I'm looking into a M56x, but can't understand why you can't get the 20" rims or high spec brake pads on it. Does anyone know if there is some kind of physical limitation, or are they just figuring AWD means no fun.

 

high spec brake pads won't fit on the M56x brakes, only works for the sport brakes....

20" wheels won't work just due to them being summer compound tires.