well u can use 235 with 18inch tires but u need to have a 35 offset.. i know that i can run 225 tires on stock rims..

 

you go to www.tirerack.com and they say that you can run 225/45/17 on stock rims so i trust that website!

 

you CANNOT run a 225 on the stock rim safely, i really don't care what tirerack says. ask anyone who knows about tires and a 225 is way too big for a 6" rim. it creates a lot of sidewall flex and increases the chances of the tire seperating from the rim dramatically. a 215 is the widest that you should go on the stock rims, you really need a 7" rim for a 225 series.

 

So 18's are safe to run 225 on stock right, and 235's need a 35 offset. Thewheel I was looking at will be 18X7.5 on a 225/40/18 tire. They dont offer 235 anyway so I guess I'm good.