__redruM

I think if I had guessed and said it was from experience, that would have been a lot worse than just participating in the discussion and giving my unedjucated guess. I also think more correct information was given this way. But if you every really want to find something out on the internet, google it:
http://www.tirerack.com/tires/tiretech/tec...e.jsp?techid=58

CobraTi

You bump the rear up that much and you'll REALLY feel the back end slide around. Trust me. My first two events in the S2000, the outside temp was under 50 degrees and I started my tires at 38 all around and everything was fine. The next event, it was over 80 degrees out and when I had the tires up that high, I had no grip whatsoever. Once I dropped down to around 35psi (hot. . .would be around 31 cold) it behaved much better.

I'd go the opposite direction, at least in the rear, to get more grip back there. If you didnt think the car understeered too much, keep the fronts where you had them. My tires aren't the greatest so I have to run the fronts a little lower than I want to get them to stick.

Slightly off-topic here, but if you were experiencing a lot of oversteer, be smoother with your inputs, both in steering and throttle/brake. Apart from when I had the pressures way too high, I've never felt the back end want to step out on me (unintentionally) unless I gave it too much gas in the middle of a turn.

wvphoto

i have autox'd my s2000 several times..
seems pretty ass happy compared to my z06

i would go 32 in the front and aout 25 in the rear.. get a bigger patch and better grip.. the ass will beat you around a cone every time.. LOL

its pretty fun however.. be safe..

just my opinion

RED MX5

[QUOTE=CobraTi,Jul 13 2007, 02:35 PM]You bump the rear up that much and you'll REALLY feel the back end slide around.

vacantskies88

Thanks everyone, I will let you know how it goes

jguerdat

Kinda late in the whole thread but back when the S was new and folks were starting to figure it out, it was determined that somewhere around 36f/32r on the S02s was the appropriate starting point. This was from national competitors who have better things to do than NOT know about pyrometers and handling characteristics.

There's no way I'd run less than ~2 psi from those pressures but might run more, if it proved out. Last year I ran 36/32 on the RE01Rs and found the setup to be very good.

Plus, I've been autocrossing since 1974 so I've been around a while to know the difference...

J's_Racer

hmm just to verify something guys i read on tire-rack tire tech. to decrease over-steer u run a lower front pressure and higher rear pressure (ie 35/40) , and to decrease understeer u run higher front pressure and lower rear (ie 40/35)

isn't it the other way around when u feel your car is over-steering a little , you drop the rear psi by 1-2psi? and keep the front as it is?

or if it is understeering a little , then i will lower the front by 1-2 psi?

cause i always been thinking its like that and i start out at 40psi all around on hankook tires on my s2000.

or does this highly depend on what tires im running , my alignment is stock with stock suspension.

RED MX5

Actually it can go either way. For example, if all four tires are at optimal pressure and you increase the pressure at the back, the contact patch at the rear will be reduced and the back end will slide out more readily. On the other hand, if the front tires are below optimal pressure and you increase their pressure, the car will turn in more quickly (because the side walls will flex less) and deliver more grip. However, if they were already at the optimal pressure (for grip) and you increase the pressure more, you may STILL get a quicker initial turn in due to the reduced side wall flex, but you will have less grip once you're fully turned in.

Increasing the pressure makes the whole tire stiffer, so more pressure gives a quicker turn in, but too much pressure will bow out the center of the tread and reduce the contact patch, reducing grip. Chalk will tell you whether you are rolling the tire too far over from under inflation, and will also tell you if the tire is grossly over inflated, becuase the chalk will wear off in the center of the tire first. It can also tell you if the camber is way off, but it's not very accurate. I've been autocrossing since 1969, so you can trust me as much as anyone else here, but I wouldn't let years of experience sway me. Not all experience is the same.
FWIW, my experience has taught me that the only way to get the tires and alignment just right is to use a pyrometer, and I'm convinced enough to say that anyone who says otherwise is mistaken (even if they've won every National Solo II championship since Moses was making bricks ).

You can get a pyrometer for about $100, or you can get a box of chalk for about a buck, but believe it or not, the pyrometer is well worth the difference in price. If you can't afford one, just borrow one at the event. Even here in backwoods Georgia there are always a few people carrying their pyrometer to the events.

J's_Racer

so a pyrometer will tell me best with the temp reading of the tires outside/inside/center ?

hmmm

vacantskies88

Left my house with tire pressures at 42 F/35R cold, got to the track and did my first run (45/38 now that they were warmed up).

First Run (45 F/38 R)
36.425 seconds

Second Run (45 F/35 R - took 3lbs out of rear for less oversteer)
35.290 seconds

Third Run (43 F/35 R - took 2 lbs out of front, felt 45 was a little high)
34.748 seconds

Fourth Run (43 F/35 R - kept same tire pressure all around)
34.320 seconds


Had a great first autocross with the S, just rolled 5,000 miles the other day (2001)