did I overheat tires?, rubber migration on A7 Options

[mskala]

This is what both my rears looked like after last weekend auto-x. It wasn't
even hot outside. Is this an indicator of anything particular I'm doing wrong?

About the only abnormal thing on the course was a long 180 that was not
quite a hairpin but I had the gas pedal to the floor for the whole last half of
it. Basically with a 2.3 and limited slip and my setup, no possible way to spin
with foot on the floor.

[mskala]

I appreciate all the suggestions.

I'm not doing anything but the local PCA autocrosses, and I don't need to go chucking
my tires after 30 runs after the 'best' grip is used. On the A6 I was using those for
about 10 or 11 events.

Some of the time we do 5 to 7 runs per session (half day) rather than 4. Back in
the day when I was using the Kumho, it took 3 runs before they were up to best
temp for grip, so I had only 1 shot at having a good run before having to wait 3 hours
again. On the A6 or A7 it seemed pretty good after 1 run of warming them up.
But unless my alignment is suddenly off or something, the A7 grip is worse after 4th
run.

Since I'm only in it for fun, and I mostly have to compete against myself, I'd be much
happier with a slower tire that doesn't fall off, than a faster tire that might be designed
for 3 runs before needing cooling.

At least with my streetable suspension settings, I never let the car wag too much
(and our courses are designed fast, usually over 60mph in a couple spots), it's not
easy to avoid spins. And I dislike the water sprayer thing. On tires that heat-
cycle out before the tread is gone, why do I want 8 mini-heat-cycles per day instead of 2?