[LAP1DOUG]

Tire widths are not very uniform. That is some manufacturer's "275" may be closer to being a "285" or visa-versa. The bast way before you purchase is to compare data from TireRack.com, or from the tire manufacturer's site.

That said, on my 986S, I am running 285 rears with Hoosier A6's, which generally run quite wide. These are a 11.5" section width when mounted on a 10" wide wheel. I have not rolled my fenders at all and this works, but if I was lowered a bit more there would probably be some contact.

So, running a 285 is possible, but it depends on wheel offset, ride height, and suspension stiffness (max wheel movement).

Take careful measurements.