Trailing throttle weirdness… (Page 1/1)
billy bee SEP 23, 05:14 PM
We have a 24 Hours of Lemons Fiero. We did our first test day at Buttonwillow. When lifting off the throttle and the braking point, the car is very darty. Stable in a straight line.

Feels a lot like the toe is way out. But it’s not. Feels
Like some crazy bump steer going from full throttle acceleration to brakes. Also, feels unstable under braking.

Stock springs, lightened car, 2 degrees negative camber in the rear. Zero camber in the front. Toe, front and rear, is zero.

Any Fiero handling gurus out there?

—bb
Patrick SEP 23, 09:43 PM

Mention the year of your Fiero.. as 88's are different than the rest.
billy bee SEP 23, 11:09 PM
Good point. It is an ‘88…
Patrick SEP 24, 12:21 AM

quote
Originally posted by billy bee:

It is an ‘88…



Check your two long trailing arm to knuckle bolts. I had a loose one after working on my Formula... and had a problem.

[This message has been edited by Patrick (edited 09-24-2022).]

Craig71188 SEP 24, 08:30 AM
Pre '88 are well known for trailing throttle oversteer, the '88 suspension redesign cured most of that. Static "0" toe in the rear may be an issue. If there is ANY play/deflection it can go to toe out and feel loose. IN general I like to shoot for minimal (equal) toe in for the rear. Front "0" toe is typically not a problem, in fact some toe out can help with turn in, however, if the front turns in too well, the rear can feel lose - it's about balance. Likely you have been through many of the steps below, but listed everything since I have no way of knowing. None of this is Fiero specific, just general race prep "good practices" for suspension set up.


1) Check all suspension components for play with the car on the ground/loaded (use a pry bar and have someone watch) - best/easiest to do on an alignment rack.
2) Check brake calipers for even pressures - raise car. apply light brake pressure, use torque wrench (beam type is easy to watch) and see if similar torque is needed to turn L&R wheel at each end
3) While on a level surface, check corner weights - excessive weight on one corner (or lack thereof) can contribute to issues when loading/unloading suspension.
4) Check shocks for leaks / blown seals / correct damping - a blown/malfunctioning shock can wreak havoc on handling during weight transfer
5) Check sway bars for preload. Align with one end of each bar unhooked, last step in suspension set up is to reattach the links insuring they do not need to be compressed or pressed out to secure.
6) When aligning, make notes of how much one turn of adjustment (or 1/4 or1/2 turn) changes toe. Set the front and rear toe to. -1" initially.

Once you have checked/adjusted as above, retest. If stable (and assuming you found no other issues), adjust front toe to "0" and see if it helps turn in while maintaining stability. If still stable, return rear to "0" toe and see if problem is returns or not.

cvxjet SEP 24, 02:31 PM
Check everything on both the rear and the front suspension for tightness, proper alignment, bushings, etc as has been mentioned.

I thought I had posted (Below) on a previous thread of yours but could not be sure (And could not find it);

I came up with an odd way of mounting my stabilizer bars so that I improved steering response/turn-in and yet also improved the drop-throttle-oversteer. The steering feels substantially quicker because of the car's quick response to steering input- yet the DTO is extremely mild. Usually if you improve Turn-in, you get more/worse DTO.

Here is a link to my thread on this (Crazy) idea; https://www.fiero.nl/forum/Forum2/HTML/140674.html

[This message has been edited by cvxjet (edited 09-24-2022).]

billy bee SEP 24, 08:42 PM
Good news! Following enerynody’s advice, I went over every nut and bolt on the suspension, front and rear. Found two problems on the left rear corner. The trailing arm bolt to the subframe was a little wonky. Proper torque fixed that. Similarly, one of the lateral links was not torqued correctly. Between the two loose arms, there was a lot of funk going on back there. All fixed.

Thanks for the help.

—bb