From BMW M Registry:
What are the factory wheel and tire sizes for the F10 M5?
The F10 M5 is equipped as standard equipment with 19-inch "Style 345M" cast-alloy M Double Spoke alloy wheels. These measure 9.0 x 19-inches in front (with 265/40ZR19 tires) and 10 x 19-inches in the rear (with 295/35ZR19 tires). Larger BBS-made 20-inch forged "Style 343M" M Double Spoke alloy wheels, measuring 9.0 x 20-inches in front (with 265/35ZR20 tires) and 10 x 20-inches in the rear (with 295/30ZR20 tires) were offered as an extra-cost option. These were alternatively offered with a black finish in some markets. M5s equipped with the optional Competition Package include unique 20-inch "Style 601M" M Double Spoke cast alloy wheels. However, in many markets the Style 343M wheels could be specified with the Competition Package as a no-cost option.
http://www.bmwmregistry.com/model_faq.php?id=54