There is a thread on this already, possibly started by me, but I can't find it. Michelin don't make PS4Ss in the standard 18 inch size for 575s. I have 2 questions: - is there any size of PS4S (not Ps4) that will safely fit the 18s on a 575? - Michelin say the PSSs that do fit standard 575s are not made for Ferraris but optimised for other manufacturers eg Porsche I guess. Is this a problem? Thanks.