Not official but general rule:
<350hp = 255's
350 - 419 = 275's
420+ = 285's+

The wider you go the slower you'll go in a straight line, however with the added power it multiplies and ends up the same.

 

mike01...your setup...do you think you have enough room on the inside and outside for 275s?

 

Nice!

 

For the fronts I would say yes, for the rear I would say the fenders would have to be rolled for 275's. I mean my 255's cleared by a C-hair if you know what I mean...lol

 

hmmm
my 255s fit front and rear with alot of clearance but they wont fit in the fronts without a good stretch on the fender and the rears will need a little roll...but 255s in the rear have alot of clearance
i might pickup a set for 275 use

 

FYI, these wheels do not fit Ohlins coilovers in front without spacers. I just got a set. It's not a matter of tire clearance. The rim hits the spring perch in front even without a tire mounted on the rim. I'm using a 15mm spacer which gives decent clearance for both the rim and a 255 tire, but there's still less than a pinky finger's clearance between the tire and the spring.