Originally Posted by scottIN

Depends on how fast you want to go. They'll start to go off after about 15-20 miles. If you're racing a the national level, you change every race-although some sanctioning bodies limit the number of tires per weekend to keep the cost down. Since I just race club races, I usually get 200+ miles out of them and run them down to the cords before I get new ones. Times do drop off, but the .1 or .2 I lose from old tires is nothing compared to what I lose in driving mistakes. If you're racing at the national level and don't make driving mistakes, that .1 or .2 is worth it.

It's not been as fruitful in the last few years since the sanctioning bodies started limiting tires, but we used to go dumpster diving for tires after the national races. You could find tires that had 12 laps on them that the big teams just tossed out. Perfect (and free) for club racing or practice.

Tires run about $190 / set.

It does feel sooooo good to run the first time on a new set of tires though. There's so much grip that if you're set up a little tight, they'll turn so hard it's actually painful.