its not just the size of the wheel, its also the size of the tyre u put on the wheel, for instance, my car has 185/60/13s and hav just got sum 14s to put on, if i put 185/55/14s on then the outer diameter of the two different wheels are almost identical so wont effect performance. they are actually 0.2% bigger so wen the speedo says im doin 60. i wil actually be doin 60.8 or summet.
sorry for the esay lol