Originally Posted by malter2.0
stretching a tire means you are placing tire thats narrower than recommended on the particular wheel width, not the other way around.
Correct. On camber limited cars like the e92 this is much less of an issue in the front than pinching a tire.
A 275 will work fine in the rear. By increasing the rear grip the car will put down power better but understeer more. Faster, but perhaps not as much fun.