1. Consider demounting the front tires and check for any wheel weights or old valve stems inside. Alternatively, try rotating the tires rear to front and listen for any change.

2. Retorque the bolts joining the front hubs to the rotors.

3. Retorque the caliper attachment bolts.

4. Retorque the wheel lugs.

5. With our non-floating calipers, if there is excess clearance between the caliper piston and caliper body, the piston may "rock" or chatter, inducing a noise coupled through the rotor/hub assembly. When brake pressure is applied, the clamping effect between the piston and rotor effectively eliminates any clearance. This is a remote possibility since you do not describe any pulsing sensation through the brake pedal.


Good luck with your troubleshooting effort.

__________________
Blair Tyson
1985 300D
300,000 + miles