I'm a long time owner of several 88 Fieros. I've done a few engine/trans swaps but always on 88's. Starting with an 88 I know that no other GM rear spindle is close to what GM did in 88. With an 88 you are stuck with the suspension geometry unless you get very creative and spend a lot of $$$$. ( I know a few have done it).
I just picked up an 87 GT, with no engine, and have been hitting up my local Pick n Pull for ideas and any parts I may need for future projects. When looking at the rear spindle for the early cars, I notice that the spindle is very similar to what GM has been doing for years. Upper part has the two holes for the McPherson strut and the lower has the single ball joint. Many newer GM cars have this same setup and come stock with larger, vented, double piston brake calipers.
I know enough to know that they are not true "bolt on" spindles. And it may be that the top two holes are not capable of working with a Fiero specific strut, (holes to close, to far apart, drilled at wrong angle ect) and that we'd have to use hubs with the correct spline... BUT... has anyone tried to use newer GM spindles on the older Gen I Fiero rear suspension?
If the long pole in the tent is the holes for the McPherson struts it seems to me that we could create brackets like FieroGuru did for his when he relocated the struts inboard.
So, what are/were the challenges? Why cant we find a workaround that would allow us to use newer GM suspension parts on Gen I cars?
I have thought of this before but the obvious problem is that the Citation/Fiero strut bolts are at a different angle than all other struts....That limits both spindle and strut choices.....But now I am thinking that an Aluminum spindle using a different strut with more availability would be a great idea....Lighter mass, better brakes more strut choices.
Relocating the top of the strut would be possible with a coil-over conversion....On my Fiero, I converted it to 88 rear subframe/suspension, and of course had to convert to coil-overs and relocate the strut top. But there are only so many 88s out there, and most go to the crusher with the rear subframe and brakes.
I am working on solutions for the 88 front and back, but haven't looked at anything 84-87 (and probably won't). Generally speaking, for an upright to be compatible, all the following needs to be within an acceptable range.
Bolt pattern spacing (and size of the holes) at the strut Angle of bolt pattern from spindle to strut Tie rod placement (elevation) Tie rod placement (location - on top of steer arm or below) Tie rod distance from wheel bearing (length of steering arm) Steering arm angle from wheel bearing center-line
All of these come into play when you are trying to fit a new spindle under the car, keep the camber in the adjustable range, keep bump steer to a minimum, and not mess up ackerman angle (all these aluminum spindles are rear steer and we are making them front steer (if used in the Fiero front).
The other myth is that you will end up with something lighter... depending on caliper and rotor selection that likely won't be the case.
My motivation with the 88s is strictly to get larger wheel bearings (front and rear) for increased strength and stronger CVs to support my Turbo AWD LS4/F40 project.
Here is an overlay of the W-body spindle with the 88 rear spindle...
I am working on solutions for the 88 front and back, .... My motivation with the 88s is strictly to get larger wheel bearings (front and rear) for increased strength and stronger CVs to support my Turbo AWD LS4/F40 project.
Please Please, Please include a bolt pattern change to 5 x 4 3/4" front and rear and you can have my bank routing numbers for as much as you need.
Seems like I have heard of people transplanting Pontiac 6000 struts and knuckles as an assembly into the rear of a Fiero, in order to allow the use of the larger bearings/hubs/axles. I don't remember exactly what the story was, however.
Why dont you do it then let us know how so we can copy you?
Well after I posted the question, I went to Pick n Pull and grabbed a set of spindle units off the 2016 Buick Regal that I pulled the LTG motor from. I figure that even if they don't work for what I'm asking about, i'll still have a use for them down the road.
and the cool thing is that these have a 5x120 bolt pattern.
[This message has been edited by qwikgta (edited 05-22-2020).]
I am working on solutions for the 88 front and back, but haven't looked at anything 84-87 (and probably won't). Generally speaking, for an upright to be compatible, all the following needs to be within an acceptable range.
Bolt pattern spacing (and size of the holes) at the strut Angle of bolt pattern from spindle to strut Tie rod placement (elevation) Tie rod placement (location - on top of steer arm or below) Tie rod distance from wheel bearing (length of steering arm) Steering arm angle from wheel bearing center-line
All of these come into play when you are trying to fit a new spindle under the car, keep the camber in the adjustable range, keep bump steer to a minimum, and not mess up ackerman angle (all these aluminum spindles are rear steer and we are making them front steer (if used in the Fiero front).
The other myth is that you will end up with something lighter... depending on caliper and rotor selection that likely won't be the case.
My motivation with the 88s is strictly to get larger wheel bearings (front and rear) for increased strength and stronger CVs to support my Turbo AWD LS4/F40 project.
as far as light goes, I agree that it probably won't end up lighter, but you can offset a ton of the added weight added by the higher performance parts.
That being said, I'm very interested in seeing what you come up with.
------------------ "I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
(all these aluminum spindles are rear steer and we are making them front steer (if used in the Fiero front).
If you had a suitable substitute spindle, it's just a matter of swapping sides to make them front steer, right? That's what we did with some 1970s GM car. Maybe it was Nova to GTO.
Originally posted by sourmash: If you had a suitable substitute spindle, it's just a matter of swapping sides to make them front steer, right? That's what we did with some 1970s GM car. Maybe it was Nova to GTO.
Swapping right to left will get the connection points in the right general area, but until you verify what doing so does to bump steer and ackerman results might not be as expected.
That is the challenge with these conversions, anyone can take whatever upright they way, toss it under the car, modify the connection points to get acceptable camber and toe in the forward/stationary position and call it an upgrade. But if it has horrendous bump steer because the elevation and connection point of the steering arms to the tire rods are all wrong or it starts dragging/pushing one of the front wheels as you turn corners around town... the resulting performance is a downgrade from stock.
This is one of those areas where you need to go into it with eyes wide open and verify what you have stock and what you will have with the changes. There isn't a requirement to stay stock, especially if you plan to use the car in a non-stock manner, but you absolutely need to know if the changes you make will get you closer to your ideal performance or further away from it than stock.
Swapping right to left will get the connection points in the right general area, but until you verify what doing so does to bump steer and ackerman results might not be as expected.
That is the challenge with these conversions, anyone can take whatever upright they way, toss it under the car, modify the connection points to get acceptable camber and toe in the forward/stationary position and call it an upgrade. But if it has horrendous bump steer because the elevation and connection point of the steering arms to the tire rods are all wrong or it starts dragging/pushing one of the front wheels as you turn corners around town... the resulting performance is a downgrade from stock.
This is one of those areas where you need to go into it with eyes wide open and verify what you have stock and what you will have with the changes. There isn't a requirement to stay stock, especially if you plan to use the car in a non-stock manner, but you absolutely need to know if the changes you make will get you closer to your ideal performance or further away from it than stock.
Fully understand, but this is an itch i've wanted to scratch for the last 25 years. I can only figure that it can't be done and thats why it hasn't. there are too many 84-87 owners out there that could have done this, or maybe they have and it wont work. I have the time, and an 87 to play with.
Tangent: what could it possibly cost to have a spindle/knuckle newly cast (assuming the design was already complete) with or without drop geometry that would satisfy larger bearings? Has anyone got a recent handle on the cost to have cast?
Do the tierods mount on the top or bottom of the steering arms? Bottom would be better than top if the plan was to install in the rear of the 84-87. Generally speaking having the tirerod pivot as close to the same elevation as the lower balljoint will get you very, very close to zero bump steer.
The lower ball joint with the pinch bolt likely is larger diameter than the 84-87, so ball joint upgrade or some other work is likely needed.
The overall horizontal distance from the wheel rotor to the ball joint will need to be checked to see if installing this upright on the stock fiero a-arm will pull the wheels in, push them out, or leave them stock. Might need to rework the lower a-arm or might need to change axle lengths depending on what you are trying to accomplish.
The angle of the strut will likely limit wheel/tire clearance (probably 8" or less unless other modifications are done) and require moving the top strut mount outboard from stock. There is a limit to how far you can go as the spring (assume coilovers) will have to stay inside the upper frame rail as it is lower than the top of the strut tower. Just another thing that has to be verified either by a test fit or detailed drawings.
GM switched to a common wheel bearing mounting bolt pattern for most of the cars. So the W-body uprights I have been playing with have a 5x115mm pattern, but the C5 bearing with the 5x120 also bolts to it so having a wide range of available bolt patterns is pretty much a non-issue as long as you can find the right CV housing to work with your axles.
The cobalt SS upright is very similar to this one (I have several W-bodies, Solstice, C5 and others on the shelf, as well as an assortment of aluminum upper and lower a-arms).
[This message has been edited by fieroguru (edited 05-23-2020).]
Originally posted by qwikgta: Fully understand, but this is an itch i've wanted to scratch for the last 25 years. I can only figure that it can't be done and thats why it hasn't. there are too many 84-87 owners out there that could have done this, or maybe they have and it wont work. I have the time, and an 87 to play with.
But it has been done, but never made it mainstream... there are probably 20+ examples where people went down this path and ended up with running/driving cars. The issue is effort involved to bring it to completion, overall cost to get there, overall performance once complete, and is it economical to bring to market.
The issue is that using off the shelf parts will only get you in the ball park, but not able to get you precisely where you want to go. This is why most vendors who went down this path, eventually migrated to building the custom spindles to get what they wanted. Now 20+ years have passed and there are a lot of other OEM options to look at, but you literally are looking for a needle in a haystack... finding a suspension component that is 20 to 30 years newer with complimentary suspension design to a 1980s chassis. There likely is a "workable" solution, but "workable" means having an OK fit, OK performance, and moderate fabrication effort to make it work. To find this holy grail of a part is a costly endeavor. I easily have over $2000 in aluminum suspension and upright bits on the shelf and I still am still working the solution to better optimize the goal and at this stage it requires a new custom cradle which.
Here is an LS4 swap that started with a modified W-body cradle, kept the Aluminum upright, modified the toe link connection (I am not endorsing this method), and you can see the bolt hole mismatch between the upright and strut. This is nothing that some welding couldn't fix, but people willing to weld on a fully charged strut are probably in short supply. Purging the strut, doing the needed welding, and installing a strut cartridge as a solution is going to get spendy.
Here is a picture of a highly modified W-body upright being used in the front. The big thing to notice is the work to correct the location of the steering arm for his specific suspension design. Once you get into having to modify the part in 2-3 locations to make it work, you are not that far off from custom fabrication and able to better optimize the geometry.
Like I said, I am going down this path for the 88's because it is something I want for my personal car... but even at this stage, I can see that having something that could be brought to market at a reasonable price is well below 50/50 odds.
The biggest mistake that was made in the Fiero was the length of the rear tie-rod; A MacPherson strut type suspension should have the tie-rod length based on a Triangle using the top of the strut, and the inner and outer mounting points of the A-arm...The Fiero A-arm is approx' 12 inches long, and anyone looking at the geometry of the Fiero suspension will KNOW that the tie-rod, being ABOVE the arm, should be SHORTER than the A-arm....Yet they made the arm 15 inches long!
I believe that the engineer who designed the setup did not know anything about strut suspensions, and thought, "I will make the Tie-rod arm LONG so it doesn't change length over the suspension travel!".......But the A-arm WILL change length, so that longer arm will cause a bunch of bump-steer!
The Tie-rod length should have been around 11 inches...most of the rear suspension bump-steer would have been eliminated.
Whatever you do, make sure the tie-rod arm is shorter than the lower A-arm, and that it runs parallel to that lower arm.
[This message has been edited by cvxjet (edited 05-23-2020).]
Originally posted by qwikgta: With an 88 you are stuck with the suspension geometry unless you get very creative and spend a lot of $$$$.
Interesting. That's basically what I think about the pre-88 rear suspension. IMO, the '88 rear suspension is pretty damn good, right out of the box. With a couple hundred bux, you can roll your own suspension links (rod ends and threaded tubes), and have lots of adjustability. The one downside is lack of camber gain, but Fieroguru sells a kit for that.
Interesting. That's basically what I think about the pre-88 rear suspension. IMO, the '88 rear suspension is pretty damn good, right out of the box. With a couple hundred bux, you can roll your own suspension links (rod ends and threaded tubes), and have lots of adjustability. The one downside is lack of camber gain, but Fieroguru sells a kit for that.
I have two 88's and I've got a set of AMS lateral links on one of them, they have heim joints on the ends and have been working great for about 10 years. The second one has a set of WCF trailing arms w/ poly. Spindles are stock and both have 13" brakes on them. I don't have any issues with the 88 suspension.
My issues in this thread are for the 84-87 suspension. I haven't owned a pre-88 since 1995 and back then I just drove them, I didn't modify them. Walking around the junkyard all the time I see a TON of GM front ends with 12-13" brakes, aluminum spindles and wonder if they would work for the Gen I cars. Since I haven't owned one in 20+ years I now have a reason to see if any of those GM spindles/brakes will work. I have access to so many newer GM cars I just want to see if any will work.
As Guru has written, and i'm sure i will find out, while they may be close, I doubt i'll find anything that just "bolts on", I may not find anything even close, but I have wanted to research this for so long. I'm interested in seeing whats involved, not b/c I plan to make a kit or sell anything, just b/c I want to help the community with a chance for newer parts w/ multiple hub/bolt patterns.
The biggest mistake that was made in the Fiero was the length of the rear tie-rod; A MacPherson strut type suspension should have the tie-rod length based on a Triangle using the top of the strut, and the inner and outer mounting points of the A-arm...The Fiero A-arm is approx' 12 inches long, and anyone looking at the geometry of the Fiero suspension will KNOW that the tie-rod, being ABOVE the arm, should be SHORTER than the A-arm....Yet they made the arm 15 inches long!
I believe that the engineer who designed the setup did not know anything about strut suspensions, and thought, "I will make the Tie-rod arm LONG so it doesn't change length over the suspension travel!".......But the A-arm WILL change length, so that longer arm will cause a bunch of bump-steer!
The Tie-rod length should have been around 11 inches...most of the rear suspension bump-steer would have been eliminated.
Whatever you do, make sure the tie-rod arm is shorter than the lower A-arm, and that it runs parallel to that lower arm.
But in the Gen I cars, isn't the rear end just a transplanted X body front end? And if so, isn't the suspension tie-rod just the steering outer tie-rod that is hard mounted to the cradle, in about the same location and height as the original steering rack? If so, and if the steering rack was kept in place, would there still be a lot of bump-steer. in other words, is there a lot of bump steer associated with the X body cars. I was not aware that the steering rack had a significant impact on the suspension geometry.
I was hoping the Buick you have been getting parts out of would have the hyper strut but not the case. The steering rack and its placement has a lot to do with bumpsteer and if it isn't right it will upset things.
Over all, the older cars as they first came out with skinny 13" rims and narrow tires did not have enough bump steer to worry about. And the early tests do not even mention it. Going up to 15" wheels and wider tires made it more noticeable, as wider tires tend to follow road imperfections. As has been mentioned, the tie rod is too long but the worse thing is it is also in the wrong place on the cradle.
The thing I do not like about using an alternate spindle is they are always from the front of a front drive car so there is no parking brake. So for now I will just stick to a stock rear spindle with my home made SLA suspension and bumpsteer bracket. edit to add link to my bumpsteer bracket thread
But in the Gen I cars, isn't the rear end just a transplanted X body front end? And if so, isn't the suspension tie-rod just the steering outer tie-rod that is hard mounted to the cradle, in about the same location and height as the original steering rack? If so, and if the steering rack was kept in place, would there still be a lot of bump-steer. in other words, is there a lot of bump steer associated with the X body cars. I was not aware that the steering rack had a significant impact on the suspension geometry.
Rob
I can't tell from pics on the web, but I doubt that the Citation has this problem...I think it was just the guy who adapted the Citation front suspension to the Fiero was an incompetent "Drunk-chimp"....To picture what is going on during suspension movement, think of this; The A-arm tip moves in an arc with a 12 inch radius, while the tie-rod moves in an arc with a 15 inch radius.....you can see how much that would affect the rear wheel angles.....
wftb- would the Buick REAR brake calipers fit on those front spindles?
I have the total solution- we need to have all the states resurface all of the roads so they are smooth as glass....Then we'd have (Almost) no trouble with bump-steer!
I would guess not because most FWD cars have non vented discs on the rear usually with smaller calipers. Maybe Rob could have a look next time he is at the wreckers....
Seems like I have heard of people transplanting Pontiac 6000 struts and knuckles as an assembly into the rear of a Fiero, in order to allow the use of the larger bearings/hubs/axles. I don't remember exactly what the story was, however.
That's what I run on my Chumpcar Fiero. 1990 P6000 wagon hubs, spindles, and outer axle stubs. Big bearing, 5 x 115 wheel bolt pattern. No failures or issues. Other Fieros that get used for endurance racing seem to shed rear hubs regularly. Use the non-ABS hubs.
[This message has been edited by mender (edited 05-24-2020).]
Originally posted by qwikgta: My issues in this thread are for the 84-87 suspension.
I was looking at it from the perspective of swapping the '88 rear suspension into the pre-'88 Fiero. I figured it was a foregone conclusion that one would want to do that. But that may have been a bad assumption.
[This message has been edited by Blacktree (edited 05-25-2020).]
I took a look at my donor cobalt, which appears (still have to take the fiero axles off and do some measuring, but they physically fit in the hubs) to have CV axles that match the Fiero ones, but all the distances are way off.
Even if you did manage to find a knuckle that would work, what would you do for a parking brake?
But it has been done, but never made it mainstream... there are probably 20+ examples where people went down this path and ended up with running/driving cars. The issue is effort involved to bring it to completion, overall cost to get there, overall performance once complete, and is it economical to bring to market.
<snip>
Like I said, I am going down this path for the 88's because it is something I want for my personal car... but even at this stage, I can see that having something that could be brought to market at a reasonable price is well below 50/50 odds.
All I want is to be able to mount Corvette wheels without using adapters and experiencing catastrophic bearing failure. Like you said it's probably been done 20 different ways but I'm not smart enough to know which is the "best" way to achieve what I'm trying to do. I need one of you smart guys to build something that I can bolt on. Oh and I need it for an 88 and I need two sets. How hard is that?
All I want is to be able to mount Corvette wheels without using adapters and experiencing catastrophic bearing failure. Like you said it's probably been done 20 different ways but I'm not smart enough to know which is the "best" way to achieve what I'm trying to do. I need one of you smart guys to build something that I can bolt on. Oh and I need it for an 88 and I need two sets. How hard is that?
All I want is to be able to mount Corvette wheels without using adapters and experiencing catastrophic bearing failure. Like you said it's probably been done 20 different ways but I'm not smart enough to know which is the "best" way to achieve what I'm trying to do. I need one of you smart guys to build something that I can bolt on. Oh and I need it for an 88 and I need two sets. How hard is that?
LOL, I like your style. I have wanted to machine hubs in a CNC to be able to use larger bearings. BUT I do not have a CNC. SO,.. it could be as easy as sending me a HAAS TM3 wired for 5 axis and a tilting rotory table
LOL, I like your style. I have wanted to machine hubs in a CNC to be able to use larger bearings. BUT I do not have a CNC. SO,.. it could be as easy as sending me a HAAS TM3 wired for 5 axis and a tilting rotory table
Well I priced out what that would cost and looks like I'll be shopping for wheel adapters and just keep my life insurance paid up.
A few years ago, I remember seeing one of those Factory Five 818 supercar kits ... they used a 2003-2007 WRX or Impreza suspension (spindles and all) and remarking how similar it looked like the 88 suspension...
At 3:19 on this video you get a nice view of the rear spindle and what looks like an 88-like tri-link design.
At 1:36 you see the front setup. It would be funny to put a Fiero body kit on this 818 car...
This video here shows an Outback knuckle...but I can't imagine they'd be terribly different... When combined with the Subaru bearing (and struts) and outer CV...it looks like it may work...
That's what I run on my Chumpcar Fiero. 1990 P6000 wagon hubs, spindles, and outer axle stubs. Big bearing, 5 x 115 wheel bolt pattern. No failures or issues. Other Fieros that get used for endurance racing seem to shed rear hubs regularly. Use the non-ABS hubs.
Thank you! By the lack of comments, I thought that maybe I had hallucinated that. Not that I have anything at stake, one way or the other. (And I knew I didn't do that many drugs in HS.)
[This message has been edited by Raydar (edited 05-26-2020).]
Here's a picture of my bump steer eliminator on the right side of my '87 Chumpcar Fiero with the A-body spindles, hubs and Fiero struts. Rear link puts the outer pivot in the same plane as the lower ball joint and makes for quick toe adjustment. I used a longer bolt through the inner control arm bushing (Lemforder monoball now) to hold the inner heim on the toe link.
If this is used with the stock rubber bushings, the outer wheel will toe in under the cornering forces because of the solid rear link and the rubber control arm bushings. That also occurs with the stock toe link and that deflection might be what most people are feeling as bumpsteer. Any deflection or slop in the bushings will result in toe-out during braking, just before switching to toe-in when in the corner so it can make the rear move around a fair bit on corner entry. That seems to be largely taken care of with poly bushings, so I think that should be a first step as has been mentioned by several people.
Here's a trial fit of the left side on the bench. I added a tab that bolts to the part of the spindle that sticks down onto the square tubing for strength.
Rear brakes are 313 mm front rotors off a 2006? Jetta drilled for a 5 x 115 bolt pattern, with C4 Corvette HD front calipers. I don't need any more brake than that on the rear even for racing, no ducting so far and they're good.
[This message has been edited by mender (edited 05-27-2020).]
