It's a '95 auto. Stock everything. I'm running 245/45/16 BFG KDW's. They are a hard tire and don't get warm really at the track. I have really bad push unless I'm getting on the throttle hard. I've only ran one event so before I experiment - is this a case for lowering the psi up front or raising out back or... ? I had about 40psi in front and rear before.

 

You'll want to have the front Higher pressure than the rear. Try about 38 in front and 32 in back. You can put a mark on the side of your tire with a piece of chalk and see how much the tire is rolling after a run. Also try going into the corner a tad slower so you can come out harder which can be much faster in out cars. Hope this helps.

 

Front suspension in some way or another is either too stiff or just plain not getting enough grip. So maybe more negative camber, some 1/32"-1/16" toe out in front instead of zero toe, soften up the front suspension like the sway bar or shock settings...

Automatic cars handle a little differently when your on or off throttle, when compared to a manual as well, so some automatic trans people trail brake and have thier foot on the gas in corners to get the car to do what they want.

 

You're a newbie right? Welcome!
Slow down going into the corner. Maintain speed through the corner. Accelerate coming out of the corner. Once you start to steer, it's too late to slow down. You might be doing this already. It's a hard lesson to learn though. steering functionality can be thought of as what's left in the tire's grip after you subtract acceleration or braking from the tire's gripping ability. They only do one or the other very well. Doing both at the same time requires compromise.

Example. Let's say you can make it around a corner going 25 mph while coasting. But if you are dragging the brake slowing down from 25 to 20 the car might push out because the tires are trying to slow the car down too. Slowing down the front will push. Speeding up the back will come around.

Now the mechanical side.... Get an alignment that will give you some negative camber. A stiffer front sway bar might help. I also use shoe polish instead of chalk. If the polish is getting scrubbed off of the sidewall the pressure is too low. What pressure to run also depends on what kind of surface you run on and weather conditions. WE have a nice smooth asphault police skid pad that we run on. I usually ran 40/37 on my 245/45/16 Yokohama AVSi's.

 

Slow in fast out is the short way to say that, if the car is heavy then you will have to slow down even more, especially when its nose heavy.

 

Ok thanks guys. Yeah, I've only run one autocross so far. Hope to go again this weekend if I feel ok.

I'll try a bigger psi gap from front to rear. I noticed someone mentioned softening up the front and someone else mentioned stiffening it up via the swaybar. I have seen this ... seems like sortof a debate going on there. Would most everyone agree that a larger front swaybar would cut down on understeer? I wonder if just some poly bushings to replace the rubber ones would help a bit?

 

Increasing the front roll stiffness has a number of different effects, some of which help and some of which don't. Think of this situation as one that keeps suspension people from getting bored.

The primary effect of increasing front roll stiffness either by increasing the bar diameter, increasing the stiffness of the endlink bushings, etc., is to increase the lateral weight transfer that occurs up front. That is a more understeer / less oversteer effect.

One secondary effect is that the critical outside front tire is held closer to its optimum camber, hence you get better grip out of the same tire at the same pressure. I suspect that the slip angle curves are closer to linear as well. Note that this optimal angle is not necessarily 90* to the pavement; most radials apparently prefer some slight amount of negative camber during the cornering (just some FYI). This one is less understeer / more oversteer in nature.

Another secondary effect is that the natural frequency of the car in roll is higher, which translates into the car being quicker to take a set (which in turn places increased demands on the driver and his technique). Not sure what this means to the understeer/oversteer balance though.

A couple of notes about poly endlink bushings are in order:

First, they primarily affect the overall stiffness of the bar at very small roll angles. Eventually even OE rubber essentially comes up solid. Poly is more linear in its behavior (hint: linear is usually a good thing when talking about suspension response).

Second, do not tighten the poly bushings down to the point where you can see the poly bulging. That's too much, and it's entirely possible to fatigue-fail an endlink bolt as a result.

Playing around with pressures - best way to establish them is at a test and tune session. Typically, such a session consists of a skidpad and a slalom rather than a full course (it makes the timing results more useful). And a better term might be 'pressure difference'.

Norm

 

Two years ago (my first year at autox), my car suddenly started understeering alot. I thought it was my driving, but even adjusting my style, I couldn't get the understeer to go away. As it turned out, I had broken the rear, driver's side swaybar endlink off. Once I fixed it, the car was back to the normal amount of understeer... FWIW.

 

It took me a few autocrosses to figure this out (maybe I'm a slow learner). I'd go into a corner a bit hot, oh crud the car is not turning enough, I'd turn the wheel even more, and the car would plow straight ahead into the cones. I was turning the wheels too much, so they were skidding more than turning. I eventually learned how much I could turn without plowing, and to slow a bit if needed. The car also seems to corner better with some throttle.

My first few autocrosses I thought the car understeered alot, now it seems pretty well balanced to me, now that my technique has improved.

I'd vote for several autocrosses before changing the hardware, just tweak tire pressures for now. FWIW I run 55 psi front and 45 psi rear for 44 psi tires (BFG KD).

 

Thanks David. Seems like you're running the same tires as me. I had about 40 all the way around on my run. I'm still not sure whether I should add to the front or take away from the back, or both.

 

Maybe not the same tire, I have just "KD" I think the "KDW" is OK for rain.

Anyway, tire pressure can be a bit tricky, too little and the front can plow, and too much and the front can plow. My guess is you are too low in front, you could try 10 psi or so over the sidewall rating. If the sidewalls (or chalk lines on the sidewall) are scuffing you'll need more air.

 

Congrats on your first autox! You are on your way to having a lot of fun and learning a lot about your f-body. You have some good tips here, however, I would just focus on driving now and not worry about doing any mods until you get used to the stock set-up.

Right now it sounds like you are getting speed induced understeer (going too fast into corners). Slow in, fast out should be your mantra! Go early to the autox and do the course walk with the other f-bod drivers. They should be able to give you some good tips on how to do the course as well as car set-up.

I had a set of the KDWs and really did not like them. I'd pick a stickier street tire like some of the folks are using here.

Smile- it is good for at least a second off your lap times!