tire moving on rim at the track

[maytag]

Originally Posted by ianacole

I have a theory on this, for all it's worth.

Disclaimer: All my racing experience is in my old '02 VW GTI 1.8T. I've only done HPDE and open lapping in the Boxster as I collect parts for my Spec build.

Theory: All rotation happens under breaking, but the fronts are rotating further around the rim than the rears. I further theorize that the driver's side is rotating counter-clockwise, with the passenger side going clockwise.

Reasoning: I don't feel like these cars generate as much rotational force under acceleration as breaking. The only time I could see a great deal of acceleration force occurring is in standing starts, which I don't think occurs very often. Think about when you hear tires: under breaking, or in corners, never under acceleration out of a corner. I haven't had any telemetry hooked up in the Boxster, but in the VW, with ~215HP at the wheels, I could not break 1G under acceleration, but could regularly in breaking and cornering.

Anyone have any in-car telemetry they could share showing peak forces during acceleration and breaking?

Okaay..... I'ma be THAT GUY: It's BRAKING. Not Breaking. Though, honestly, I've had plenty of BOTH at the track, haha.

And no, as the images show clearly, the tires are rotating in opposite directions on the wheels, so they are not both happening under braking forces.
Also: I hear tire noise coming out of nearly ALL slower corners. You're suggesting that it's impossible to oversteer on these cars at corner exit, which is of course wrong. It's quite easy to do. So add-into the equation some sticky tires that don't break (not brake) traction as easily, and you've got a perfect environment for this sort of rotational movement under power.