FixedWing, In the 18" Cup series Michelin does not make anything bigger than the 295/30ZR18. You did give me another idea. Pirelli, in the Corsa series makes a 315/30ZR18 which has an outside diameter of 25.44 inches and a tread width of 12.4 inches. They also make a 265/35ZR18 Corsa. It has an outside diameter of 25.35 inches and a tread width of 11.10 inches. Another match! Now I am really confused.

Pirelli P Zero Corsa
265/35ZR18 25.35" OD, 11.10" tread width
315/30ZR18 25.44" OD, 12.40" tread width

Michelin Pilot Sport Cup
265/35ZR18 25.2" OD, 10.9" tread width
295/30ZR18 25.1" OD, 11.6" tread width



Oh so many choices. Which is the right one?