[ZDan]

Note to OP et al, this is regarding track pressures, not autoX!

Icecreamtruk, what are your cold pressures? I'm getting hot pressures up to 36ish going out with cold pressures of 26ish.

I would have to start with cold pressures of about 20psi to get 30psi hot pressures. And I'm not going out with 20psi...

Originally Posted by Icecreamtruk

Like you say, for 99% of people this is good enough. 99% of people also dont bother learning or trying new things, so there's that.

99% of people are more likely to get themselves into trouble than to actually do any better by trying to "optimize" their pressures based on nebulous concepts like "tire rolling over", especially if they go into it with the idea that "lower pressure is always better/faster"...

I don't mind learning new things, but I have never had anything like the resources required to truly hone in on "optimal" pressures, which would pretty much take an open track mostly to myself and multiple sets of same make/model tires from the same batch on the same make/model wheels. Long/short it ain't happenin...

For 36psi hot, which feels fine to me on my streetish setup cars, I'm already going out with cold pressures as low as I feel comfortable with.

[*]The 200TW "cheater tires" like the RE71R, A052 and rival S always overheat, there wont be a point where you wont be able to get enough temperature on the tire, on the dry.

Better to err on the *high* side as lower pressures => more heat... So this is kind of an argument against running "as low as you can go".

[*]There is a clear point where you can clearly feel the tire rolling over, its not progressive at all, 1psi higher the car feels awesome thru the turns, 1 psi lower and the car feels like a boat after initial turn-in and is much harder to settle.

If you are near the ideal pressure, changes in pressure of +/-1 or even 2psi shouldn't *drastically* affect handling behavior. If dropping 1psi yields major fundamental changes in handling behavior, that would seem to indicate pressure is lower than the ideal range and falling into the abysmally-low range.

I.e. I don't think pressure vs. lap time should be a step function, where 1psi below "optimal" is a handling disaster. And if that *were* the case, it would again argue for ensuring your tire pressure is comfortably above the step...

[*]The lower the pressure, the faster I went, but sometimes I would need a second or third lap to get ideal temps on tires, all depending on pressure and ambient/track temps.[/LIST]

Wait a minute, are you talking about ideal hot pressure after only 1, or 2, or 3 laps at a time?

Also, a proper test for "optimal" pressures? Ideally with pressure the *only* variable, with enough runs at different pressures to remove effects from other variables including heat in the tire, number of laps on the tire, time of day, driver being "cold" vs. "hot", etc. etc. Ideally testing would also be *blind*, i.e. driver doesn't know what pressures he's driving on. Not easy to arrange...

Now do with this information what you want, flush it down the toilet for all I care, but I just want to point out that the "as low as you can get it" statement from me came from my own personal data gathering. I have been bitten on the ass many times already by trusting what "experts" or "experienced" people say.

Of course this argument says that no one should blindly trust what you say either! In an ideal world they could find out for themselves what their "ideal pressures" are. In the real world, I think they're going to be better off to err on the high side for hot pressures at the track. Which is more like 34-36psi fully developed (after multiple laps) hot pressures. 28-30psi "hot" would have people going out in stockish cars with narrow tires and no camber with only about 20psi in the tires. Not a great idea IMO...