hi guys,

ran a track day last week with our local toronto S2000's.

was just curious....what are the hot pressures that people are getting on the '04 bridgestones??

i have coilovers and a relatively aggressive alignment....hot pressures read 40-41 all day (all around).

car did about 500 track kilometres (300 miles).

inside and outside edges of front tires are pristine....had marble build up (down the middle) until last night....checked this morning and marbles are all gone now but the middle blocks are chunked/worn.

rear tires are pristine (but worn) all over. they wore evenly. no marbles were present at any time.

car had terminal understeer.

other than that, car was wonderful all day!!

 

Ok Nimesh, I'll take a swag at this.

The rears were evenly worn, so probably around the right pressure for best grip.

The fronts with marbles down the center, suggest that the middle of the tire wasn't making good contact to the track. The picked up marbles weren't being worn off like the rest of the tires. I'm guessing not enough front tire air pressure to maintain the tire patch causing it to pucker in hard corners. This would cause non-optimal grip, so a lot of understeer, since you could actually visibly see the uneven wear. Next time add a few front psi.

If you want to get more professional about it, give this a read:
http://www.popularhotrodding.com/tech/0311phr_tire/

 

There is another explanation for your tire wear, you may be running with too much tire pressure. A classic sign of an overinflated tire is excessive wear on the center of the tread surface with corresponding lack of wear on the edges, as you have described. This would also account for the buildup of marbles on the center of the tread. Remember that marbles buildup on tires not when running fast and on the racing line but when you slow down and go off the normal (clean) line. Once back up to speed and on the clean line marbles are abraded off of the tread.

A quick and dirty way to check your inflation is to take a piece of chalk or some white shoe polish and mark some small stripes from the tread area of your tires up an inch or two up the sidewall. Drive a session and at the end see how far up the sidewall the scuffing goes. If the tire is properly inflated you should wear the marking just to the edge of the tread and not onto the sidewall. If you don't get to the edge you may be running too much pressure. While this is no substitute for checking tire temps and doing proper suspension sorting it should get you into the ballpark.

 

thanks guys....

if i were to have "chalked" it (i didn't), the chalk would still have been higher up (approching contact patch) on the tread than not....

i think i might have had too much air in the fronts.

cold pressures last night were F33 R32....so, i'm a pound too high in the front (from stock).

either that or i need to remove a few click of stiffness from the front coilovers.

 

which coilovers are you running? Terminal understeer, huh? what alignment settings? I found my car to be pretty neutral with Tein Flex + Gendron front bar + 00-03 rear bar and -1.5 / -2.5 camber.

 

BC's set to 14 in the front.

my camber is similar to yours - give or take .1 of a degree.

should have also mentioned i have all 4 spoon bars.

and yeah the car started pushing, as i started pushing the car.

 

BC's are 10k springs all around, right? You might try an 00-03 rear sway bar... Mine is an 02 if I remember correctly. but be careful!