Hey all,

I have a Trek 6500 with Hayes disc brakes, and over the last month my front disc brakes make a humming, oscillating sound when I ride at medium speeds. When I ride at low speeds or test the wheel when the bike is in a stand, I get no sounds, nor do I get any humming sounds when I am riding the bike very fast. It also occurs more frequently if I am turning.

This sound only occurs at medium speed. It sounds like a metal-on-metal sound, but I can't figure out what is causing this since it is only under limited circumstances. I have inspected the rotors and the disc pads and they do not appear to rub in any one place.

Does anyone have any guesses what is causing this? It is hard for me to tell if it affects the performance of the bike, nonetheless the sound is quite disconcerting.

Thanks very much for your help.

-Mark