I believe they are the same on the C7 Grand Sport. Mine are Michelin Pilot Super Sport Run Flat 335/25ZR20 (rear) I did nt go for the 707 package so they may be different if you ticked that box.
I've got the Z07 package and the tyre size is the same
Luckily I don't need any, but I thought I'd have a look anyway, and it seems Black Circles now stock both front and rears of the correct size Michelin Pilot Super Sports in case anyone is needing to find them.
