The only time i ever had an issue with the 18X8's on the back of my GXP was the camber. I went throught the trouble of installing cam bolts top and bottom to correct the common trouble and wound up skinning the sidewalls on both tires. I was taking some friends to the airport with all their luggage and encountered a rubbing noise in the rear, got to the airport to find what looked like spaghetti hanging off my sidewalls. The lip on the inside of the rear quarter was the culprit.
Lesson focus: Leave a little neg camber to insure the tires clear the lip of the rear quarter.
