bigger wheels actually do make you lose hp. but they were using a dx civic motor and made the huge jump from 15 to 17 inch tires. lost about 8-10 i think. On my turbo honda prelude it had 17's and switching to 16's made no difference, but using a better tire made a huge difference. For example i would always beat my friends turbo integra until he got falken azenis tires and he would take me everytime by a car or 2.