until I changed over to "Metal Master" brake Pads from "PBR". When I had the original brakes on the car, I had to clean the wheels every 1-2 weeks, and with those numerous cross spokes, are a pain in the ass to clean. Now I'd drive the car for a month and I could barely see a change in color on the wheels. I am having the same problem with my '99 540i and am changing over to Metal Master soon. I expect to same result since the are made of the same materials. I got mine from Bavauto, but other online stores carry them too. Hope this helps.