you're driving a p38 if I recall. WHen I got mine, it had 19" wheels on, but i've swapped back to 16"
the approved options are 255/55R18 or 255/65R16
I dont know if 265/55R18 will fit the vehicle/wheel without issue but if it does, you'll see a very marginal speed decrease on your speedo (1mph @60mph)