Jack is right on here, that is what i have done as well. If the tires you buy are from a guy who knows how to ride, hopefully most of the tread that is missing due to shaving or wear is on the sides, leaving most of the meat in the middle...Free to $20 seems to be the going rate. One thing to look at is teh compound though. Dont get a qualifying tire and for sure don't get a rain tire. The Pirellis for example have SC1 Sc2 Sc3 and so on, the SC1 being super soft. The SC3 is labeled as Medium compound but is a very long lasting tire. If there are hard compund tires out there, they would be much harder to find.