mondo5x5 Posted February 22, 2004 Share Posted February 22, 2004 I have attended a few HPDE events and is currently running HPDE 2 but I have always wondered what the proper tire pressure I should be running. I also on occasion attend rallycross events and it is recommended to run tire presuures above the tire manufacturers maximum recomendation to prevent the tire from coming off the rim. I have been using the vehicle manufacturers recommended setting and without a pyrometer, I really do not know if I am running the correct tire pressures for a race track. Please help. Quote Link to comment Share on other sites More sharing options...
clock Posted February 22, 2004 Share Posted February 22, 2004 The answers to this question may differ greatly based on the type and size of the tire, driving style, and also the weight of the vehicle. Perhaps some more specifics will net you more answers... Quote Link to comment Share on other sites More sharing options...
CaptainWho Posted February 23, 2004 Share Posted February 23, 2004 These questions are so intimately tied to your driving style on a particular track in a particular car that all we could do is get you to a starting point for your testing. Which I'm sure someone around here will be happy to do when you give us a little more information. But you're going to have to fine tune it yourself. The lowest-tech and lowest-buck method to get started is to get shoe polish or tire crayons or something to mark the shoulder so you can see just how much you're rolling the shoulder under in the hardest corners. A pyrometer isn't necessary, but you do need to check and record cold and hot pressures religiously. If nothing else, you have to make sure the hot pressures don't get out of the tire manufacturer specified envelope. You need to make sure you can get (relatively) dry air if you live in a high-humidity area, like I do. This can be as simple as a water trap on an air reservoir. And you've got to keep in mind that the caster, camber, and toe have a big impact on it. If the camber or toe is way out of whack, no amount of tire pressure will get you there. Quote Link to comment Share on other sites More sharing options...
mondo5x5 Posted February 23, 2004 Author Share Posted February 23, 2004 I drive a Subaru WRX with 225/45-17 on all 4 corners. The car probably weighs approx. 3200 lbs. I would guess I can characterize my driving style as a little aggressive. Quote Link to comment Share on other sites More sharing options...
clock Posted February 23, 2004 Share Posted February 23, 2004 I drive a Subaru WRX with 225/45-17 on all 4 corners. The car probably weighs approx. 3200 lbs. I would guess I can characterize my driving style as a little aggressive. I drive a wrx as my commuter . I assume with those sizes that the brand and model tire is probably a performance street tire at least. In that case, CaptainWho's advice is perfect. Get your crayon and pressure gauge. Put a mark across the tire and up the sidewall, and see where your making contact. It really shouldn't stray from the tire cap. Start about 7-8psi under the factory max for when working with the street tires, and check the pressure again immediatly after you come off. If the pressure is over the max for the tire, start a few lbs lower than the ORIGINAL tire pressure you started with next session. That is important. You need to find a starting pressure that you start with everytime. If you check your tires once in the morning when it is 50 degrees out, by 2pm when the day has warmed, your tires can be dangerously overinflated. Bring an air tank to the track so you can make adjustments. Quote Link to comment Share on other sites More sharing options...
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