that's a good question. i would definitely go with 225/40/18 if given the choice. but i just bought some wheels that came with 215/35/18 tires. these tires are practically brand new....so i would prefer to roll on them if possible, so i won't have to dish out $500 for about 6mm more sidewall.lilaznboi said:well, one thing, why on earth do you want to go 215/35?? that is such a thin sidewall you'll end up damaging your wheels a LOT quicker.