The wheels get dirty because of the brake pad compound specified by the TUV, which is the German authority which sets German vehicles regs, and tests products to ensure they meet those regs. You can switch to pads made by Porterfield, Mintex, Pagid, or EBC. They all produce much less dust. Some people report that they squeal more, and that the EBC's cause excessive rotor wear.
For tips on washing, waxing, polishing etc., try www.autopia.com
For tips on washing, waxing, polishing etc., try www.autopia.com