ok i seem to be in a jimmy lol...ok i want to upgrade my rims to 18 inch..but i have not seen anyone on here ask how this will affect your cars ride? and tranny? and will i have to reprograme my cars computer to the 18s.so the speed o is reading right and my gears are switching right....so i hope with the replys this will help other people to instead of people saying yea they will fit lol... i am a NEW g6 owner :) i have a 06 sedan...thanxs for any help site rocks \nn/ p.s what size tires sould i get??

first of all what size tires and rims do you currently have? if you want to go to 18s all you gotta do (after makeing sur you get wheels with the correct bolt patern and offset of course) is find a matching tire to your stock size. changeing wheels has nothing to do with the transmission. if you find the right tire size you will not have to have your speedometer recalibrated.

for instance, my car came with 17" wheels with 225/50R17 tires, and i later bought stock 18" GTP wheels and am running tires that are 225/45ZR18 and they are just about the exact same diameter and overall height as the stock tires on the 17" wheels. the 45 is a wee bit lower profile than the 50 on the stock 17s but because of that my car handles a bit better, and my speedo is still accurate.

here is the tire calculator from discount tire:
http://www.discounttiredirect.com/direct/brochure/info/tmpInfoTireMath.jsp

thanxs for the reply yea i understand all of that..what u where saying about geting closest match to your stock tire and rim just was not all sure if i would have to recalabrate..does any one no a good site that sells chrome 18 inch rims and tire packages?? my g6 is silver so i think i will do it in chrome make it classy lol..