On my first Spyder I changed the rear tire at 12,000 miles because I was leaving on a long trip and did not want to have to find one out-of-state somewhere. The tire could have gone further. I replaced the tire with another Kendra tire, which lasted 22,000 miles (over-due when replaced). At 34,000 miles I install a B.F. Goodrich gForce Sport. At 36,500 miles the Spyder burned to the ground.
On my second Spyder I replaced the rear tire at 18,500 miles with a B.F. Goodrich gForce Sport 225/50R15. I have about 16,000 miles on the gForce and it is looking really good. The wear pattern is perfectly even and it is obvious the tire will greatly outlast the OEM tire. I could not be more pleased. The gForce currently sells on TireRack.com for $92.00 plus freight.
I am also running auto tires on the front of the Spyder.