Originally Posted by
DeadGrandpa
If it's a brake pad just barely touching the rotor, it might be because the piston isn't retracting all the way. You might remove the pads to clean them, and while you're at it, use a q-tip soaked with alcohol and clean the pistons so that any debris there will not impede the piston from retracting. You might even have to re-center the brake caliper. If that's off just a little bit, maybe not quite parallel to the rotor, that could cause a slight rub and consequent noise.
Nah. If the rotor is rubbing the disc, simply grease the rotor. The noise will go away. The issue is the rotor is dry. He needs brake grease. He can get it at any auto parts store. Apply liberally to the rotor.