you can only get the correct size Pilot Sport Cups on 19s (245/35/19 front, 265/35/19 rear). There are no tires (from Cups) that fit correctly on 18s. Track tires have very limited sizes.
2011 E92 M3 DCT
1991 Spec Miata
2008 E92 M3 DCT - KW Competition 2-way / Brembo 365 BBK / OMP ARS racing seats / rear seats delete / GT4 aero / AiM EVO4 data logger / SmartyCam racing camera
2008 E92 M3 6MT
2008 E92 335xi