Man, with the 295/30's going for about $381 a pop, the 315/30's will likely cost low $400's each

 

235/315 requires wider rear wheels and rolling rear fenders. Heavier , wider rubber also means slower straight line acceleration and longer stopping distance due to increased rolling resistance, drag and inertia .

 

I believe 315's will fit on stock 11" rims without rolling the fenders. Rosso 315's seem to fit on my car OK. They slightly rub on the inside plastic fender liner.

 

315s fit fine. The benefits of wider rubber outweigh the "negatives" you mentioned. In my experience braking is actually improved with wider rubber because there is more contact patch.

 

I had the 315 rear and 235 front Michelin PS2 tires installed today. The ride is extremely comfortable and quiet. In the limited time I have used these tires, it appears that the car is quieter than with the regular Pilot Sports(315/235) or the P Zero(295/225) that I have previously used....certainly no worse and turning response is very crisp and improved. There are no rubbing issues, the fenders do not require rolling. Originally, I was going to go with the 295 rear and 235 front, but became skeptical after reading comments on the boards. I decided to use the 315 rears, since they are a perfect match for the 235 fronts. The 295 PS2 tire diameter is considerably different than the 235 PS2 and given the turbo's AWD system, I decided not to take a chance of prematurely wearing or overworking the drivetrain with a mis-matched set of tires.

You can see the difference in the tire diameters below. Notice what a perfect match of "Revs per mile" the 235/315 combination offers....

PS2 315/30ZR18 = 817 Rev pe mile
PS2 235/40ZR18 = 819 rev per mile

VS.

PS2 295/40ZR18 = 832 rev per mile
PS2 235/40ZR18 = 819 rev per mile

 

Thanks for the helpful info John D II. I have this combo in mind also! Keep us informed if anything changes!