rims.. they aren't there to make wheels same size as stock... either way i have the tire rack sizes and have no problems whatsoever (front: 245/40R18 Rear: 275/35R18).. you're forgetting one key factor though that does affect the overall tire size.. it's the width of the rims... I have 275's in the rear on 8" rims which makes the sidewall noticably larger...