The White Bug (Page 26/46)
Will FEB 19, 08:33 PM
Rotates the entire front suspension "forward" around the rear pivots of the lower control arms, which are fixed to the body.
Yes, it raises the body an inch on the suspension, but he has 2" lowering knuckles.

In stock form, the rear pivots of both upper and lower control arms are below the forward pivots. This is done for ride quality (I guess) so that the wheel moves back when it hits a bump. It also means that braking forces compress the suspension, resulting in pro-dive. Rotating the suspension forward makes those pivots level, eliminating pro-dive. The Fiero finally brakes flat like a supercar.

I pioneered the concept. It works amazingly well.
ericjon262 FEB 19, 09:04 PM

quote
Originally posted by La fiera:

How do those spacers work?? If you add height there is more potential and kinetic energy to be added during braking thus creating more dive! How does your anti-dive plates work?



I also added drop spindles, the net change actually lowers the car, and the spacers are a negligible amount of mass, so kinetic energy change is also negligible.

They work by changing the angle of the control arms. I haven't driven the car with them yet, so I cannot confirm how well they work. I think further discussion should occur in another thread though.

------------------
"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."

cognita semper

pmbrunelle FEB 20, 11:06 AM

quote
Originally posted by Will:
In stock form, the rear pivots of both upper and lower control arms are below the forward pivots. This is done for ride quality (I guess) so that the wheel moves back when it hits a bump. It also means that braking forces compress the suspension, resulting in pro-dive. Rotating the suspension forward makes those pivots level, eliminating pro-dive. The Fiero finally brakes flat like a supercar.



So you don't actually need anti-dive for a "good result"?

How much elevation difference is there in a stock Fiero between the front and back LCA pivots?

I was thinking that with your spherical bearing kit, I might be able to simply move the pivots a bit without having to move the crossmember.

Also the UCA tube could be welded on with a different angle onto the crossmember.
pmbrunelle FEB 20, 11:22 AM

quote
Originally posted by La fiera:

I changed the way the car transfer its weight back to front and side to side. The theory behind it is to have more rear bite by preventing some weight from transfering back to front while braking. I went from 350lbs springs all around to 700lbs fronts and 900lbs rear. I'm trying to eliminate nose dive, and body roll which delays response time, I also like my cars/karts a bit on the loose side so I can "dance" through the corners. Do you still think the brake bias would be the same? Thanks in advance for your input Patrick!




The ideal brake bias depends on the weight on the front/rear tires, and how much you want the rear loose on braking.

With the stiffer springs / anti-dive, you don't (during sustained braking) change the amount of weight transferred from rear to front, even though the body of the car pitches less. Therefore, your bias requirement shouldn't change.

However, with stiffer springs / anti-dive, you do get the weight transferred more quickly from rear to front. Therefore, you don't have to be as careful with slowly/smoothly applying the brake pedal to avoid locking up the front tires before the weight has been transferred.

[This message has been edited by pmbrunelle (edited 02-20-2021).]

ericjon262 FEB 20, 02:30 PM

quote
Originally posted by pmbrunelle:


So you don't actually need anti-dive for a "good result"?

How much elevation difference is there in a stock Fiero between the front and back LCA pivots?

I was thinking that with your spherical bearing kit, I might be able to simply move the pivots a bit without having to move the crossmember.

Also the UCA tube could be welded on with a different angle onto the crossmember.



one of the things that will need to be considered, is that with the spacers, the spring moves with the crossmember, by moving just the mount points, your springs will provide less force.

I'll take pictures of the crossmembers later, but I'm also not convinced it would be easier to remove and replace the the pivots. there's alot going on around the UCA tube, and lowering the LCA forward pivot an inch would also result in clearance problems with the edges of the stamping.

------------------
"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."

cognita semper

Will FEB 20, 03:50 PM
Also, changing the *relative* locations of the pivots will alter the bump steer curve from... whatever it looks like now to... something else. That's why I went to lengths to figure out how to make wedges instead of flat spacers.

ETA: Also 2: doing this reduces caster to around zero. I have a design in my head for an adjustable UCA that could fix that, and now that I have my design for the '88 mostly done, I'm working around toward building the design for the '84-'87 cars.

[This message has been edited by Will (edited 02-20-2021).]

pmbrunelle FEB 20, 04:26 PM

quote
Originally posted by ericjon262:
one of the things that will need to be considered, is that with the spacers, the spring moves with the crossmember, by moving just the mount points, your springs will provide less force.



The spring rate won't change, but if I move the front LCA pivot down, it will lower the ride height some... which is something I wanted to do. If I lower the car by this method, I'll maintain the same travel as stock, and I won't have to trim the front bumpstops.


quote
Originally posted by ericjon262:
I'll take pictures of the crossmembers later, but I'm also not convinced it would be easier to remove and replace the the pivots. there's alot going on around the UCA tube, and lowering the LCA forward pivot an inch would also result in clearance problems with the edges of the stamping.



Yeah, the UCA area might be tricky to work with.

I might just leave it alone, playing only with the LCA pivots may give some beneficial effect, considering that the spindle is closer to the lower ball joint than the upper ball joint.

With the lip on the crossmember, I'm expecting to do a cut+weld+patch job to accommodate a lowered front LCA pivot.


quote
Originally posted by Will:
Also, changing the *relative* locations of the pivots will alter the bump steer curve from... whatever it looks like now to... something else.



Right... some study will be in order.


quote
Originally posted by Will:
ETA: Also 2: doing this reduces caster to around zero.



By just moving around the LCA pivots, I should still have caster, since the UCA isn't moving forward.

Anyway, I need to think about this, suspension modifications won't be anytime soon. For now I'm in feasibility study / benchracing / dreaming / planning mode.
La fiera FEB 21, 08:36 PM

quote
Originally posted by pmbrunelle:


The ideal brake bias depends on the weight on the front/rear tires, and how much you want the rear loose on braking.

With the stiffer springs / anti-dive, you don't (during sustained braking) change the amount of weight transferred from rear to front, even though the body of the car pitches less. Therefore, your bias requirement shouldn't change.

However, with stiffer springs / anti-dive, you do get the weight transferred more quickly from rear to front. Therefore, you don't have to be as careful with slowly/smoothly applying the brake pedal to avoid locking up the front tires before the weight has been transferred.




Thanks Patrick! That was exactly why I switched to stiffer springs and you just confirmed that! Before with the softer (350lbs) springs all around I had to slowly apply the brakes to prevent reat lock up due to the bias and slow weight transfer. If I didn't get it precise, I had the car dancing from high speed braking (120mph to 40) to low speed while braking on a straight line and trail braking while turning.

[This message has been edited by La fiera (edited 02-21-2021).]

La fiera FEB 21, 09:35 PM
The other thing that worries me with those aluminmu hubs is the growth expation rate. For the street and dragway they will be just fine but at a 30min track session of repetitive braking from 80mph to 40mph happening 20 times per lap would mean an exponential growth of hub size leading to small clearances tightening the bearing and finally locking it!
That's why I personally decided to stay with the steel unit; its more forgiving. What do you think Patrick?
pmbrunelle FEB 21, 10:18 PM

quote
Originally posted by La fiera:

The other thing that worries me with those aluminmu hubs is the growth expation rate. For the street and dragway they will be just fine but at a 30min track session of repetitive braking from 80mph to 40mph happening 20 times per lap would mean an exponential growth of hub size leading to small clearances tightening the bearing and finally locking it!
That's why I personally decided to stay with the steel unit; its more forgiving. What do you think Patrick?



Before I ordered these hubs from Brian, I had this discussion with him.

My question:
Since the hub is aluminium, but the spindle is steel, have you heard of problems from the hub expanding with heat, making the bearings run too tight?

Brian's answer:
I haven't nore have any of my customers experienced any problems with dis-similar materials. 3 of my customers use my hubs on all out race cars including one that does 12-24 hour endurance races. No problems to report in the past 5 years.

I was satisfied with his answer (especially the part about the 12-24 hour endurance races), so I decided to try his hubs.