Brake dust on 2009 Chrysler Town & Country

Since new I have had 3 times the brake dust on the rear wheels compared to the front.The dealer ,in response to a high speed braking vibration, has re surfaced the rear rotors twice,new pads once and replaced the front rotors. They will not address the brake dust though. What could be causing it? It looks terrible in 200miles.

Asked by for the 2009 Chrysler Town & Country
Regular brake pads can be quite dirty as they wear, next time have them install ceramic pads and your wheels will stay cleaner longer