Your car gained 7mph .7 tenths from a 18'' tire to a 15'' tire? If so, i know whats the problem with my car, I have 18's all the round. Sick car!thanks for the compliments, i just picked up some skinnys looks like i will be saving 60lbs up front. the 18'' were 45lbs a side the new ones are only 15lbs.gonna try and get out one more time and if the weather holds might get down to atco for the buick vs ford event.