Phokaioglaukos

I have read this often enough that I'm pretty well convinced it is true, and it would be easy (with proper tools) to measure temperatures across the face of the tires to check alignment, BUT I have seen no data at all on what temperatures are appropriate for street tires and little more for R tires like the RA-1s. There does seem to be more suggested tire temperature data being bandied about for Hoosiers, though. I e-mailed Pirelli about suggested tire temperatures for the Rossos, and had no response. That is one reason I have not invested in a contact pyrometer, yet.

Bob Rouleau

Chris - dunno about street tires but Corsa and Cup tires want 170-220 degrees F.

993inNC

Well like I said, to each his own. But I have ridden on many different tires, both street and R's and have never found a tire that liked being that high (which includes racing cars above and below that 3K lb mark). Tread depth will also play a part in the actions of the tire, but I'd be willing to bet you if you forget what the brains in suits have told you and drop those pressures a bit, you'll pick up significant lap times no matter where you run.
My last blue student did just that (went from over 40 to 34 on my firm request) and got noticeably faster. He knew it immediately and was astouded, couldn't believe all the times he had been out and learned to drive on "bricks". He told me that the car never felt so tight and that he didn't feel like the car wanted to "step out" on him. And this was a 2001 996 C2. The car had Pss9's (which he adjusted before our runs [thinking he tightened it up, but really loosened it up not knowing how to adjust the Bilsteins]), then he reduced the tire pressures......and got faster! Spectators even commented how much faster he looked on track. Just try it the next time you go to the track, if I'm wrong come back and tell me to keep my yap shut.......I suspect that you'd enjoy yourself

boqueron

993in NC, Bob

At the track I have told them many times that their suggested pressure for street tires, F40/R42 COLD was, following what I read at racing forums, too high. They kept telling me that with a lower pressure my tires would not last for long. I followed their advise as they have a record of more than 20 years training track drivers..

BUT...next track day I will follow your advise and go for +/- 40 hot....

Holger B

I run my PS2's 32-33 hot all the way around and that works well for me. Bob is correct that the sidewalls are very soft, but I haven't seen any adverse wear and at higher pressures I had oversteer issues.

There are so many variables that no single pressure setting is going to be best for everyone when you take into account driving style, driver experience, track conditions & configuration, alignment, sway bar settings, ride height, aerodynamics, tread depth, etc.

Bob Rouleau

Holger and 993 in NC - Interesting. At car clinics we've held for Porsches, pressures as you describe have resulted in excess shoulder wear and blistering on cars with a street alignment.

Street tire compounds like temps in the 150-160 F max range (lower than R's for obvious reasons) and with lower pressures I would expect temps to exceed the design limit on cars driven by experienced people. On GT3's running the Michelin Cup, the ideal pressure (with track alignment) is around 34-35 hot (a very narrow window in fact). Lower pressures help get the tire into the designed heat range,

I suspect the info provided by Michelin and Pirelli (40 hot) is designed to keep the tires in the correct heat range. Another factor is the track surface itself. I could see a highly abrasive surface wanting something different from a smooth polymer finish. The conclusion is that YMMV.

Best,

Seth Thomas

Not to flame you 993inNC but I don't agree with you on anything over 36 is too hot. This is not the case. At 36 you are just getting the tires up to their optimal operating temp and pressure range. The Toyo RA1s we run in World Challenge are perfect at 38psi, great at 40psi and good at 42psi anything over 42 and they fall off considerable amounts. 38 psi all around on a GT3 is a great pressure to aim for.

993inNC

Finally someone thank you.

993inNC

See now I've seen the opposite. But I believe excessive wear happens no matter what pressure is run when a driver doesn't use all of the track and forces the car (and the tires) to do things it doesn't want to do. The hardest thing I experience is trying to get people to use the track and stop over scrubing the tires, they just don't want to "track out" for some reason, and that extra stress on the tires I think over works them more than anything.


Maybe, or more for street use than competition. I mean really, what a bit of liablity to tel people how to set up the tires for the track

993inNC

We are all welcome to our opinions and I don't take yours as a flame, just another experience. But you're taking about a full prep'd race car, not a street car in DE guise. I'm guessing you run probably 2 1/2 -3 degrees negative camber if that Bimmer in your sig is what we're talking about. And lets talk about spring rate. Are you running soft spring rates (which would allow you to run higher tire pressures)?

All I'm saying is that I've run hard springs, soft springs, medium springs.....many different types of tires street alignment, race alignment and the one "constant" that I have found is that a softer tire pressure is a safer, faster and more evenly wearing tire. And when my students feel more confident after changing to lower pressures, and they get MUCH faster......we go with low pressures (and get no adverse effects).

Seth Thomas

I will dwell on this more tomorrow but in the meantime I want to ask if you are going to be at Roebling Road the second weekend in April, I believe April 8th? I should be coaching a guy at the school. If so I would love to converse more in depth about this. Very cool info. Thanks.

996FLT6

On Sportcups I run 31 hot all around so set cold pressures at 26/27. Works for me. I ran one time on cups at 36 hot and I was sliding abit more then normal(more like skating). On street tires I would run at 36 hot and go from there. Mike

993inNC

Unfortunately no. I'll be on my 10 year anniversary in Charleston with my bride that weekend, but had intended on being down there the end of April with a Florida PCA group.

I'm sure there is more than one way to skin a cat, but I have just found the tire pressure thing to be the cheapest and easiest way to dial in a cars handeling, whether suspension adjustments are capable or not. And the original post was about a DE car, where usually suspension tweeks are not an option, but a softer tire (to the correct pressure) allows for more "bite" when driven correctly.