Standard sizes are 265/35/19 and 245/35/19 - usually PS2's
I'm running 275/35/19 and 255/35/19 Vredestein Ultrac Sessantas.
These, for me, are a good balance of performance & budget - I do a lot of motorway driving. They're a capable tyre and reportedly better than PS2's in the wet.
Had this set on for 20k miles - rears will need changing soon, but the fronts are ok (yeah, yeah, M3 fail
Most wouldn't advise mixing different tyres front & rear.
E92 M3, Jerez Black, Fox Red Novillo, 19'' M Double Spoke, folding mirrors, lumbar support, front seat heating, PDC, USB, DAB, EDC, Bluetooth, Logic 7, High Gloss Shadowline, big smile