would i notice any negative impact if i went from the factory 17" wheels on my 2005 sedan with 235/50/17 tires, to a set of factory 18" wheels off a coupe, with 225/45/18's in front and 245/45/18's in the rear? other than financial? someone is selling a set of rims/tires off their coupe and they have about 5200 miles on them. I thought it might be a cheap mod if it won't cause any problems with the ride/balance of the car.

also, do i have to have two different tire sizes? could i eventually replace them with all the same size? say the 245/45/18's. thanks.