Author Topic: Snap oversteer (Read 8025 times)

gearheadE30 · « **on:** October 29, 2007, 02:11:42 PM »

Is there a way to lessen the snap oversteer that our cars have, especially under braking? I've lost it a few times at autoX's when braking to enter a corner, and it seems that this could be a problem, especially on highway off ramps and someone pulls out in front of you. Which is what happened today, and the back end got REALLY loose :eek:. Any cheap ideas to fix this? The car has APEX springs, bilstien sports, an LSD, and that's about it suspension wise.

D. Clay · « **Reply #1 on:** October 29, 2007, 04:01:08 PM »

Braking too late?
"Snap" oversteer seems to imply that it is specific to rapid weight transfer to the front. There is a theory called "circle of traction" that basically says max cornering occurs during minimal front/rear weight transfer. That the more of one you have the less of the other. Ideally braking occurs in a straight line and then you turn into the corner. This is difficult in AutoX because of the tight turns, short chutes, and the impulse to go as fast as possible every instant.
The good news is that hopefully this also translates into a lot of bite coming off the corner. The cheap, easy, and immediate solution is to alter driving technique. Brake more in a straight line and then turn in. There will be more cornering force available going into the corner, more speed in the middle of the turn, and quicker into the gas coming off. The overall time will improve because the snap oversteer is screwing the rest of it up anyway. You will be slower in the little portion of the track where the snap occurs.
I have heard of complaints that Bilsteins have too much initial rebound which concurs with snap oversteer. Too stiff in rebound could suddenly take more weight off the rear.

gearheadE30 · « **Reply #2 on:** October 29, 2007, 05:46:27 PM »

Thanks for the reply. i do as much braking as I can in a straight line, but the car will oversteer with barely any braking. It may be because of the fact that it is a parking lot with gravel. I tried this on the last run of the day, and it cut off about 2 seconds

. The real problem for me was that it scared the crap out of me on the road. This was sudden braking in a corner though, so that might be it. There's a driving school coming up, so that should be a good time to practice.

silverblades181 · « **Reply #3 on:** October 29, 2007, 06:34:17 PM »

I've tracked my E30 318is with a similar suspension setup (H&R Sport and Bilstein Sports) multiple times on multiple circuits and I've never experienced snap oversteer. Maybe try to be more gentle with how you get off the gas and your initial bite during braking. My instructor pointed that out to me and it really helps keep the car settled. Or maybe there is something wrong with the car? Alignment?

nuvolarossa · « **Reply #4 on:** October 30, 2007, 07:15:17 AM »

lucky e30s! I can't get near never to loose the rear in my 318is e36...
I haven't LSD and with 225/40 18...
My car is neutral and I can feel more understeer overall...

gearheadE30 · « **Reply #5 on:** October 30, 2007, 01:43:48 PM »

Smoothness needs some work for me, but it wasn't the problem here. My pads suck so much that they have almost no initial bite to be jerky with. Is it possible that the rear subframe bushings could cause, or help cause, this? mine are original with 200k miles (mostly highway) on them.

Spec 2 · « **Reply #6 on:** October 30, 2007, 03:20:34 PM »

I've experienced this on the stock suspension with improper braking into the corner. Kicked myself near 150 degrees around on the onramp

It was early morning and I know I was hitting the corner a bit quick and hit the brakes immediately before turn-in, causing my balance to be thrown off and transfer weight to the front while the rear started kicking. That has been my case with 'snap' oversteer on these cars, though they naturally oversteer a bit.

John W · « **Reply #7 on:** October 30, 2007, 08:52:49 PM »

I'd defininetly check out the condition of your rear suspension bushings and your alignment. Also, are there any weird extremes between the front and rear of the car (tire pressure, spring rates, etc.)?

A couple of different impressions. ... I've never owned an e30, but had a 318ti with H&R race springs and Bilstein sports. That created a noticeable amount of toe-in at the rear of the car, but the car never experienced snap oversteer. It was actually quite nice because, despite not being a powerful car, you could put your foot in it to bring the back end out -- and control it with throttle to an extent -- or you could drive it like a front wheel drive car (trail brake) to lighten the rear (this actually worked quite well in the rain since it was too slick to get back into the throttle early).

My 2002 is different. (Bilstein HD/Eibach Sport/ 22/19 mm sway bars/ rebuilt subrames with urethane everywhere). Even after all that suspension work, it is still typical 2002 in that it has a moderate amount of understeer and gives only a hint before transition to oversteer. At that point, the back end will kick out a bit before regaining traction. When you're not used to it, it's weird at first.

FWIW, both of these cars have similar rear trailing arm suspension to your e30.

When I bought a Miata, inducing oversteer was much less forgiving. With its short wheel base, the transition to oversteer is more sudden. I've also autocrossed my friend's MR2 Spyder and it is a true mid engine car, complete with snap oversteer (these are great cars, btw).

gearheadE30 · « **Reply #8 on:** November 01, 2007, 12:24:13 PM »

i'm starting to think that what I thought was snap oversteer wasn't that at all. The car handles amazingly under acceleration and trail braking works great. I think I just got on the brakes way too hard and suddenly, eliminating rear traction. I also noticed that the driver's rear tire was low, so I fixed that and it feels much more reasurring

. Thanks for all the help, guys.

eric ^__^ · « **Reply #9 on:** November 07, 2007, 01:27:52 PM »

heh, I wonder how many people have died due to low tire pressure..

robweenerpi · « **Reply #10 on:** November 16, 2007, 06:14:59 PM »

My car does this on track some. Turn 10a-10b in Atlanta is pretty bad as it's bumpy near turn in and braking very hard. Fast hands can catch it if you know to expect it. Progressive rate springs don't help the situation much either...

E30's are always a bit 'happy' at the back end. My car is setup for mild understeer but if you are over agressive with steering input while trailing off the brakes the rear will come around. A little bit of toe in on the alignment helps out a bunch. I wouldn't refer to this as snap oversteer, just a light car with a short wheel base.

gearheadE30 · « **Reply #11 on:** November 16, 2007, 07:51:40 PM »

Yes, I know what the difference is. The combination of progressive-rate spings, stock sways, and low tire pressure were all causing oversteer that was not progressive at all. There was no warning and the car would literally swap ends, and even when I knew it was going to happen I couldn't stop it. Reinflating the tires fixed this, and oversteer is progressive once more

tjts1 · « **Reply #12 on:** November 17, 2007, 02:16:20 PM »

Swap in an open diff. I found my car much easier to drive at the limit with open diff. If you have good tires you don't need an LSD especially with just 130hp.

gearheadE30 · « **Reply #13 on:** November 18, 2007, 11:44:14 AM »

Well, after messing with the tire pressures in a parking lot, I've largely eradicated the problem. I also drove an open diff 325e (I know, it is a bit different with all that torque than an open diff would be on an m42) and it was really hard to steer with the throttle.

Author Topic: Snap oversteer (Read 8025 times)

eric ^__^