After reading the thread about the pending release of 225/45-15 Toyo RA-1's and Wai's mention of the Avon Tech R's, I got to thinking that it might be interesting and worthwhile to create a little 'knowledge base' thread here about how many heat cycles each of the r-compounds available can take before their performance starts to drop off noticeably. I'd personally love to know how many heat cycles you can get out of Hoosiers, Avon Tech R's, Kumho 710 and Ecsta V700's, Hankook Ventus Z211's, Yokohama A032R SC and A048R, Michelin Pilot Cup Sport, and any other r-compound I've missed.

As a Solo 1 guy with a co-driver (my dad) we put a lot of heat cycles on our tires every weekend at the track (16 per weekend, not including practice lapping) over the last 6-7 years (mostly in a 93 Civic hatch with various engines from built B-series to stock D-series). Here's what I've learned (keeping in mind that I compete in Ontario, where ambient an track temperatures tend to be quite a bit milder than say southwestern U.S.):

Kumho Victoracers (225/50-15) - excellent grip during the first two weekends of use (faster than Toyo or Yokohama in my experience). Do not work as well in cooler temperatures though, and grip level seems to really fall off after about 20-30 heat cycles. I've also found that these tires are very sensative to tire pressure. I've had to do a lot more work with the pressure gauge and tire pyrometer to get maximum grip out of them than with say Toyos or Yokohamas, but they do seem to be faster when fresh.

Toyo RA-1 (225/50-15) - very consistent tires. They do not seem to have quite as much grip as fresh Kumho Victoracers, though the difference has been quite small in my case (though I've seen others get better performance out of the Kumhos). The beauty of these tires is that they seem virtually unaffected by the number of heat cycles you throw at them. I've put 50-60+ heat cycles on these without noticing much if any drop off in performance. They seem to get faster as they get worn down to zero tread depth. They work very well on colder days too, and are fantastic in the rain at or near full tread depth.

Yokohama A032R hard compound (225-50-15) - also a very consistent tire, though a fair bit slower than the Toyos in my experience. Heat cycles do not seem to have much affect on these. They seem to have about the same grip level all the way to the cord. Fantastic lapping tire and rain tire, but for sheer speed the Toyos and Kumhos definitely seem to be faster.

Second-hand knowledge:

I have no experience with Hoosiers, but I've been told by a race team that runs through a lot of them that they get about 16 heat cycles out of the R04's before their speed really starts to drop off.

I have also been told by a long-time Solo 1 competitor that the Michelin Cup Sports are only good for a weekend or two of Solo 1 (so in his case that'd be about 10-20 heat cycles) before they start to take longer and longer to get up to temperature and stick well. He says they're a great tire for extended lapping/racing though, since they do seem to grip very well once they get up to temp. But for Solo 1/2 he does not like them because it takes too long to get the required heat built up.

That's all I've got, but it would be great to learn more about heat cycles and general tire performance from anyone willing to share.