Question: My brakes are squealing. Does that mean I
need a brake job?
Answer: Not necessarily. A certain amount of brake noise
is considered "normal" these days because of the harder
semi-metallic brake pads that are used in most front-wheel drive
cars and minivans. This type of noise does not affect braking
performance and does not indicate a brake problem. However, if
the noise is objectionable, there are ways to eliminate it.
Brake squeal is caused by vibration between the brake pads, rotors
and calipers. Pad noise can be lessened or eliminated by installing
"noise suppression shims" (thin self-adhesive strips)
on the backs of the pads, or applying "noise suppression
compound" on the backs of the pads to dampen vibrations.
Additional steps that can be taken to eliminate noise are to resurface
the rotors and replace the pads.
Some brands of semi-metallic pads are inherently noisier than
others because of the ingredients used in the manufacture of the
friction material. Strange as it may sound (pardon the pun), cheaper
pads are sometimes quieter than premium quality or original equipment
pads. That's because the cheaper pads contain softer materials
that do not wear as well. For that reason, they are not recommended.
Premium quality pads should cause no noise problems when installed
properly and will give you better brake performance
and longer life.
Conditions that can contribute to a disc brake noise problem include
glazed or worn rotors, too rough a finish on resurfaced rotors,
loose brake pads, missing pad insulators, shims, springs or antirattle
clips, rusty or corroded caliper mounts, worn caliper mounts,
and loose caliper mounting hardware. Drum noise may be due to
loose or broken parts inside the drum.
Most experts recommend new caliper and drum hardware when the
brakes are relined, a thorough inspection of the calipers and
rotors for any wear or other conditions that might have an adverse
affect on noise or brake performance, and resurfacing the rotors
(and drums) if the surfaces are not smooth, flat and parallel.
If you hear metallic scraping noises, on the other hand, it usually
means your brake linings are worn out and need to be replaced
-- especially if your brake pedal feels low or if you've noticed
any change in the way your vehicle brakes (it pulls to one side when
braking, it requires more pedal effort, etc.).
Some brake pads have built-in "wear sensors" that produce
a scraping or squealing noise when the pads become worn. In any
event, noisy brakes should always be inspected to determine whether
or not there's a problem. And don't delay! If the pads have worn
down to the point where metal-to-metal contact is occurring, your
vehicle may not be able to stop safely, and you may score the
rotors or drums to the point where they have to be replaced.
