I'm looking at buying new tires this summer, the ones I have won't last too much longer. I currently have a set of 20" CS67 rims that came with the car. The problem is that I don't know the width on them, not sure if they are 10 inch or 9 inch. What do I need to do to find out? I have 265's on the front and 275's on the back, if that helps.

 

The size is stamped on the inside (back) of the rim.
Pull a front and rear to see the stampings...
265s fit nicely on 9" wide rims as do 275s.

 

personally for the back i like a real meaty tire so i would go with 295 on a 9inch rim and a 315 or bigger on a 10 inch.