993inNC

Have you ever taken the temps and pressures at the same time Larry? Usually anything more than 6 lbs comes from excessive heat due to incorrect camber, toe, etc....and the probability that the car was being driven to hard under wrong settings.
Not to say that your car doesn't handle (I wouldn't have any idea), I have just found that temps should keep within 20 degrees (inside to out) and 6 lbs pressure (give or take )

Bull

Chris, when I set up my cars, most recently my former 993 C2S and now my USA Cup, i include temp readings across the tires. I have never been able to keep the pressures from cold to hot within 6 lbs on my cars. These are fully adjustable cars set up for track with racing set-ups, not street/track compromises. In warm (80 degree) weather, the range is 8-10 lbs. This is very typical for my friends' track cars, and the cars set-up by the race shop.

993inNC

hmmm....I've always had the opposite, I can get 6 no matter the car (my old SCCA prep'd GTi, 993's), and although I drive smooth, I drive hard. To be honest, I often wonder if the more we "adjust", the more we actually do harm as it pertains to these subjects of pressures and temps.

Bull

If you are getting "even" temps across the tires with a probe, and "even" wear on the tires, and the car is handling well, you can't be far off of the "right" set-up for your driving. It was the same in my SCCA racing days. Once I get the set-up right for me and the track I'm on, I don't do any adjustments. These days the car remains the same for most tracks I run on.

SundayDriver

A little physics...

T1/T2 = P1/P2 where P and T are absolute. (Add 14.7 to pressure and 460 to Temp.) If you start at 30psi at 70 deg F and end up at 36 psi, then you are seeing internal tire temps of ~135 F, if I have my math right. Not exactly working the tires very hard.

Racing slicks will often see internal temps approaching 300F. Track tires should be near 200F if they are being worked hard and run near optimum tread temps.

38D

Agreed. I need to run low 20s (21-22) cold to get to 32 hot on dunlops slicks. On a really hot day you could be talking 18 cold (tires are still new to me). With MPSCs I would need to start at 24-26/22-24 cold to get to 32/36 hot.

Bull

One of the "friends" to whom I was referring.

Larry Herman

Chris, I just got back from an event at the Glen where we tested, and though I don't have the numbers readily at hand, the one thing that impressed me the most was that coming in off of 5 hot laps, the outside rear tire temp was around 185 degrees at all three points! And it was 37 lbs. My car wears the tires (R6s) incredibly evenly, and they last a long time, over 16 heat cycles. I also run minimal toe-in in the rear, with the monoballs you don't need much, just enough to prevent any toe-out. At some corners on that track, my car was actually faster than the 92 Eurocups which are 250 lbs lighter and run on slicks, so I know that it is working well. If you are only getting a 6 lb rise, there has to be another reason for what is happening there.

993inNC

That is pretty impressive Larry, I don't think I've ever gotten the same number all the way across. I tend to be 10-15 degrees higher inside to out. I'm impressed As for the 6 lbs, its been pretty consistent for me no matter the car and with pretty close tire temps, I've been pretty happy. Like Bob, once I get to a happy point, its "set it and forget it". I don't race anymore and don't get wacko over temps and pressures anymore, but I hadn't had to big a swing ever outside of my 6lb findings.

Larry Herman

I think that if your tires are working for you (and lasting), then you have a formula that works and that is pretty much what we all want. Every driver and car is different and though there seem to be some norms, it doesn't always hold true for everyone who is going quickly.

993inNC

Agree'd. My "norm" happens to be 6 lbs and seems to work. Thats my story and I'm stickin' to it

bobt993

Chris, driving style could very well make a difference. I had another drover borrow my car at SP Club Race last year when his car broke. Unfortunately because of the car sharing, tire pressures were set on his qualifying and sprint race to 36 psi. I went out for my race immediately following. After 3 laps I exceeded 42 psi (could be a warmer track) and my times slowed by 1.5 secs a lap (VERY greasy) and cars I passed starting coming back on me( I got lucky and ended up 3rd). It was my car, so I was pushing harder ( I was almost 2 secs a lap faster vs his best times). You may want to trade cars with another driver and see how tires, times, temp changes things.

993inNC

Well once you get past a certain point, its like throwing good money after bad. The tires get to hot, build up to much pressure and start handling poorly which causes you to drive harder in an effort to compensate, building up more heat and pressure and so on.......
I'm about at the point that I can tell exactly when I've reached that point (36+lbs). Anything over 36 and with my setup, the car handles like crap......

Larry Herman

Chris, R6s work well at your hot pressures, but it sounds like you are driving the car to maintain those temps. I can literally drive the ***** off of my car and still hold 35/37 with tire temps around 175~190. If you feel that you have to back off to avoid over-pressuring (not overheating) your tires, I suggest trying a lower cold setting and go out and beat the snot out of them. You may be pleasantly surprised.

230ERACER

Larry...right on, 36-37 is were most all of us are operating and getting great results this year. 4 days to the Clash. are you doing any tuning on Thursday w/ NY Metro?