||The hang-up is going to be the lower control arm and HICAS knuckle (if TT). With a 17" wheel, the wheel/tire will contact the LCA earlier than with an 18" wheel. The widest I have seen is 295s on an 18" wheel, with a fender roll, and no LCA modification (you might be able to squeeze a 305 though).
If you modify the LCA, you can fit 315s.
I'm sorry I don't have more info about 17" wheels.