Track pressures Dunlop Z1 Star Spec

[timothy]

Looking for guidance on hot tire pressures with Dunlop Direzza Sport Z1 Star Spec 225/45ZR17 front and 255/40ZR17 rear. The car has ROW sport suspension if that makes a difference.

[Topless]

36-40psi hot. Start at 38 hot all around and chalk your tire shoulders to look for rollover. If you get no rollover at 38 you may get a little better grip at 36psi. Different drivers also have different preferences in terms of hot pressure and sidewall firmness.

[sd_boxster]

EDIT:

Short version: I suck and have no idea.

Long version:

The perfect tire pressure is akin to the ideal woman - ask 100 guys, you'll get 100 answers. The guy who regularly snags TTOD at the AX events I go to runs at 34 PSI all around. The only guy who beats him runs 37/40.

I realized the folly of my tire pressure angst a few events ago. From now on, I'm not going to try to dial in the "perfect" tire pressure until I'm within a few seconds of the best driver in my class. When the day comes that I'm consistently running amazing times and need to fine-tune my tire pressures to shave off a quarter-second, I'll be a happy guy.

Unfortunately, I suspect this will be the same year I win the Nobel peace prize and Bank of America has to increase the size of ATM LCD panels because my bank balance keeps wrapping to two lines.

[sd_boxster]

PS - guys who refuse to share their tire pressures - like it's a state secret - really piss me off. Heh.

[timothy]

Thanks Topless. Just what I was looking for. Does matching the front and rear tire pressure give more neutral handling on the track? I expected something several pounds staggered as with the street spec.

[timothy]

Originally Posted by sd_boxster

PS - guys who refuse to share their tire pressures - like it's a state secret - really piss me off. Heh.

You think that's hard, try getting their BBQ meat rub recipe!

[Topless]

Originally Posted by sd_boxster

EDIT:


I realized the folly of my tire pressure angst a few events ago. From now on, I'm not going to try to dial in the "perfect" tire pressure until I'm within a few seconds of the best driver in my class. When the day comes that I'm consistently running amazing times and need to fine-tune my tire pressures to shave off a quarter-second, I'll be a happy guy.

SD Boxster is wise. Get your hot pressures in the 36-40psi zone and don't sweat it too much until you are knocking at a course record in your class. I do like even pressures all around but others have different ideas. Do chalk your sidewalls and look for shoulder rollover. A tire that is under-inflated for your driving style will overheat and wear out quickly.

[thstone]

I try to run 36psi hot all around.

Be sure that you have the car aligned with as much negative camber as you can get (assuming stock suspension). With a street alignment (~0 deg camber) you'll run too heavily on the shoulder of the tire regardless of how high you crank the tire pressure.

The more track time I get, the more I learn how complicated tires, tire pressures, alignment, and suspension are!

[timothy]

Thanks all. Next time I'll try the 36 - 38 range and see how that feels. Last weekend temps were in the high 90s and the tires got too hot. I lowered the pressures and had the rears at 38 but the front tires several pounds lower. It was a blind guess and the front tires felt low during warmup laps. I knew this week the forum members would set me straight.

@thstone the shop aligned my car with negative camber to prevent that very thing

[BudmanV24]

I'm running that exact same tire combo. I've been running stock pressures HOT. So 29/36 when I come off the track. They seem to get greasy towards the end of sessions so I figured adding more air would only make that worse. I also found it odd that I'm wearing the centers out on the front tires more so than the sides almost as if they're overinflated. This is more than likely due to the fact that I squeezed them onto a 6.5" rim which is 0.5" below the recommended minimum width.

[thstone]

I ran 33F/36R hot over the weekend on the roval (infield road course + 2/3 of the oval) at Auto Club Speedway in Fontana, CA. These were the perfect pressures for my driving style on that track (generally nicely balanced but with just a bit of understeer as I approach the limit).