A FRESHLY PAINTED WHEEL IS MUCH EASIER TO CLEAN. THE COMMERCIALLY AVAILABLE WHEEL CLEANERS ARE USUALLY ACID BASED AND DESTROY THE PAINTED SURFACES AS AGGRESSIVELY ASTHE DUST IT SELF DOES WHICH IS ALSO ACIDIC. P21S IS ONE OF THE MILDER CLEANERS BUT I HAVE SEEN IT DAMAGE SURFACES IF SPRAYED ON TO HOT WHEELS OR LEFT TO DRY . IDEALLY ONLY AUTO CARWASH SHOULD BE USED TO CLEAN THE WHEELS. YOU MAY JUST NEED TO DO IT MORE OFTEN. I HAVE USED KLEEN WHEEL DUST SHIELDS FOR YEARS ON MY 560SEL AND OTHER CARS WITH GREAT SUCCESS. I DO NOT KNOW THE TRUE FORMULA FOR WHY SOME PEOPLE HAVE BRAKE PROBLEMS WITH THEIR USE. THE LOCAL MB DEALER SELLS THEM. I SHOULD PROBABLY BE THE EXTREME CASE OF ABUSE ON BRAKES AS I SOME TIMES BECOME CONFUSED THAT I AM IN MY PORSCHE RACE CAR RATHER THAN MY WIFES BENZ. (SHE DRIVES LIKE A MANIAC ALL THE TIME, HER FAVORITE SAYING IS "IF YOU DON'T LIKE MY DRIVING-GET OFF THE SIDE WALK"). IF NOT TOO MUCH DAMAGE HAS BEEN DONE TO THE WHEELS ALREADY WHERE REPAINTING IS REQUIRED, TRY THE SHIELDS.