Customer’s concern: “My brakes make a squealing noise sometimes when I
apply them lightly at low speeds; when I apply them with more force, the squealing stops.”
What’s happening and why: As described in some owner’s manuals, the
squealing noise is caused by high-frequency vibration of the brake pads against the
rotating brake disc. Vibration is the unavoidable result of friction generated by the
pads as the caliper clamps them against the rotating disc. Under average braking
conditions, some brake noise is normal and cannot be eliminated.
Normally, the shims and the high-temperature grease between the pads and the
brake caliper dampen and isolate most of the vibration. the level of vibration,
however, is affected by outside temperature and humidity, by road conditions
(mud, dust, and road salt), and by the condition or thickness of the brake pad material.
What can be done: If the squealing noise is abnormally loud, have the brakes
inspected and checked for pad wear.
• If thickness of the friction material (compared to the wear indicator)
indicates that the remaining usage lining won’t last until the next scheduled
service for the vehicle, then replace the brake pads.
• If enough friction material is present on the brake pads, then replace only
the pad shims and the high-temperature grease.