Please critique my suspension setup

[gpricco]

Hey guys,

I did my first autocross today and I'm looking for some criticism on my suspension setup. The car is an E36 328 and it understeered pretty badly, to my surprise. I had understeer tendencies with this car back when I did a couple of HPDE's in 2013, but I was on different suspension then (Bilstein shocks/HR Race) and it feels even worse now. My driving skills need a whole lot of work so the car isn't really holding me back but I'm still pretty disappointed at how it behaves at it's limits.

TC Kline SA Coilovers
Camber-only plates
400# front
500# rear

TMS Swaybars
30mm front
24mm rear

Factory X-Brace
M3 front control arms
OEM rubber bushings throughout front suspension

Purple Powerflex rear subframe bushings
ECS poly diff bushings
Rubber RTABs with limiters
Rubber ball joints/bushings in rear

OEM 8.5" contours all around
10mm spacers in front
245/40/17 Hankook Ventus RS3

Alignment:
-3* camber front
0 toe front
-2.5* camber rear
0.20* total toe in rear

I think that's everything. What do you guys think, should this car significantly favor understeer? I know for a fact that the front of the car is 0.5" to 1.0" too low, as I get some fender rub during cornering. This is likely a big contributor to the problem and I will do my best to fix this for the future but my spring perches are super stubborn. Adjusting the rebound on the shocks helped a bit (went full stiff in the rear and a bit softer in the front by the end of the day) and I can adjust my rear bar to a stiffer setting for future events. Would ditching the x-brace help? Would you say my spring rates are too soft for performance driving? The car sticks well with these tires but turn-in feedback was disappointing, with what felt like sloppy body roll that would sloppily translate into understeer. If I timed a corner perfect with respect to braking and apex, the car would break free in the back a bit - so my driving definitely has a huge influence on this - but I'm still looking to do something about the setup. Any suggestions are really appreciated. Thanks!

[olemiss540]

I would say to start by raising the ride height, lowering the front of the car too much can result in very poor performance as the shocks can bottom out and the roll center can be messed up pretty badly if the lower control arms are past parallel. I wouldn't say the springs are an issue, as I ran those rates successfully in HPDE and the car was very neutral. If that doesn't fix it, a little more camber (maybe 3.5 degrees on the front) and maybe try going with a stock rear swaybar?

Does it happen on turn in or corner exit?

[gpricco]

Thanks for the reply. Agreed on the ride height, but wouldn't less rear bar only make my problem worse?

And it seems to be happening more during exit than entrance...

[Pat533i]

I always had understeer with a Turner front swaybar. I switched to a eibach and use it at soft for autocross. Much better.

[MINIz guy]

What are your ride heights (ground to jack point)?

What you have should be a very neutral setup. Maybe your ride heights are jacked up, or maybe it could be that you're just pushing too hard.

[NotoriousJJE]

If you are ure it's happening at corner exit, it shouldn't be the front ride height as weight should be transferring to the rear by then. If you aren't sure, front ride height could be the issue. IF the front shocks are bottoming out and ride on the bumpstops, your spring rate up front is going to be drastically higher.
I know most guys run at least 1" of rake front to rear. Anything above that is out of the norm.

Blown shocks?
Have you tried a stock front sway?
Same tires front and back in terms of make/model and age?

[aeronaut]

What they said. You've got all the right parts to make a good setup. So, set ride heights to something reasonable, double check components, tweak. The only thing different on my car are spring rates (I run 550/650, so same delta as yours, so that's NOT the issue), and different ARBs (UUC up front, stock in back).

[CoMZ302]

Just a side note - the X Brace cannot (in any way) cause the car to understeer. That piece "firms up" the front end of the subframe - while it is part of the suspension, it plays no part in the understeer/oversteer balance of the car.

Leave the X -Brace on there.

I'm not a fan of those great big sway bars (About the biggest you could put on there).

You may want to consider trying the front bar mounted to the control arm, just to try something different. By making this change, you'll reduce the effectiveness of the bar by about 30%. If the front bar is too stiff now, you should really like it after making the change.

Ground Control sells those parts - I can't find them on their new website, so just give them a call. You want the front sway bar mounts that attach to the control arms.

Also, you didn't mention where your front bar is adjusted? Does the 30mm bar in the front have different mounting holes for the end links? If so, you could also make sure you're in the softest setting (closest to the end of the sway bar on both sides).