I have that issue. I sanded the rotors and the brake pads and it is still there. I even upgraded the brakes from Hayes to Shimano Deores(Not rotors) and still have the hum. I have concluded that they are the Hayes Rotors. I can live with the hum, but when it is time to replace them, i will be getting some Shimano rotors..more than likely the ICETECH rotors.