Without brake dust shields (which smart says not to use), all Mercedes-Benz products get dirty wheels, especially the hard-working front disks. In the case of the smart, the rear brakes are drum-type and don't produce the dust that the front disks do. It is all a matter of the company that M-B sources their disk brake pads from. There are cleaner aftermarket alternatives, though some may have a lttle less stopping power or are noisier (squealing or chattering). Very hard compounds can score the disk rotors. It is all choices.