I have 9.5" rims, 19" diameter so no tire balooning, with 275 tires. That was fitted with springs in OEM position. I now have the lower Street Lynx rod instead of the spring, which would be good for another inch almost, probably similar to moving the springs inboard. 305 certainly, 315 maybe. It all depends on tire section width.
Above 17" should not be a problem, tire width is very close to tread width.
Don't take measurements from other people, measure your own car and be sure to do both sides. I did not have the same clearance on both sides, until I installed the street-lynx and really centered the rear-end.