if you ran the tires that are on the bike right now, at the track, there's your problem. Track pace will KILL a set of street tires in a hurry. All the "preservatives" in the rubber that keep them from rotting away will actually boil out of the rubber. You'll notice alot of "blueing" of tires after they're been on the track. That's b/c they got HOT. Hence why racer's and track junkies sell thier take offs, still with plenty of tread, to people NOT on the track. They know they tires are shot, tread depth be damned. At a "normal" (read: LEGAL) street ride, it's not really that big a deal, but the more you push it with a tire that's been heated like that, the more likely you are to get 'em spinning, especially if it's colder outside.