It's pretty obvious that in the rear I wouldn't be able to fit more than a 275. The front on a +12 wheel surprised me. I didn't figure that a fender roller would stretch the fender out that much. Although, my car is pretty low as is.
I'm thinking about upgrading at least tires in the near future, if not wheels too, but to play it safe I may end up going with a 265/35/18 as I want to reduce the likelihood of rubbing altogether.