel then I dont think that it will be much of an issue because if you think about how the tierod end will only apply force parallel to the surface of the plate, so a torque will be applied around the original attachment of the tierod end and then the steel oposing that torque is at least 1 inch wide which translates to one inch thick. and I think that the hole where the tie rod end used to attach will be what takes care of most of the bending forces in the direction that the steel is weak

[This message has been edited by zkhennings (edited 02-01-2012).]

fieroguru MSG #286, 02-04-2012 02:59 PM
      Been playing around with lowering the pickup locations for the 88 lateral and trailing links:




When the girls get up from nap, I will be time to cut some steel.


fieroguru MSG #287, 02-04-2012 07:23 PM
      Almost done...






Tha Driver MSG #288, 02-04-2012 08:52 PM
      Nice. Have you checked wheel clearance (will that work with 15s)? And of course you have tubes to go between the brackets where the long bolt goes...
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts


fieroguru MSG #289, 02-05-2012 07:26 AM
     
 
quote
Originally posted by Tha Driver:

Nice. Have you checked wheel clearance (will that work with 15s)? And of course you have tubes to go between the brackets where the long bolt goes...
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts


Here are the pics from a test fit to a 16x7 wheel. There is a chance it could clear a stock wheel, Once I have it tacked together, I can pull out a stock wheel and test it.



The sleeve for the long bolt has been on order, just not here yet. There is also 1 more part to make that will bolt to the backside of the trailing link attachment. Like I said "Almost" done.

[This message has been edited by fieroguru (edited 02-05-2012).]

Bloozberry MSG #290, 02-05-2012 07:31 AM
      Here he goes again with another new fangled idea. Would you please slow down... you're making the rest of us look bad.

ricreatr MSG #291, 02-05-2012 01:50 PM
      simply beautiful

fieroguru MSG #292, 02-06-2012 07:35 AM
     
 
quote
Originally posted by Tha Driver:

Nice. Have you checked wheel clearance (will that work with 15s)?
~ Paul
aka "Tha Driver"

Custom Fiberglass Parts


I checked last night and with the reinforcing braces coming in from the back side, it will not clear a 14, 15 or 16" wheel. To clear these wheels, the extension to the trailing link would need to be cantilevered beyond the stock location with the side bracing coming in directly across from the bolts (vs. being angled to support the extended end directly). However, it would probably require a thicker piece than the 3/8" that I am using and there still might not be room for the head of the bolt.

You need to run 18's on the 88 to clear the top of the upright/strut mount anyway, so my main priority was to design them to clear some deep 18 (which is also why the trailing link attachment is shifted inboard 3/8" and still might get a small spacer in the 1/2" - 3/4" range to help the wheel clear the trailing link

Here is a 17" wheel - notice that the strut mounting section restricts the backspacing of the wheel:


Here is an 18" - where the wheel can cross over the top of the strut mounting allowing for an extra inch of backspacing:




Austrian Import (maximilian_ledworowski@csumb.edu) MSG #293, 02-06-2012 09:19 PM
      Cool. Can you play around with it and see if you can somehow fit an upper A-Arm in the back?

Something like this maybe:


fieroguru MSG #294, 02-06-2012 10:00 PM
     
 
quote
Originally posted by Austrian Import:

Cool. Can you play around with it and see if you can somehow fit an upper A-Arm in the back?


Upper a-arm in the rear really is of no interest to me.
There is only about 4 1/2" between the frame rail and strut bolts, and that is before I pull the strut in another inch to maximize the wheel size under a stock bodied fiero. That would leave the upper a-arm about 3 1/2" in length, or I would have to hack into the frame rail...


spearce (spearce52@rogers.com) MSG #295, 02-07-2012 08:57 AM
      I found this while snooping at the local auto salvage yard. It might be useful in trying to make a rear SLA suspension. Its found on 94-97 Cadillacs



Steve


Will (william.lucke@gmail.com) MSG #296, 02-07-2012 03:57 PM
     
 
quote
Originally posted by fieroguru:



This looks like it's only about 1/4 of interference, but would probably reduce max possible wheel width by 1/2" to assure adequate clearance.

"Just" build a bent/cantilevered trailing arm.

I have a Percy's Wheel-Rite also.


fieroguru MSG #297, 02-08-2012 06:13 PM
     
 
quote
Originally posted by Will:
This looks like it's only about 1/4 of interference, but would probably reduce max possible wheel width by 1/2" to assure adequate clearance.

"Just" build a bent/cantilevered trailing arm.

I have a Percy's Wheel-Rite also.


The clearance to the trailing link will be one of the easier things to "fix"
The Percy's tool is pretty handy. Been thinking about making one out of steel so it is more precise.


fieroguru MSG #298, 02-08-2012 06:16 PM
      The sleeve material came in, so I went ahead and welded one side up:



It even comes off:




Mocked up:



Bloozberry MSG #299, 02-08-2012 08:40 PM
      I think this is great exploratory work fieroguru, but I would like to point out what appears to me to be a weakness. Perhaps it's only an illusion given the angles of the photos, but the area pointed out in the picture below seems to be quite small in cross section. All of the accelerative and braking forces are going to be transmitted from the wheel to the lower of the two holes in your bracket where the trailing link is now attached. This is going to create a moment about the upper hole in your bracket that is now used to attach the bottom of your bracket to the old trailing link hole in the knuckle. The only thing that appears to counter this moment is this small area pointed out in the photo. It seems to me that the area pointed out in the photo will bend as the trailing link tries to pivot the piece of steel that it's mounted to, about the upper hole. (I did my best to explain it, but I know it may not be clear.)



fieroguru MSG #300, 02-08-2012 09:59 PM
      That area would be a weakness if that was the only attachment. The other side of the trailing link extension is welded along the full length (on both sides) and the backing plate is also there to help spread the loads and act as a reinforcement.

The other factor at play is the side with the notch, is in a plane about 3/4" from the centerline between the two trailing link bolts, so it will not be very effective in resisting the acceleration loads that will want to rotate the 3/8" piece backwards. The plate on the other side angles back and attaches to the upright in a plane that is about 3 3/8" from the centerline between the two trailing link bolt, so it is much better suited to resist the acceleration loads. The backing plate also ties into this rear plate to help spread the loads. The only reason I put the front plate on, was to help stabilize the extended portion of the 3/8" plate and to keep the lower edge from twisting since the trailing link is cantilevered off to the side.

[This message has been edited by fieroguru (edited 02-09-2012).]

fieroguru MSG #301, 02-09-2012 07:08 PM
      Here are some quick mockups. I did shim the wheel about 3/8" outboard to clear the new lateral link bracket on a 16" wheel.

With 6 1/2" between cradle and floor (1/4" higher than stock ride height specified in Bloozberry's drawings) or 28" to center of wheel well opening:


Stock (lateral links are almost level):


With fieroguru lateral link relocation (lateral links angle down, will kick out the bottom of the tire for positive camber gain under compression):


With 5" between cradle and floor (1 1/4" lower than stock ride height) or 26.5" to center of wheel well opening:
Stock (lateral links already pointing up to the wheels)

With fieroguru lateral link relocation (lateral links close to level again - restores to stock suspension geometry with 1 1/2" lowering):


With 3 1/2" between cradle and floor (2 3/4" lower than stock ride height) or 25.0" to center of wheel well opening:


Stock (significant negative camber gain... definitely not good)


With fieroguru lateral link relocation (less bad - pretty much the same as the stock suspension lowered 1 1/2"):


I am planning to start a separate thread specific to this lateral link relocation.


zkhennings MSG #302, 02-11-2012 01:29 AM
      Which tire has more grip in a turn, inside or outside tire? (Trying to decide if the camber curve on droop is more important than compression)

LZeppelin513 (bjamestate@gmail.com) MSG #303, 02-11-2012 05:37 AM
     
 
quote
Originally posted by zkhennings:

Which tire has more grip in a turn, inside or outside tire? (Trying to decide if the camber curve on droop is more important than compression)


weight transfers to outside tire


Will (william.lucke@gmail.com) MSG #304, 02-12-2012 10:55 AM
      Umm... depends on your definition of "grip". The textbook definition of "grip" is the ratio of normal force to the lateral force that a tire can take. With that definition, the inside tire has the most grip.

However, because most of the car's weight is on the outside tires, they are responsible for the vast majority of the lateral force that makes the car turn.


Will (william.lucke@gmail.com) MSG #305, 02-12-2012 10:57 AM
     
 
quote
Originally posted by fieroguru:

The sleeve material came in, so I went ahead and welded one side up:



This is a really nifty idea; it's a really cool way to package the improved geometry.

I have different ideas about the bigger bearing in the '88 knuckle, though...


Bloozberry MSG #306, 02-12-2012 12:26 PM
     
 
quote
Originally posted by Will:
I have different ideas about the bigger bearing in the '88 knuckle, though...


Quit holding your cards so close to your chest... share some of your ideas.



Will (william.lucke@gmail.com) MSG #307, 02-12-2012 12:33 PM
      Wholesale, not piecemeal...

ricreatr MSG #308, 02-15-2012 09:54 AM
      Like austrianimport, i have been bitten hard by the "double wishbone rear suspension" bug.
guru's huge contribution with the lowered pivots, is still sinking in,
and blooze's magnificant draftings have me scribbling at a furious rate.
then i bumped into more lamborghini pictures . . .

my drawings stink, so . . .

please let me know if the geometry is as good as i think it might be, and where i really screwed things up.

it starts with guru's lowered pivots bracket, but the front pivot gets changed to a ball joint. the trainling link pivot on the bottom of the knuckle is eliminated and instead the trailing link gets fused to the forward lateral link very near the joint at the knuckle.
similar to this drawing, but only involving the forward pivot/link, and the forward link's mount.
Originally posted by aaron88


the forward pivot would be kept at ~4.5" (or more) higher than the others to maintain anti-squat, and continue to use rubber.
the rear link stays the same, and is soley used to set toe.
i would prefer to use tie rod ends where the heims are being used. i think they will last 10x longer, cost the same, and still be rigid.

next we construct an adapter for the top of the knuckle similar the the adapter on the bottom (using the strut bolt holes). this adapter places a pivot ~2" outboad of the knuckle/strut bolts. it provides a place to mount a triangular arm just like the lower one.
it's forward mount would also be ~4.5" higher to maintain anti-squat? and end up just about on the firewall. (also in rubber)
it's outboard mount would be a ball joint as well (to take accel/decel forces)
it's inboard mount would be a tie rod end, and as you know the real trick is where to mount it.
using blooze's drawings (thanks again is not enough). i calculate that we can keep the arm parallel with the lower one. and give it a length 2/3 as long as the lower arm. is 2/3 length good? it is very close to the ratio/angles of a late model chevy pickup i was just looking at. this length places the pivot just inside the upper frame rail and partially through the top of the frame rail. i have drawn a braket for the top of the frame rail that includes reinforcemnt around the cuts, and a top half to the pocket cut out for the arm to pass through.
there would be no need for a rear lateral link on the top ./?



rear scrub radius.
i may be way off here, but it appears the stock rear scrub radius lands at about the inboard edge of the tire. (using the top of the strut as the upper pivot and the middle of the trailing link at the knuckle as the lower pivot.) i know the lateral links take up all the force, so it will not affect steering, but 400hp pushing 2500 pounds seems like a lot of "turning" force applied to the lateral links.
this revised suspension uses upper knuckle adapter pivot for the upper scrub point, and the lower knuckle adapter pivot for the lower scrub point. the effect is to move the scrub radius very close to the middle of the tire. improvement?

i have this all laid out on the graph paper, and it looks good to me, but this might help a lot.


aventador underside arrow is pointing to the rear. (alot better than my drawings ehh!)
it appears to me that the forward mount is raised significantly from the others.
the rear link is similar to fiero. the front wishbone replaces the forward lateral link and the trailing link.
here is a top view obscuring the rear link, but on the lower arm shows the front mount being higher, and notice the upper arm, different from the proposed design, but the its mounts are cut into the upper frame rail similar to what i had envisioned.

more/larger pics here http://blogs.insideline.com...sion-walkaround.html

if you are still listening after the frame rail discussion, then lets move on to the other big hurdle to double wishbone (type) conversion . . . carring the weight.
i would propose a cantilevered inboard coil over design.
in the vacant spot left by removing the upper rear lateral link, use a member similar to the omitted link, but longer and with three pivots. the outboard pivot would be located on the upper knuckle bracket 4" behind the ball joint used for the upper control arm's outboard joint. the middle pivot is on top of the frame rail 5" behind the other frame rail pivot. and the inboard pivot would be in the engine compartment more or less straight up from the spot on the cradle where the lower rear lateral link attatches.
the inboard pivot is used to attatch to a coil over shock. the body of the shock is vertical. mounted low on the cradle at this spot again .
in this shot the shock would go on the right side of the picture, just behind the cv joint. (remember his bracket sits higher than normal)
Originally posted by bse53:


the shock is right side up, has lower center of gravity, and has reduced unsprung weight. its length would be about 14", and only need ~3" travel. the height adjusters are easy to get to as well.
the cantilever link would be parralel with the upper control arms rear bar, until it hits the second pivot, then it would bend up towards the sky at a ~45* angle. this geometry should give increased spring rate with suspension compression.
it would require roughly double spring rate because of the leverage.
room? - there is plenty of room on the drivers side!, but on the pass side my alternator is in the way (3800 conversion.) i will gladly move it.
i can see the middle pivot binding. it would require a sliding roller.?



after thinking last night, i wonder if the upper arm could carry all of the anti squat (acel) and the lower arm could be left level. this would give anti dive to the rear under braking?

so gentlemen, here is hours of my time. maybe number the critisisms so we can keep track of them all!?

[This message has been edited by ricreatr (edited 02-15-2012).]

sspeedstreet (sspeedstreet@verizon.net) MSG #309, 02-15-2012 01:58 PM
      I like the concept. Taken a little further:



ricreatr MSG #310, 02-15-2012 04:48 PM
      i like.
includes eliminating the toe link on the lower plane?

it would take away the 88 feature of seperating the transverse forces from the longitudinal forces though . . . hmm

[This message has been edited by ricreatr (edited 02-15-2012).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #311, 02-15-2012 06:42 PM
     
 
quote
Originally posted by ricreatr:
Like austrianimport, i have been bitten hard by the "double wishbone rear suspension" bug.


Glad I'm not the only one bitten by the bug. I was starting to worry I was the only one.

[This message has been edited by Austrian Import (edited 02-15-2012).]

zkhennings MSG #312, 02-15-2012 09:00 PM
      I think If a double wishbone setup were done then either a bracket should be welded to the bottom of the strut hat to attach a coil over and then it could attach at the top of the knuckle via bracket.

And one question... say the car rolls 3 degrees in a turn... do you assume that the wheel on the inside has dropped the same amount as the wheel on the outside has compressed? ie they are at the same angle to the ground as the car is without any correction from the suspension?


ricreatr MSG #313, 02-23-2012 05:01 PM
     
 
quote
Originally posted by Will:

I have different ideas about the bigger bearing in the '88 knuckle, though...


 
quote
Originally posted by Bloozberry:


Quit holding your cards so close to your chest... share some of your ideas.


Will hasn't got any cards . . . he hasn't got any game . . . he hasn't got any (good) ideas,
or he would have shown them to us allready!

.

You have been called out!


Will (william.lucke@gmail.com) MSG #314, 02-24-2012 04:41 PM
      If you design and build 16 parts to improve a suspension, what have you gained over a clean sheet design with 12 parts?

wftb (danjesso@bmts.com) MSG #315, 02-24-2012 07:17 PM
      one thing you should get rid of if you go to a upper A arm on an 88 suspension is the trailing arm .it just is not needed with an unequal length upper and lower A arm suspension . make the lower arm one piece with adjusting bits and problem solved .i think the aventador suspension is way more complicated than a fiero suspension needs to be .more weight , more horse power wider wheels and people that pay a lot of money for a car wont even accept tubular steel arms any more .even a vette has aluminum arms .

ricreatr MSG #316, 02-25-2012 12:24 AM
      foooey! thought maybe i could twist your arm to give up what you have in your head. cant blame me for trying.

excellent point, a clean sheet design sounds great, but i wouldnt know how to start a project like that.


wftb, no trailing link sounds good to me, but i have talked to a couple people that like the fact that all of the forward motion of the car is in one link that can have rubber bushings (to help with wheel hop), and the laterals can have hard/precise joints for steering.
me . . . i dont know.

i like aluminum . . .

[This message has been edited by ricreatr (edited 02-26-2012).]

Will (william.lucke@gmail.com) MSG #317, 02-25-2012 08:24 PM
      The trailing arm bushings contribute to wheel hop because they allow torque to put load into the suspension in a direction that's not specifically damped.

ricreatr MSG #318, 03-01-2012 04:13 PM
      soo, too complicated (and no other responses).

this awsome thread had me thinking something simpler.

 
quote
Originally posted by 88lambo:




what about leaving the guru lower mod in place. using the big 18" wheels, and drilling/tapping the knuckle for a large heim such as the drawing?

the upper arm is 19cm (7 1/2") long, compared to the lower that is 31cm (12 1/4"). this keeps an upper to lower ratio of 62%. very close to the ratio of the front arms.
i think i would use more suspension drop (2" total). the drop would make the lower arm higher than level at the knuckle. the upper arm gets steeper down.

is the geometry any good? i can see camber out on an inside tire, and a good bit of camber in on the outside tire.

is this enough info to run it through a program?



edit: should work with early cars too.

[This message has been edited by ricreatr (edited 03-01-2012).]

Bloozberry MSG #319, 03-01-2012 05:03 PM
      Three observations:

1. I'm not sure that you could get away with drilling and tapping the upper part of the knuckle since the threads of the heim joint would place the casting under tension. You would need to drill right through and use a hardened nut on the backside to avoid the problems of relying on the porous casting.

2. Where do you plan to attach the coilover/shock/strut to the arms/knuckle?

3. I understand that the geometry needs to be worked out first and foremost, but something you should keep in the back of your mind is that the lower frame rail is fabricated from two 18 ga stamped steel Z sections spot welded together along the flanges. You would want to consider the loads and how they will be applied to this type of frame especially after you've cut into it to fabricate your pocket mounts.

Edit to add:

4. the lower frame rail isn't parallel to the centerline of the car when viewed from the top as you've sketched. In fact, it's wider at the front and narrows towards the back considerably. There is approximately a 110 mm difference in the width between the LH and RH lower frame rails where you've proposed the forward and aft mounts for the upper control arm (dimensions taken from inside the engine bay). This might complicate locating your mounts.

[This message has been edited by Bloozberry (edited 03-01-2012).]

Will (william.lucke@gmail.com) MSG #320, 03-02-2012 10:41 AM
     
 
quote
Originally posted by Bloozberry:

2. Where do you plan to attach the coilover/shock/strut to the arms/knuckle?


The way he's depicted it, the load on the rod end would be in compression rather than tension (at least on the outside wheel)

What's pictured is essentially the first avenue I considered for improving the Fiero rear suspension.
The intelligent way to make that work is to fab a bracket (can be *VERY* simple--two plates with 4 holes each) that would be secured to the knuckle via the stock strut bolts. The bracket would connect to the outer pivot of the upper control arm outboard of the stock strut mount, while providing a location inboard of the stock knuckle to bolt the lower pivot of a coil over assembly. Obviously this would be used in conjunction with an upper coil over shock mount that would bolt into the stock strut tower bolts.

 
quote

3. I understand that the geometry needs to be worked out first and foremost, but something you should keep in the back of your mind is that the lower frame rail is fabricated from two 18 ga stamped steel Z sections spot welded together along the flanges. You would want to consider the loads and how they will be applied to this type of frame especially after you've cut into it to fabricate your pocket mounts.


Also keep in mind that a large fraction of the lateral suspension loads on the cradle go through the lower frame rails via the rear cradle mounts. As well there is a component of the vertical load of the suspension delivered to the lower rail by virtue of the fact that the strut tower is connected to the lower rail.

IOW, the lower rail is far from being tissue paper... However, to properly support an UCA, some insightful design of the pivot locations would be necessary in order to fully tie them in to the rail.

[This message has been edited by Will (edited 03-02-2012).]

Datsun1973 (akmeudt@gmail.com) MSG #321, 03-02-2012 07:15 PM
      I'll try to get some pictures up but I have converted my 88' rear suspension to a full SLA. The car is still in my trailer after the move so it may be a bit.

The two lower transverse links are stock. I used urethane bushings in them. The lower pivot point was machined to accept a 5/8" hiem. The cradle point, same. The lower long lateral link is now a basic sprint car threaded tube with a heim on either end. The upper mount is a little bit more complex. I made two plates that sandwich where the strut would attach. Those plates look something like an "L." This is where the push rod attaches to actuate the coil-over. Some will ask why this point and the key is load path. By attaching the spring/shock to the upper part of the hub carrier you run the load through the path the OEM engineers intended. Attaching to the lower link is not a good idea because you induce bending loads where they were never meant to be (although I think the lower link is beefy enough to handle it). The upper arm is again made of 5/8" heim joints for the transverse link that runs from the lower of the two holes and to the upper frame rail. A second upper lateral link runs forward from the front side of the carrier to the upper frame rail. In the end you essentially have a SLA that is infinately adjustable with good camber gain. The roll center and momment also appear to be fairly good as well.

The coil-overs are mounted on the upper frame rail horizontally orientated front to back. They are actuated through a machined rocker that rides on ball bearings.

This type of setup may or may not work in a stock fiero. My car has a tube frame that uses Fiero underpinnings.



Bloozberry MSG #322, 03-02-2012 08:51 PM
      Where have you been all this time! If you have the three dimensional spacial coordinates of the upper control arm pivots (referenced to some other known stock point) as well as those for the shock, the kinematics can be mapped out to show the advantages. I've posted the stock coordinates elsewhere so only the changes would be needed. Pics would be great, but data is even better.

ricreatr MSG #323, 03-02-2012 09:14 PM
      ALLRIGHTY THEN!!!!!!

this is gonna be good. i can wait for THOSE pictures!!
are you the one they made the rule exception for???
(maybe a hand drawing to tide us over in the mean time)

side note: the last sketch i did of the simple upper arm has poor choice of heim in the knuckle. accel/decel forces would work to push the ball out of its socket, so it will not work as is. would need a ball joint of some sort installed with a bracket.



Austrian Import (maximilian_ledworowski@csumb.edu) MSG #324, 03-07-2012 04:17 PM
      can't wait.

Datsun1973 (akmeudt@gmail.com) MSG #325, 03-07-2012 04:31 PM
     

Yes that is an LZ4 running with the OEM computer and harness. VVT and all is functioning. VATS, rear O2 and other sensors were deleted with HP Tuners.

[This message has been edited by Datsun1973 (edited 03-07-2012).]

Jefrysuko MSG #326, 03-07-2012 07:05 PM
     
 
quote
Pictures posted by Datsun1973:



That's really cool. Do you have a sway bar hidden in there somewhere?


Datsun1973 (akmeudt@gmail.com) MSG #327, 03-07-2012 07:35 PM
      Thanks. No sway bar yet but there is room to add one later if needed. I subscribe to the Carol Smith design school (Tune to Win, Engineer to Win, etc) books. Sway bars are band aids for bad designs. I am sure folks on here will dispute me on that but Carol is the man.

ricreatr MSG #328, 03-08-2012 12:11 AM
      THAT IS ABSOLUTELY AWESOME!!

thanks for posting pics soon.

do you have about 4" total travel?
these seem to be pics from a while ago, so it might not be possible, but can you get a pic of the shock absorber rocker from a straight on angle? (have been playing around with pushrod sketches, and dont really know what i am doing)
have you had it on the road/track yet?

thanks again!


Datsun1973 (akmeudt@gmail.com) MSG #329, 03-08-2012 05:03 PM
      Travel is around 4" I think. This car was designed as a road course machine with limited emphisis on travel and more on roll control and maximum tire contact patch.

Actually the picture with the engine is from last summer when I was doing the initial engine wiring and first start. The basic frame is about 2 years ago.

The car is in storage so actual pictures will be difficult right now. As for rocker arms I didn't change the motion ratio and just used a simple 1:1 ratio. The easiest way to design a rocker is pick your shock location and rocker point. Using a circle with the rocker pivot as the center of that circle you can pick two points for the ends of the rocker. I would recomend the Carol Smith books, Tune to Win and Engineer to Win. He outlines some basics for suspension design and goes over things like mountings in double shear, load paths, what metals to use, etc etc. Great read. Unless you NEED an inboard or remote mounted shock/spring there is no performance benefit to this setup for a common road car. I did it because I couldn't figure out a way to mount a QA1 large body shock and spring outboard with the corvette wheels and 305 series tires. In board shocks/springs also reduce unsprung weight and allow a greater number of motion ratios, again not a player for a common road car. You also need to consider cost. Those rockers were CNC machined out of billet 7075 and the heim's are top quality chrome-moly units from AED motorsports.

A better alternative for a stockish fiero is Fieroguru's post on relocating the strut inboard. Hopefully he will make a kit similar to his link relocation kit.

The car does drive, but has only been into and out of the trailer. I am working on the shift cables to the F23 right now. The shift cable doesn't have enough throw so I need to trim down the jacket material and see if I can get an additional 1/2" of throw.


Bloozberry MSG #330, 03-08-2012 06:37 PM
      Very clean looking design. Do you have any data or graphs showing the kinematic performance of camber, toe, and roll center in bump and roll?

fieroguru MSG #331, 03-08-2012 07:29 PM
     
 
quote
Originally posted by Datsun1973:





That is pretty cool!


Datsun1973 (akmeudt@gmail.com) MSG #332, 03-08-2012 07:31 PM
      Yes and No. I did the design using scale "paper dolls" and push pins to check the dynamics. When I did the Formula SAE cars in college I had several software packages that accomplished the same thing. I will try to get measurements once the car gets home and you can map it out. I am curious to see how close I got. However, with any suspension design it's always a compromise between roll center, roll momment, anti-squat, and packaging. I would have preferred the lower and upper arms to be longer but with the transverse mounted engine/trans this is very difficult to package.

I thought you'd get a kick out of this too:



[This message has been edited by Datsun1973 (edited 03-08-2012).]

Datsun1973 (akmeudt@gmail.com) MSG #333, 03-08-2012 07:35 PM
      Thanks guru!

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #334, 03-13-2012 04:07 PM
     
 
quote
Originally posted by Datsun1973:

Thanks. No sway bar yet but there is room to add one later if needed. I subscribe to the Carol Smith design school (Tune to Win, Engineer to Win, etc) books. Sway bars are band aids for bad designs. I am sure folks on here will dispute me on that but Carol is the man.


Sway bars are band aids. Have you seen the suspension setup on the McLaren MP4-12c? They completely did away with sway bars and replaced it with hydraulics.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #335, 03-13-2012 04:17 PM
     
 
quote
Originally posted by Datsun1973:








That setup is even better looking that what I envisioned when I started this thread. Please post more pictures and info. If something like this could be adapted to the Fiero, that would be awesome.

A pushrod suspension like this on the front would look gorgeous as well.

Unsprung weight matters on street cars as well. (just not as dramatic). Going from 14" rims+tires at 35lbs total to 18" rims+tires at 49lbs total, I could totally tell the handling difference, turn in response, etc. Adapted from Colin Chapman I believe, "weight does not like to change direction".



Austrian Import (maximilian_ledworowski@csumb.edu) MSG #336, 03-16-2012 01:31 AM
      Datsun1973, is there a build thread on any forum about this car?


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #337, 03-16-2012 01:57 AM
      *double post*

[This message has been edited by Austrian Import (edited 03-16-2012).]

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #338, 03-16-2012 02:21 AM
      This is another approach:




http://www.rx7club.com/show...9401318&postcount=11


or a setup like this with a longitudinal Subaru/Porsche boxer engine.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #339, 07-06-2012 02:35 AM
      bump for updates

el_roy1985 MSG #340, 08-28-2012 09:20 PM
      Sick suspension setup. After looking at Lambos and such, this is the approach I had planned to take in the future. Nice to see someone actually did it, and it also gives me a lot of insight on how to go about mine in the future.

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #341, 10-24-2012 07:27 PM
      http://www.martinwhite.name.../88cradle/index.html using this to bump the thread.

Can't wait to see more designs with double wishbone, or multi-link rears.


Ang84Indy MSG #342, 10-25-2012 10:02 PM
      This is a very informative thread! Thanks to all who have contributed. I have a question: A while back there was a discussion about staggered tire/wheel widths. When going to a larger width rear wheel, is there a formula to figure proper size, or does one just guess?

fieroguru MSG #343, 10-26-2012 06:20 AM
     
 
quote
Originally posted by Ang84Indy:

This is a very informative thread! Thanks to all who have contributed. I have a question: A while back there was a discussion about staggered tire/wheel widths. When going to a larger width rear wheel, is there a formula to figure proper size, or does one just guess?


Section width variation front/rear should be close to the weight bias front/rear.
So if your car is 46%(F) / 54%(rear) you could run 205's in front and 240's in the rear or 215/250 or 225/265 or 235/275



Boostdreamer (thinner00@hotmail.com) MSG #344, 10-26-2012 09:52 AM
      @Datsun1973, what is the spring rate on your rear coilovers? I would expect that they would need to be really soft in that configuration.

Jonathan


Ang84Indy MSG #345, 10-26-2012 12:22 PM
      Thanks Fieroguru!

daveheld (dheld@cfl.rr.com) MSG #346, 11-12-2012 07:44 PM
      here's another option... and it's for sale.

dave
Cocoa Beach FL







IVANNATINKLE (seanmiller063@gmail.com) MSG #347, 11-12-2012 11:46 PM
      how does it attatch to the fiero?

IVANNATINKLE (seanmiller063@gmail.com) MSG #348, 11-19-2012 12:28 AM
      What about something like this http://www.xj40.com/viewtop...c030dcd3eaa&start=30 ?

aaron88 MSG #349, 11-24-2012 12:25 PM
      Does anyone know of a rear knuckle similar to the Fiero 88 one?

As it turns out it was a lot easier to figure out how to correct the rear geometry than it is turning out to be to figure out how to do it cheaper than a complete custom job (about $4500). I have my cradle built and the lower control arms designed but my hang up is figuring out how to make it connect with the 84-87 rear knuckle without making a custom knuckle. Every solution I come up with drives the cost up. All the solutions that I have come up with are not rigid enough, or have transitions with high stress concentration points.

So I'm wondering if there is something out there that can be slightly modified to work. But by my lack of ability to locate one by now makes me assume that there is none. I will probably have to design and make custom rear knuckles (which would solve the bearing, caliper, strut mount and ball joint problems), but obviously drive the price up.

My lower control arm design is still as posted previous (and below).


Cradle design below.


.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #350, 01-23-2013 01:40 PM
      bump in hopes of new contribution

Will (william.lucke@gmail.com) MSG #351, 01-23-2013 02:24 PM
     
 
quote
Originally posted by daveheld:

here's another option... and it's for sale.

dave
Cocoa Beach FL




Why is the cradle attached so close to the center instead of on a wider mount center? That must compromise the torsional stiffness of the interface significantly.


aaron88 MSG #352, 01-23-2013 10:28 PM
      Going to be made soon. For an 86 but using a Blazer bearing, Corvette brakes and relocated strut mount to clear wider tires.



Slow but progress is ongoing.


Will (william.lucke@gmail.com) MSG #353, 01-24-2013 09:52 AM
      What sort of control arm are you going to attach to it?

Yarmouth Fiero (im_gman@hotmail.com) MSG #354, 01-24-2013 09:59 AM
      Great job aaron88. Are you using ProEngineer, Inventor, Rhino.......Sorry, I didn't notice if you mentioned earlier in the thread.
Will the part be billet and cnc'd or fab'd or a combination? Its a pretty complicated part.


lateFormula MSG #355, 01-24-2013 11:44 AM
      Looks like SolidWorks to me...

aaron88 MSG #356, 01-24-2013 11:36 PM
      Yes, it's SolidWorks 2005. I can't afford to upgrade it. But at least it has FEA as well built in.

The main parts are going to be cut on a water jet then welded together. I guess it only seems complicated because I wanted a lot of functionality out of the design. There is no left or right until I machine the main part. Bearing choice is optional between Fiero, S10 Blazer or whatever else you could want. Brake mounting point is completely adjustable and ball joint mounts are part of the main body. Strut mount is adjustable for wider tires. Then I cut out some of the open areas to lower the weight. No skin off my back as there is no additional cost for any of that. Same design can be used for all years, I just have to move the strut mount over for the 88's. CNC is way too expensive for me since I don't have one.

Control arm is the same design as shown above. I'll add a shot of the assembly drawing shortly.

.


Austrian Import (maximilian_ledworowski@csumb.edu) MSG #357, 01-25-2013 02:51 PM
      Aaron, do you want to do a double wishbone design as well, or just a strut?

aaron88 MSG #358, 01-25-2013 05:04 PM
      I did look at doing double wishbone and ultimately it was way too expensive. Plus I would only be able to do it in-house. The Fiero would have to be brought to me since I would have to make pockets in the frame. So if anyone want's to go that far, for the same price you could probably back half the car, assuming the engineering was already done. And if your going to back half the car you might as well whole the car (tube frame). My thoughts anyway.

zkhennings MSG #359, 02-04-2013 03:08 AM
      I think I have an actually good idea regarding improving the geometry of the pre 88 rear suspension. I will cad something tomorrow, I don't have cad on my laptop right now as I reinstalled windows, but I will try and explain my idea. Essentially have rectangular tubing in an L shape, and it bolts where the factory control arms bolt into the cradle, and it can either be welded in at that point to the cradle or have extra bolts attaching it from the top and bottom of the cradle. Every L shaped piece of rectangular tubing would fit nicely in the opening on the cradle, and all 4 would be the same size. Then there would be holes in the now raised portion or the L that would allow the control arms to be relocated higher up which would help if the car was lowered, and it helps camber gain. The stock control arms would probably not be able to be used. The hole that the control arms would mount to could also be slotted vertically to play with different angles of control arm at ride height, and testing could be done while measuring tire temperature to see where the optimal geometry was. I am willing to try this out on my car, so I understand the forces on the L shaped pieces will cause it to torque under braking or acceleration, not really worried about cornering forces. How thick do you think the steel should be? Construction for each L would be a 4 piece deal with two flat L shaped pieces water jetted, and then two rectangular pieces that would be bent at 90 or however many degrees is appropriate because it does not need to be a right angle L. Then all 4 pieces would be welded together. It would be plenty strong, I think it is a pretty good idea. Now the harmonic balancer/ pulley wont get in the way of just raising the control arm mounts on the cradle.



The only real forces the control arms exert on the bolts are either a pulling or pushing force/ a torquing force too, but no forces in the up or down directions. So the L shaped steel would just have to be strong enough to not buckle under cornering loads. A car pulling a 1g turn weighing 2700 pounds (~1200Kg) would have to have a total force of around 12000N at the wheels. Even when assuming that one wheel is providing all of that force, steel has a yield strength of 248 MPa or 248000000N/m2. Shear stress of quarter inch steel 2 inches in length parallel to shear force for cornering times two for the two pieces of metal that would be the bracket means that (2)*(.0254)*(.25)*(.0254)*(248000000)*(2) = 160,000 N is required to shear that bracket. And quarter inch steel would be overkill

[This message has been edited by zkhennings (edited 02-04-2013).]

aaron88 MSG #360, 02-10-2013 04:09 PM
      Assembly drawing sketch showing control arm.



.


Will (william.lucke@gmail.com) MSG #361, 02-10-2013 04:45 PM
      Ball joints, not spherical bearings?

aaron88 MSG #362, 02-10-2013 07:42 PM
      That's right, ball joints and tie rod ends. It was part of my design criteria. All components that move or wear are direct unmodified common parts that can be picked up in any automotive supply store. And should be in stock there not special order.

Wops...let me make a correction, that should read "most components". Some of the components for the front end have to be picked up at the dealer.

Aaron

.


aaron88 MSG #363, 04-20-2013 04:45 PM
      I have done another design using poly mounts. I like this design better but it doesn't allow for quick bushing replacement unless you have stock on hand. These use universal pivot bushings. I think this is the one I'm going to built onto the cradle I have already made.

The front arm comes out that far to clear the transmission on the other side.




Also notable is that I'm going to design and possibly build an upper control arm to use with the stock slightly modified shock.

.


Will (william.lucke@gmail.com) MSG #364, 04-22-2013 08:45 AM
      While I sympathize with your thoughts that the right commonly used ball joints will be readily available locally...

Spherical bearings are going to be just as easy to find as urethane bushings, both of which will most likely be mail order.

Of the two, I'd pick spherical bearings over urethane any day of the week. The geometry will be more consistent, motion will be quieter, service life will be longer (especially if sealed spherical are used with additional external seals) and replacement will be easier.

Strut suspensions tend to work well when the inner pivots of the control arms are higher than the outer pivots.
SLA suspensions tend to work well when the inner pivots of the lower control arms are level to or lower than the outer pivots.


aaron88 MSG #365, 04-22-2013 09:47 AM
      Will;

Maybe you can help me locate long life spherical bearings. I know that you have looked into it. As far as I know nobody is guaranteeing more than 10 000 km life. I'm looking for a selection of two bearings, one premium and one economy (or value/$). I have looked around but can't really find any information on the life of the bearings. I know the poly is cheep and lasts a long time between service. What do you have against poly on the inside and spherical bearing on the outside? Should make for a slightly smoother ride, and because the control arm pivots are so far apart it shouldn't affect the toe if it's only on the inside. I found these weld cups that you linked in another thread somewhere, but I'm confused about the brand of bearing to use:

http://secure.chassisshop.com/partlist/6455/

All I know is that the more expensive bearings are usually better, but not necessarily.


About the angle of the lower control arm. For the strut design (pic above) I have 8 to 10 degrees down angle (although it's hard to see in the pic I used), and for the "stage two" with the SLA I found 4 degrees better to use.


Will (william.lucke@gmail.com) MSG #366, 04-22-2013 11:22 AM
      I started this thread on pretty much this very topic:
http://www.corner-carvers.c...owthread.php?t=47287

Spherical bearing dimensions are pretty standardized, so in theory anyone's bearing could work in those weld cups.

As that thread mentions, there are rod-ends and spherical bearings with integral seals. I will be starting with those and adding external seals for a "double sealed" installation.


zkhennings MSG #367, 04-22-2013 02:23 PM
      Would that be a modified 88 suspension? Why get rid of the toe link? Doesn't it help with anti squat in addition to toe?

Austrian Import (maximilian_ledworowski@csumb.edu) MSG #368, 12-03-2013 11:41 PM
      ttt

FieroNate (fieronate@gmail.com) MSG #369, 12-05-2013 05:27 PM
      Has anyone worked out the geometry points on a stock Fiero to compare with the new changes. I've been wanting to do something like this for a while. Also anyonentice the newer cars have unusual suspension designs with 4 and 5 point link arrangements?

Knight MSG #370, 02-24-2014 09:21 PM
      Any progress ?

Blacktree (m.blacktree@gmail.com) MSG #371, 02-24-2014 10:10 PM
     
 
quote
Originally posted by zkhennings: Would that be a modified 88 suspension? Why get rid of the toe link? Doesn't it help with anti squat in addition to toe?

I'm curious about this as well. What's so wrong with the '88 Fiero rear suspension that you'd want to get rid of it?


ccfiero350 (chuckcamp@gmail.com) MSG #372, 02-25-2014 09:08 AM
      There is not a whole lot wrong with the 88 rear suspension for everyday enthusiastic driving. In competitive circles, that boat sailed a long time ago but for a few odd balls that are unique in their choice of vehicle.

When you are building your dream car you are only limited by money, skills, talent and what you can get away with from the officials or wife.

The root problem IMO is the one year/one car only rear knuckle with its weany hub bearing. It really sucks when your wheel falls off in a race.



KurtAKX MSG #373, 02-25-2014 11:04 AM
     
 
quote
Originally posted by Blacktree:

I'm curious about this as well. What's so wrong with the '88 Fiero rear suspension that you'd want to get rid of it?


Not enough camber gain


Will (william.lucke@gmail.com) MSG #374, 02-25-2014 11:16 AM
     
 
quote
Originally posted by Blacktree:

I'm curious about this as well. What's so wrong with the '88 Fiero rear suspension that you'd want to get rid of it?


 
quote
Originally posted by KurtAKX:

Not enough camber gain


It does pretty darn well either raising the inner pivots or lowering the outers.

 
quote
Originally posted by ccfiero350:
The root problem IMO is the one year/one car only rear knuckle with its weany hub bearing. It really sucks when your wheel falls off in a race.


Totally agree. This is, IMNSHO, the achilles heel of the '88 suspension... very difficult to upgrade wheel bearings.


zkhennings MSG #375, 02-25-2014 11:57 AM
      How much of an improvement would a double wishbone setup, or multilink with two trailing links be over an 88 style MacPherson strut suspension with revised geometry (lowering outer pivots/raising inner)? Due to the high COM of the rear of the Fiero the static roll center can be pretty accurately placed by lowering outer pivots or raising inner pivots of 88 suspension. How stiff of a ride would you need to keep the roll center relatively close to where you want it versus a double trailing link multi link or double wishbone suspension?

I have been trying to decide on which way to go with a rear suspension design (which would be totally custom so knuckles would not be an issue) and use a strut based design or go to a double wishbone/multilink setup


Will (william.lucke@gmail.com) MSG #376, 02-25-2014 12:08 PM
      Either one can be made to perform quite well. Ferrari has always used double wishbones, but Porsche still uses strut front ends.

Get the tire to match the weight distribution, get the roll axis inclination to match the centroid axis inclination (or just make the roll axis a few inches lower in front) and you'll be most of the way there. Any rear suspension that gets the roll center high enough in the rear is going to have enough camber gain to make good use of the tires.

I have 215 front with 245 rear tires, stock front springs, softer than stock front bar, 325# rear springs and no rear bar on my '87 GT. It's pretty darn neutral. A modded '88 is going to be similar.

My Formula with rod-end lateral links and Konis is also fairly neutral, but has a slight tendency to slide the rear and a slight tendency to fishtail. That's on stock tire sizes.


zkhennings MSG #377, 02-25-2014 04:27 PM
      My current intentions for my Fiero are to be a weekend driver and a car I can drive hard at the track (semi full welded in cage, full racing seats and 4 point harnesses designed for street use). I currently have 350lb springs in the rear, and I do not know if I would want to go stiffer (currently 2.8, would go stiffer if swapped in a heavier engine) for the road as it is currently pretty harsh (Massachusetts roads). So I guess my hesitation with a strut suspension would be based on how the roll center moves side to side with roll angle. I have seen Blooze's graphs of the roll center movement in the strut based suspension vs his double wishbone suspension and it is significant. I am just unsure if the stiffness of the suspension bearable on the road would allow the car to roll enough that it would make a noticeable handling decrease.

The thing is though I do not know how much this would actually affect the handling in real life so I guess I am asking a theoretical matter of opinion of whether the additional roll center control achievable with double wishbone suspension is worth it.

I would overall like to stay with a strut based suspension in the rear, and knowing that a car can handle with struts (911) is pushing me towards that route, but I simply don't have enough actual experience with knowing how the roll center difference would feel.

And as far as centroid axis inclination is concerned, are the most important points to find the axis between the two centroids located on the wheel center planes? Because that is what I would assume, if there is an accurate way to find them.


Will (william.lucke@gmail.com) MSG #378, 02-26-2014 11:41 AM
      Roll center sensitivity is something that's way down the line in terms of importance... Although it is something that should be optimized if you're going to the trouble of building your own suspension.

You're probably 90% of the way there if you have static and dynamic contact pressures equalized front and rear.

Suspension design is less about getting everything perfectly right than it is about not getting anything grossly wrong.

[This message has been edited by Will (edited 02-26-2014).]

Bloozberry MSG #379, 02-28-2014 12:55 PM
      A couple weeks ago, Austrian Import (the OP) asked if I would update this thread with the findings from my own project where I'm building an F355 replica with a modified '88 suspension. First a little background for those who haven't checked out my build thread: I started by studying the effects of lowering and widening the stock '88 Fiero suspension and wasn't satisfied with the results. I was inspired by PFF member Datsun1973's design of a 5 link, pushrod system shown at the top of page 9 in this thread and designed my own similar system. PFF'er Zac88GT played a key role running many iterations of my suspension coordinates through his simulation software where I finally honed in on a configuration that lowers and widens the car, and theoretically improves most of the stock '88's handling characteristics.

Here's a summary of the modifications to the rear suspension:

1. Extended the wheelbase 76mm (3.0") to fit the stretched F355 body;

2. Replaced the Chapman strut with two upper lateral links, and a longitudinal coil-over shock absorber on a push rod & bell crank system;

3. Raised the lower lateral link mounts 97 mm (3.8") above stock through a combination of raising the cradle 25 mm (1.0") higher into the chassis and raising the link mounts an additional 72 mm (2.8") on the cradle;

4. Moved the forward inboard lower lateral link mount further outboard by 94mm (3.7"), and the aft inboard lower lateral link mount outboard by 123mm (4.85").

5. Shortened forward lower lateral link by 13mm (0.5") and the aft lower lateral link by 42mm (1.65");

6. Flipped knuckle to address a clearance issue with the new upper lateral link mounts and the inside diameter of the new wheel;

7. Replaced the stock wheels and tires with 18" x 9" et 45 wheels and 265/35/18 tires;

8. The net effect of the above changes increased the track width by 128 mm (5.0") (tire centerline to tire centerline), and increased the overall width of the car by 170 mm (6.7") (tire outer edge to tire outer edge) over stock;

9. Modified the trailing links to accept the new track width, and changed the location of the trailing link mounts on the chassis; and

10. Converted the brakes to 12" vented Corvette rotors.

These are side by side schematics comparing my modified rear chassis to the stock rear chassis:

Side view:



Rear view:



Top view:



And here are a few graphs showing some of the more important characteristics of the new design (pink lines) compared to the stock '88 Fiero suspension (blue lines). It's important to note that the new configuration gives the appearance of an 86mm (3.4") drop when compared to the stock wheel to fender clearance, and yet the suspension still achieves significant improvement in performance in most areas and retains approximately 5.5" of travel.





Here's a little schematic showing the how to interpret the above graph at 6 degrees roll:











And finally, a short video demonstrating the new design as it travels through it's range of movement.

www.youtube.com/watch?v=4n2...bDM&feature=youtu.be

For the diehards, the discussion, graphs, analyses and drawings of each of the four designs I considered before finalizing on this approach can be found in my build thread starting here: www.fiero.nl/forum/Forum3/HTML/000116-13.html


KurtAKX MSG #380, 03-03-2014 10:48 AM
     
 
quote
Originally posted by Bloozberry:

And finally, a short video demonstrating the new design as it travels through it's range of movement.

www.youtube.com/watch?v=4n2...bDM&feature=youtu.be


I've read your posts, and I understand what you've done and why you've done it.

It's very nice work.

There's one thing I can't figure out after watching the video-
how did you operate the floor jack in the video so smoothly, without stopping between strokes?


Bloozberry MSG #381, 03-03-2014 01:36 PM
     
 
quote
Originally posted by KurtAKX:
...how did you operate the floor jack in the video so smoothly, without stopping between strokes?


A good magician never reveals his tricks.

OK, so I'm not a good magician: I videoed the suspension on the down stroke only (which is easy to get a fluid motion), then simply played back the same video in reverse.



KurtAKX MSG #382, 03-05-2014 03:16 PM
      Good trick. I should've considered that.

zkhennings MSG #383, 03-05-2014 04:56 PM
     
 
quote
Originally posted by Bloozberry:


A good magician never reveals his tricks.

OK, so I'm not a good magician: I videoed the suspension on the down stroke only (which is easy to get a fluid motion), then simply played back the same video in reverse.


Wow I was wondering the same thing, I thought you might have one of the pedals on your jack that will lift it like halfway in one push (when unloaded)


wftb (danjesso@bmts.com) MSG #384, 11-18-2015 10:45 AM
      Just a bump .If anyone is interested , I have built and installed an SLA rear suspension in my 86 GT .(look in construction zone) Not tested yet but I hope to bounce it around the backyard soon .

Will (william.lucke@gmail.com) MSG #385, 11-18-2015 08:01 PM
      Link?

wftb (danjesso@bmts.com) MSG #386, 11-18-2015 10:44 PM
      thread is called " ecotec swap" .I am not great with computers , have no idea how to post a link .The new suspension stuff is on the last couple of pages .

wftb (danjesso@bmts.com) MSG #387, 02-26-2016 08:42 AM
      I have tested the new suspension in the backyard and I am happy so far .But we are back in to winter again so no pavement runs till early April if the weather cooperates .I will see if I can post a link here .Most of the work on the rear suspension is in the last 3 pages http://www.fiero.nl/forum/Forum3/HTML/000029.html

[This message has been edited by wftb (edited 02-26-2016).]

84fiero123 (84fiero123@excite.com) MSG #388, 02-26-2016 09:30 AM
      Why is it that engineers have to constantly change things?
Granted this can be improved on, but why?
I don't see model T people trying to improve their handling. I can see trying but they are 30 years old, they were designed to work and still have a trunk, why should you have to lose the trunk? I like the trunk in my Fiero, I need the trunk in my Fiero, I want my dam trunk in my Fiero so I will not be even looking at this thread again.

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work. The next newest idea is not always a good idea or may even work. look how often the technology changes those peace's of technology are just plain disposable in a year or sometimes less.

These cars have lasted 30 years and drive fine even today, have a great crash rating. sorry not a fan.

Steve



wftb (danjesso@bmts.com) MSG #389, 02-26-2016 10:11 AM
      The model T is the most modified car in history , and there are lots of modified suspension examples . I am building my car to have fun at the track . If you like a stock fiero that is fine but threads like this are not going to be to your liking .And I still have the upper half of my trunk .And my golf clubs fit in quite nicely .

ericjon262 MSG #390, 02-26-2016 10:48 AM
     
 
quote
Originally posted by 84fiero123:

Why is it that engineers have to constantly change things?
Granted this can be improved on, but why?
I don't see model T people trying to improve their handling. I can see trying but they are 30 years old, they were designed to work and still have a trunk, why should you have to lose the trunk? I like the trunk in my Fiero, I need the trunk in my Fiero, I want my dam trunk in my Fiero so I will not be even looking at this thread again.

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work. The next newest idea is not always a good idea or may even work. look how often the technology changes those peace's of technology are just plain disposable in a year or sometimes less.

These cars have lasted 30 years and drive fine even today, have a great crash rating. sorry not a fan.

Steve




why do engine swaps? all they do is make the car faster, does it need to go faster?


Steel MSG #391, 02-26-2016 10:51 AM
     
 
quote
Originally posted by 84fiero123:

Why is it that engineers have to constantly change things?
Granted this can be improved on, but why?
I don't see model T people trying to improve their handling. I can see trying but they are 30 years old, they were designed to work and still have a trunk, why should you have to lose the trunk? I like the trunk in my Fiero, I need the trunk in my Fiero, I want my dam trunk in my Fiero so I will not be even looking at this thread again.

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work. The next newest idea is not always a good idea or may even work. look how often the technology changes those peace's of technology are just plain disposable in a year or sometimes less.

These cars have lasted 30 years and drive fine even today, have a great crash rating. sorry not a fan.

Steve




Because some people have higher expectations and standards than you do?



Thunderstruck GT MSG #392, 02-26-2016 10:56 AM
     
 
quote
Originally posted by 84fiero123:

Why is it that engineers have to constantly change things?
Granted this can be improved on, but why?
I don't see model T people trying to improve their handling. I can see trying but they are 30 years old, they were designed to work and still have a trunk, why should you have to lose the trunk? I like the trunk in my Fiero, I need the trunk in my Fiero, I want my dam trunk in my Fiero so I will not be even looking at this thread again.

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work. The next newest idea is not always a good idea or may even work. look how often the technology changes those peace's of technology are just plain disposable in a year or sometimes less.

These cars have lasted 30 years and drive fine even today, have a great crash rating. sorry not a fan.

Steve




Because they're engineers.

They're never right the 1st.... 2nd.... 3rd..... 10th time.

My god, did I just agree with you?!?!

[This message has been edited by Thunderstruck GT (edited 02-26-2016).]

2.5 MSG #393, 02-26-2016 12:04 PM
     
 
quote
Originally posted by 84fiero123:

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work.
Steve





hot rod.

NOUN

a motor vehicle that has been specially modified to give it extra power and speed.

VERB

modify (a vehicle or other device) to make it faster or more powerful.



[This message has been edited by 2.5 (edited 02-26-2016).]

RCR (rcrabine@comcast.net) MSG #394, 02-26-2016 05:23 PM
      -steps onto soap box -
 
quote
Originally posted by 84fiero123:

Why is it that engineers have to constantly change things?

Sorry not a fan of this disposable society we have become, everything must be improved constantly to keep some engineer at work. The next newest idea is not always a good idea or may even work. look how often the technology changes those peace's of technology are just plain disposable in a year or sometimes less.

Steve




As an engineer (automotive electrical), I have to take offense to your statement. While true that engineers are trying to improve upon the last generation of an item, it is typically NOT engineers driving that change. It is the marketing and sales teams that drive things into obsolescence and the purchasing public that "needs' to have the latest item to one up their neighbor.

-off soap box-

(that might be the Patron speaking)

Bob

[This message has been edited by RCR (edited 02-26-2016).]

RWDPLZ MSG #395, 02-26-2016 07:54 PM
      As another automotive Engineer (also electrical), at least with wiring harness, the changes typically are driven by the other groups, or management trying to save money by cutting costs.

70% other groups making changes (improved parts, new supplier, cost reduction, etc.)
25% management wanting to cut costs of the parts
5% me wanting to tweak the design to improve it (like moving splices so they're in an easily accessible part of the car, and mirrored between the two sides, like the doors).

Most Engineers have also never worked on a car, and they wonder why I want to make stuff easier to service. I spent an hour a month ago showing another Engineer what each part of a car was because he wanted to learn.


84fiero123 (84fiero123@excite.com) MSG #396, 02-28-2016 10:30 AM
     
 
quote
Originally posted by RWDPLZ:

As another automotive Engineer (also electrical), at least with wiring harness, the changes typically are driven by the other groups, or management trying to save money by cutting costs.

70% other groups making changes (improved parts, new supplier, cost reduction, etc.)
25% management wanting to cut costs of the parts
5% me wanting to tweak the design to improve it (like moving splices so they're in an easily accessible part of the car, and mirrored between the two sides, like the doors).

Most Engineers have also never worked on a car, and they wonder why I want to make stuff easier to service. I spent an hour a month ago showing another Engineer what each part of a car was because he wanted to learn.


Oh I know all of that, problem is there are to many chiefs and not enough Indians.
And I appreciate when someone wants to learn what they are doing that was never taught in school, like WTF moron thought it was a good idea to put the gas line filter under a car, lower than the gas tank so that anytime you change the filter you get soaked in gas? Who's fkn bright idea was that? Not only that they have used that stupid set up on everything from Fiero's to Suburban's and everything in between for decades.

I liked when an engineer came down to the floor and said,

"It worked on paper"
or
"The computer said it works"

Well the dam holes in the dam doors don't match up with the carrots on the doorpad, You make it work.

You change the dam gas filter, on the ground and get gasoline all over you.

You change the rear load floor heater core without disconnecting the AC lines in a suburban.

You are right for the most part these engineers I speak of are the ones who haven't got a clue about how a car works or how much extra work they make a car owner or mechanic do because their design is not ergonomically right. Because no one talks to anyone else.

Get off your high chair and take a walk down into the shop, climb that bridge, try to repair a part on a car that is covered by plastic covers that take longer to take off than the part you have to replace.

No one talks to anyone else, not even the other engineers who are working on a related part.

Want to really learn just how fkd up the automotive world is read, read

Bob Lutz Car Guys VS Bean counters.

One hand doesn't know what the other is doing, and it shows in how something's are designed. And in some cases it is guys sitting right next to each other in front of a computer designing, Or department heads to other department heads about how this will work with that.

Steve