I'm interesed in a primer on tire pressure from some of you more experienced races. I'd like to know what procedures to follow as I go through several AutoX runs. I've been running 38/34 cold and adjusting to maintain those temps as the tires heat up. Is this the proper technique? I've noticed pressures vary as much as 4 psi cold->hot and was curious about proper adjusting techniques.

Thanks!

 

The general recommendation is to set 'em cold and leave them alone unless you're actually making a change for balance.

For one-person cars, this would be the way to go. For multiple-person cars, you may need to balance cold pressures against hot pressures so that everyone has about the same performance. Testing and experience will dictate what to do in this case.

 

Joe, I assume you're suggesting he start cold a few PSI below his target, that feels right to him? I've always done as he does, maintain a steady PSI (around 41/37 for me). And I'm never happy with the grip in my first run. It always feels like I'm running on ice until the SO2's warm up.

 

I try and maintain the optimum temp.......or should I say "my" optimum temp as I go through my runs. I start with 38/34 and after each run I adjust the pressures down to the target 38/34. I found that if I don't adjust as I go the car doesn't handle nearly as well on the 3rd, 4th, 5th run as it did on the 1st or 2nd. And as stated the car is never as good on the first run but I've atributed that more to cold rubber than pressure. I guess I'm on the right track!

Oh one more factor that may come into play. Our run groups tend to be fairly small, 30 cars, so the tires don't have as much time to cool between runs.

 

Obviously, it depends on many variables. With little time to cool down, warm pressures would probably be a better way to go. I have at least an hour between runs so it's basically cold for me - warming of the air by the sun does more than any run. Also, I've not had an opportunity for test-and-tune so I'm just running what others have reported to be good starting points (36f/32r).

A major variable may be your driving. I consistently go faster with each run (except when I screw up, of course). I've been doing this for 25 years or so and my driving style is set. (Well, the S2K is causing me a major re-learning curve.) That means I attack each run as if it's my last. The work done by the tires can be considerably different. That can cause you to feel like the grip is lacking when it's really that you're over-driving the traction circle. Unlike road-racing where you get to practice and get to check tire pressures hot, this is a one-shot deal that can easily be misread.

Does that mean I'm right and you're wrong? Not necessarily. Whatever you decide on should be a constant or you're throwing variables into the soup. You may want to spend time at something that allows you to test various strategies. Most folks I know of that are top runners set pressures and leave them alone but that isn't something cast in stone. Whatever works for you is what you should run but I'd recommend trying other strategies to make sure you've got the right one for you.

 

Mack, boy am I jealous. "...4th, 5th run..." We only get three runs here in La La land. Must be our 250+ entrants and our slow operations pace.

 

 

Penforhire try the tropical environs of south Texas..Blue Light Special no Waiting...In our Region we have an entire day of Practice ( in reverse direction from the main event on Sunday). This is followed by a minimum of 6 runs for the books on Sunday.
Track is an airfield with time posted in the 1:20 or so range ~ 1 mile.
Good Racing