Question for all of you autocrossers out there. I have been playing with an 88 Formula for over 20 years now. Autocrossing and a few track days. The car is totaly striped out and many mods to engine and chassis. I am currentlt running 300# rear and 250# front springs on custom coil over shocks. Question is...... do I install 400# springs at the rear and move the 300# to the front? Any thoughts?
I think it depends on whether you want to change the understeer / oversteer situation. The 300 lb front / 400 lb rear setup is going to give you more oversteer. A 350 lb front / 400 lb rear setup would be closer to the ratio you have now.
That said, the Fiero usually uses stiffer springs in front, because the control arms have more leverage against the suspension spring. Are you using custom front control arms, or do you just prefer to have more oversteer?
Actually looking for a bit of oversteer. and to limit yaw. The front sway bar is stock but the rear bar is a bit stiffer and has adjustability. Was thinking about just the rear spring swap?
I do not have an 88 but with 250 lb springs up front I had way too much body roll .I went to 300 then to 350 lb springs in the front and now it is the way I want it .Right now I have 350's in the rear as well .I have run as stiff as 450 in the back . A little too harsh for me . With all the different springs I have used I have not noticed any changes in under/oversteer .That changes with the size of tires I use .An 88 is a different animal .
Stock spring rates for an 88 Fiero are 205 lb/in front, 147 lb/in rear. The motion ratios are about .5 front and .97 rear.
So the effective spring rate at the wheels are: Front = 205 x 0.52 = 51.25 Rear = 147 x 0.972 = 138.31 (255% higher than front).
Your existing combination: Front = 250 x 0.52 = 62.5 Rear = 300 x 0.972 = 282.3 (451% higher than front).
My 88 setup: Front = 600 x 0.52 = 150 Rear = 425 x 0.972 = 399 (267% higher than front).
My 88 setup is a stock weight (2800 lbs) daily driver/weekend autocross stock sway bars, konis on all 4 corners set full stiff, and 235/285 tires is pretty neutral and I can transition the car mid turn from oversteer to understeer with throttle application. So my suggestion would be to increase the front spring rate unless you have significantly changed the front/rear weight distribution (making the front even lighter).
[This message has been edited by fieroguru (edited 11-23-2016).]
The car is considerably lighter than stock. down to 2343# with 240# driver
LF 552# RF 458# LR 686 RR 647# cross 49%
Will increasing the front spring rate help achieve a bit more oversteer? Front shocks are 9 clicks (out of 12, QA1) toward stiff. Rear struts are 1/2 turn (Koni) off stiff. Tires are currently 225/45/17 on 7" rims on the front 245/40/17 rear on 8" rims. will be buying Hoosier A7 in the spring. Rear camber 3 deg neg, front 2.5 neg with 5 deg caster. Should probably reduce the camber a bit. Like the caster setting. Suggestions?
An easy way to get under/oversteer is to change the ride height .The old adage " the lowest corner takes the weight " works .The end with the lower setting will wash out first .If you want more oversteer , you can lower the rear or raise the front .Easy for you to do since you already have coilovers . Nice car !
The Obvious is not always the easiest. Trust me I've tried??????? Ride height is an option Glad I thought of it?? But should I be looking at different spring rates than what I am running now? The suspension is apart to correct a few items and now would be the time to make changes. I would like to thank all of you for the replies so far. Great advice, even the obvious...............
Have you calculated the natural frequency for the front and rear suspension? Generally speaking you want the rear to be 0.1 to 0.3 Hz higher than the front, and the range can be from .8 Hz for a daily driver to 2.2 to 2.5 for a dedicated autocrosser.
So you might want to measure what you have currently and verify the rear is slightly higher and where in the spectrum your spring rates put your combo.
There are lots of individual adjustments to bias oversteer/understeer but these are to fine tune. To effectively use them, you need the baseline setup in range.
If you need them, Blooze did a great job of detailing the 88 front and rear suspensions with the dimensions for the key suspension component locations at stock ride height. I have a copy... somewhere. They help give you a starting point, but then as you lower the car, change pivot locations and increase static camber, it helps to draw everything in a cad package to get the new coordinate data.
[This message has been edited by fieroguru (edited 11-23-2016).]
Bloozeberry's awesome drawings are still in his thread in the construction zone .He went away , sad ,but at least he left all his posts here .If you have not visited his thread , it is an eye opener .
[This message has been edited by wftb (edited 11-24-2016).]
It is the difference between a-arm suspension with the springs mounted halfway between the bushings and ball joints vs. a strut suspension with the springs pretty much on top of the tire. Even with the stock springs, the actual wheel rates are about 2.5 times less in front than rear, which more than takes care of the additional rear weight bias.
quote
Originally posted by fieroguru: Stock spring rates for an 88 Fiero are 205 lb/in front, 147 lb/in rear. The motion ratios are about .5 front and .97 rear.
So the effective spring rate at the wheels are: Front = 205 x 0.52 = 51.25 Rear = 147 x 0.972 = 138.31 (255% higher than front).
[This message has been edited by fieroguru (edited 08-04-2022).]
If your car is riding rough, first thing to do is use a camera/cell phone and see where the bump stops are to their stop for front and rear suspensions. Many people lower the car w/o addressing the bump stops and end up riding on the bump stops vs. springs which makes for a very stiff/bouncy ride.
[This message has been edited by fieroguru (edited 08-04-2022).]
