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(Ignore the fact that my pitiful performance at Laurinburg was in no way due to the car. I'll work on the nut behind the wheel separately.)
I'm running Hoosier A3S05, and this is the first season I've ever autocrossed on "real" tyres. I have a severe problem with not only finding the right pressure, but the procedure to do so.
I ran the TnT and seemed to have a handle on tire pressures. Balance seemed good, front and rear seemed to be working pretty well. In retrospect I didn't wait long enough between runs to get a baseline on starting cold -- as soon as I hit a real event, they were not working.
My current approach to pressures, which I now obviously have to throw out, was based on street tyres 15-20 years ago. I set the pressures cold at the beginning of the day, and added or subtracted a couple of psi if the chalk told me to. That's adding or subtracting from whatever the tire was at then, ignoring the actual value. That was good enough for mid-pack. (For Formula Vee racing I simply did whatever the guy in the Hoosier truck told me to do.)
I figured that would be close enough as a baseline until I got used to having a car that handled and tyres that stuck. Nope. Doesn't work.
I did notice I had a lot of trouble getting the tyres up to temperature yesterday, but stupidly dismissed it first as a cold weather issue, and second as a driver problem -- I was overdriving, and sliding too much would not work heat into the carcass. But later in the day I was still having the same problem despite it being warmer and backing off to reduce the sliding.
Then, when I was pulling the tyres off the car at the end of the day, checking them before putting away, I suddenly realised the rears had done no work and the fronts not enough. I know what a competition tire surface is supposed to look like if it's sticking properly, and the fronts showed about half the "working" texture I woud have expected, and the rears were simply smooth. Conclusion: they never reached operating temperature, and to me the most likely culprit at this point is the pressure being too high. But I don't know how to fix that without just blindly fumbling, as I've never had to do it before.
I have the feeling I could run the Hoosiers at 5 psi and the sidewalls still wouldn't flex enough to roll, so I'm guessing that chalking the tyres is pointless. Examining the surface gave me the first clue, but it's not subtle enough to use as a guide during the day (or is it?).
So, in simple for dummies terms, what do I do to get the pressures right? How do I set up cold for the first run, what tells me which way to go, and what data do I need to gather to use for future events?
One trouble is that even with the wrong pressures, these "slicks" stick so much better than anything I've autocrossed on before that I can't yet tell that they should be sticking even better. I do have a good feel for the limits of traction and how they behave there, and for the shape and feel of the curve, but in terms of the absolute of "they should stick this much" I have no idea. Later this year, if I keep working hard at it, my driving consistency should improve to use feel as a data point, but it sure as heck wasn't there yesterday. Until my driving stops sucking, what do I do in the meantime?
All advice, links, book pointers, slaps upside the head, whatever, greatly appreciated...
_________________ Martyn Wheeler AXing Kit's '05 Mazda 3, #29 HStock (when The Gonzo Symphonic allows)
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He says they're worth at least a second over the A3S05. That's at Sam's competition level, and presumably at yours too. At my level, the difference is unnoticeable, I'm sure -- I'm inclined to think that since I really like the feel of the Hoosiers I might stick with them, especially if what Hoosier says about their new A3S06 is true. But that's a moot point, I'm running the set I have until they wear out, or the end of the year whichever comes first.)
