There's been a lot of debate about this subject in the past. While surfing around today, I found this information on the Kumho web site and thought it was concise and easy to understand. The comments are in reference to the Kumho V700 DOT racing tire, but, I think they apply well to any tire. One word of caution: For those of us who say "reduce" tire pressures to increase grip, we are not necessarily wrong. When the HOT tire pressure exceeds the tire's maximum (usually due to using a cold setting which is too high), reducing air pressure is actually the way to go. A tire that overheats will become "greasy" and cause understeer or oversteer in an unpredictable manner.

BTW, I tried 35F and 32R last time I was at the track and I still had buckets of understeer. So much so, I was laughing all the way through corner exits. For years, people imagined that RWD cars oversteered and FWD understeered, but, nowadays, it's all in the way you tune the car.

I would ask that all you track guys post their most susccessful tire temperature settings here. Just remember to specify the tires and suspension used. If we get enough posts, I'd like to see this post become a permanent note because it is the cheapest form of tuning on the planet. (VQRacer are you out there?)

"Tire Temperatures
The V700 will work well on most cars with inflation pressures between 35 and 40 psi ("cold" inflation pressures for autocross use and "hot" inflation pressures for racing use). Cars that are light, well balanced and relatively easy on tires will find slightly lower pressures may work for them, while heavy, high horsepower cars that are generally harder on tires may find that they need slightly higher inflation pressures.

Generally adding air pressure in small increments (2 psi) to the tires on the end of the car that looses traction first works best. For example, if a car is understeering, add pressure to the front tires. If the car is oversteering, add pressure to the rear tires."

Thanks Kumho for the words of wisdom.
Fly

 

My last track events in California saw me using stock rears (040s) and new SO3s up front on my Redline track. I agree with Raceboy's reccomendations to keep tire pressures (both F & R) under 40#. This meant starting at about 35# cold and checking tires every session. Bleeding tire down as the days got warmer helped and I tried slightly higher rear pressures (2#) to help the understeer.

It made only a slight difference on the stock suspension. At both Buttonwillow and Willow Springs, I felt this delivered good results and kept tire temps across the entire tire fairly even.

Next track event will be June 7th at Second Creek Raceway in Denver (see SW forums for details).