Originally posted by johnc:
Why don't you use your stock wheels for track events and keep the nice wheels for the street? Put a set of 225/50-16 Kumho V700s or Toyo Proxis RA1s on the stock 16 x 6.5" wheels. Both of those tires will stick a whole lot more than anything suggested so far.
I second this. Once your OEM tires wear out at the tack, you can get much lower profile tires (who cares about speedo when racing?) to increase grip. Also, get dedicated track tires (autocross, road course). Despite looking like they have less tread, they will last longer at the track than street tires. It'll be cheaper to replace 16" race tires than 17's.