[240racer]

In general DOT tires are going to be harder then full race tires, for a couple reasons. This makes them less heat sensitive. It's not just that they are harder, the compound is made differently to have more consistant performance regardless or heat and wear. Wearas race tires are made for a very specific temp and load. If it's too hot out, or the load is too high, or they do not get the cooling necessary (closed wheel cars) then they blister. And if it's cold out, they have much much less traction. I think that R coumpound tires (having never driven them) are more stable, they react to heat, in the sense that they like it and have more traction, but I think it would be extremly hard to blister them. I also think that they may have similar grip when cold (well out of the range that they are made for) to race tires. Also, some of you may noticed that snow tires especially the blizzaks have a very soft compound, however, it won't heat up and become sticky like a race tire, in fact it has much less traction then the hardest touring tire on dry pavement, no matter what the temp is. It's more like foam then rubber, any chemical engineers herer that want to explain the difference? I did see a kid at the drag strip with blizzaks on the front of his cavelier or something. I think there is a material diference between race tires and street tires that makes race tires have a higher peak, but more sensitivity.

As far as heat cycles go, I would not be surprised that the thing about race tires that makes them sticky and peaky is also what makes them greatly affected by heat cycles. I don't think that R compound tires are going to be affected by that as much, but they still will be. Going along with what ace said, maybe the R compound tires have stronger bonds that allow them to wear longer and not break as soon, so technically you have to push them more to cycle them. However, with a regular street medium performance tire, the compound is harder, it has more carbon black in it (the stuff that makes it durable) and has stronger bonds that don't allow it to form to the pavement and therefore have less grip. I think it's just a nice transistion in compound from hard all-season tires to performance tires to R-compound tire to full race slicks. Each one has progressivly more oil and less carbon black and whatever else that makes it stickier and more temp sensitive. THe biggest jump is still between R and race slicks.
Has anybody noticed a difference in grip between cold all season tires and warm or even hot all season tires, I don't think I have. I think that's because their bonds are so strong and they have very little ooil content they just don't get affected by heat like that.
Also, tires loose the oil into the atmosphere whether they are being run or not, so I would say the older the tire the worse te grip no matter what tire. However, it affects race tires more since they have more oil and grip to loose and they probably loose it faster too.