Quote:
Originally Posted by MarkR171
Just got back from my first even with the Star Specs. My first 3 runs were sloppy and felt like the grip was worse than the run flats. I let out 4 psi all around and took a full second off my time and the tires felt a lot better. What PSI do you guys recommend to run? I'm assuming lower than run flats, as I started with the door jam recommended pressures.
Managed to take 1st in D-Stock on the last run but it was close! Video shortly.
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What were your actual tire pressures? 4 psi lower than the tire jam seems waaay too low to me. I start with 39 front 41/42 rear COLD and work from there. Direzzas have fairly stiff sidewalls, but it's still not enough to keep the tires from rolling over without higher pressures. (On a lighter car it might be.) Chalk your tires and you'll see - I ran with lower pressures (34/36ish) and they rolled over like crazy and my times showed it. A large bump up made an immediate and large difference. I like some extra pressure in the rear (vs the front) to try and get some corner entry rotation. Some prefer slightly lower pressures in the rear for corner exit traction, but I've been able to modulate well enough to work around this, and I find the corner entry rotation counters some of the innate understeer largely experienced in autocrosses. (If you're plowing massively into a turn with heavy understeer, corner exit traction isn't gonna be what you're worried about, and you've already blown your time.)
So to answer your question, no, I run way higher than the runflats, not lower.
Continue to use large changes for testing, like you did (small changes can be difficult to discern positive/negative results from normal variation), but next time try going 4psi HIGHER instead of lower and see what happens.