I am in need of some help regarding a horrendous push that my car has been having at low to moderate speeds.

It all started 2 months ago. The night before some practice laps at Texas World Speedway I decided I would adjust my camber to be more aggressive. Little did I know that I was adjusting the toe along with the camber.

I had ‘Toe In’ in the front and ‘Toe Out’ in the rear. My camber settings were about –1 in the front and –1.8 in the rear. I obviously didn’t know what I was doing.

I started to wonder what was up when I was on the carousel barley holding 51 miles per hour. With the tires I was running I should have been well over that speed. Another thing that triggered my concern was being 10 miles per hour slower at the end of the front straight. I am used to being at 126 miles per hour and I was now somewhere around 116. If I attempted to turn at 116 the car would start to loose control. My brother racing behind me thought I was trying to drift or something, but the fact is I usually take the same turn at 126 without any problems.

It was a month later at an autocross event at Texas Motor Speedway that I started thinking my alignment was way off. At autocross speeds my car would push and not allow for any trail braking. My times were way off the mark.

After doing some research I found some settings that I hoped would cure my push, but it seems my push has gotten worse. I can’t seem to understand why. More aggressive camber and front toe out should make for better handling.

Here is a picture of what happens to my car now vs. what happened to it before I fiddled with the alignment…



http://img155.imageshack.us/img155/9567/badturnog8.gif

My new alignment settings should be better. Many very fast s2k drivers use settings like these.

 

Front toe should be zero to slightly in. Rear toe should be slightly in. Otherwise your "aggressive handling" is going to be so darty that you have to slow down in order to keep on top of it.

That's my opinion, anyway.

 

Use the camber settings from the left picture and the toe settings from the right.

 

Well I didn’t have time to change my alignment at all, but a few things at the track led me to believe that I have too much neg camber.

First, the car would snap into oversteer at high speeds almost as if my tires were over inflated. This made me think that my contact patch might be too small. So after a hard run I felt the inside and outside of the tires and noticed the insides were hotter than the outsides. So I lowered the tire pressures from 41 front to 37 front, and 38 rear to 34 rear and I was faster and more predictable. And even though the car still feels funny, I am able to rotate it at low speeds if I try hard enough.

So my theory is that the compound I am running wont allow me to pull the lateral g's necessary to roll the tire to a solid contact patch. I got my camber settings from people running r-compounds and I am running Hankook Ventus.

I have some video showing before and after, but I just got back and haven’t had time to post them. Basically the before video shows some moderate wheel sawing at high speeds never drifting far from a foot from any apex, and the video from a few days ago shows some sever wheel sawing at speeds 4-10 miles per hour slower than before with missed apexes up to 3 feet.

 

What Ventus tire? the RS-2? Are those pressures right after you come off the track? I've had that tire go up a full 10psi during a session at TWS, so take that into consideration.

Toe out in the front only improves turn-in feel - mid corner it will induce push as the outside front starts getting dragged around the corner once you are loaded up- that said I run a very similar alignment to your first pic(except more aggressive, 3/16 of front toe out and 1/16 of rear toe in, but your rear toe linkage is different than mine) and felt the car was pretty neutral to slight understeer at TWS recently, and trail braking would easily bring the tail around, but I was on 245/275 V710's as well so its hard make an exact comparison.

I also run alot less air in the 710's, 30psi and I bleed them back to 30 as soon as I park in the pit coming back from a session. 710s like low pressure though, YMMV on the Hankooks.

You might consider less rear camber...might induce more slip from the rears.

 

I am running RS-2s. My pressures mentioned are hot pressures.

I think I am going to set my car up with the settings from the right picture.

I think it is more important I give the front as much traction as I can before I take away traction from the rear.

Here is a video (35megs) of my fastest lap that day. My time is 2:06.2, which is slower than the time I got with the old settings running Kumho 712's.

http://www.sexyracing.com/TWS/nov06lap.wmv

The quality is kinda low, but you can tell that I am having to fight the car on what should be relatively easy turns. On turn 2 I am usually at full throttle through most the turn, here I take longer to get to full throttle and I am having to dance around the edge of traction a lot more than usual on that turn. The rest of the turns you can just see that I am having to deal with snap oversteer and basically just poor handling qualities.

 

So why don't you go back to the alignment you had before? A little more toe-in in the rear may help stabilize the rear.

Also, have you checked for any wear? Anything loose? Any bushings shot or loose? This would cause erratic handling. Your sig says you have a 2000, maybe the 7 year old car is in need of some new bushings are suspension parts.

Good luck.

 

Yeah I would try taking the toe-in out of the front and putting some toe back in in the rear. It looks like the car turns in ok, but as soon as the outside front loads the car goes to push really quickly - then the handling imbalance is exacerbated by oversteer on throttle.

I wouldnt take camber out of the front though, that will reduce front grip.

See if you can borrow a pyrometer as well, the RS-2 is an interesting tire - I found that its was easy to overinflate them and wear out the centers. I dont have experience on them in the S2k, but when I ran the S on Falken 615's I was only running 34psi hot all around the temps looked really good.

The RS-2 in my experience also often felt worse when they were faster. The compound and sidewalls are so soft that they exhibit a good bit of wobble at lower pressures, even though they perform best there. I found that you would have to turn in early, wait for the tire to set, then make your steering/throttle adjustments. It was definetely slow to react.

That said - they should be a good bit better than 712's, and if you were running sub 2:06 on 712's, you were doing quite well.

 

I dont have a pyrometer, but I could tell by just feeling it that my inside temps were higher. (after a run on my 712's with the old settings my outsides were so hot they were untouchable). On both the 712's (old alignment) and the RS-2's (new alignment) I could hold 50-51 miles per hour on turn 10 (the 2nd gear turn). I am just going to put my alignment back to normal. I have other wheels and tires and I get the same characterisitcs on any combo of tires. I figure I will just start from square 1 and work one setting at a time.

And also I have autocrossed my car with the RS-2's with the old alignment and had fantastic results being only 1 tenth a second slower than another s2k with r-compounds.

 

I had a similar situation at TWS this past weekend. The track was cold and slippery. I had high degree of front toe out on the right and off a degree of front caster. I was fighting the car all day, but managed to turn a 2:03 lap.

Just an observation given your alignment challenges and running RS2. Which I have a lot of experience with at TWS. You have great lines and do a great job of maintaining your momentum in the turns. Try not to white knuckle the steering wheel and smooth out your inputs. Instead of shifting down to 4th on the front straight. Maintain your speed in 5th through the transition of 1. Set your car up to straight line brake and shift into 4th. You should be able to flat foot the throttle through turn 2 into turn 3 where you will down shift into 3rd. I use to do the same thing as you until I had an advanced instructor show me the benefit of staying in 4th in his NSX. You will be able to carry more speed with out upsetting the car and limiting the number of shifts.

I like your toe setting on the right and camber setting on the left.

Hope to see you 12/9-10 at TWS.