Why brakes make grinding noise?
Brakes can squeal and screech, and while it’s annoying, most drivers ignore it. But when brakes make grinding noise, drivers take it seriously. And they should because it’s the sign of serious brake problems.
There are many causes. Here are the top 4
1) Metal to metal contact. Friction material is worn out and the steel brake pad backing plate is rubbing against the rotor face.
2) Brake pads have failed due to overheating and glazing and friction material break-up. If the friction material has lost its grip with the steel backing plate causing it to crack or break off. All of these conditions result in excessive vibration when applying the brakes and that comes across as a grinding noise.
3) Excessive vibration due to uneven brake pad application. The brake pads must apply and retract smoothly in their guide areas. Corrosion buildup that prevents the pad from moving or retracting freely will result in a sticking brake that applies uneven pressure against the rotor, decreasing braking power and causing that portion of the friction material to overheat.
Brakes make grinding noise when there’s metal to metal contact
In normal operation, the brake friction material is pressed against the brake rotor. But when the friction material wears off or breaks off because the adhesive has failed between the material and the steel brake pad backing plate, the backing plate itself is pressed against the rotor. That results in metal to metal contact that causes an awful grinding sound. The images below show what can happen when a backing plate with absolutely no frictional material is pressed against the rotor.
Metal to metal contact wears off the surface of the rotor and destroys the brake pad backing plate.
The Fix for metal to metal contact
Replace brake pads and rotor with high quality parts. See this post on how to shop for high quality brake pads. Clean all contact areas and replace all brake hardware including anti-rattle clips, shims, caliper slide pins and boots. Use high temperature synthetic brake grease.
Brakes make grinding noise when the brake pad has failed
Brakes make grinding noise when the brake pads are seized
When brake pads can’t move freely in their slots, they apply unevenly causing a grinding noise due to excessive vibration.
The binding can cause only the top or bottom curved edge to contact the rotor. Or, corrosion can cause the top or bottom end, or “ears” to bind, causing brake pad taper. Either way, only a portion of the brake pad contacts the rotor, causing excessive vibrations that sounds like grinding.
Brake pads can also fail due to substandard steel backing plates that flex during application. This causes the edges of the pad to delaminate resulting in edge lift. This introduces another vibration point that can cause the brakes grinding sound.
The Fix for binding brake pads and delamination
All economy and some “OEM” brake pads are made with substandard steel backing plates that are painted. Eventually the paint degrades and the steel rusts, causing the friction material to debond.
Brakes make grinding noise when the caliper is seized
Floating calipers must slide easily along the caliper slide pins or they will not apply even braking pressure to the brake pads. Caliper slide pins can corrode and stick the bores, preventing the caliper from applying and releasing properly.
Partial application of braking pressure can a brakes makes grinding sound condition.
The Fix for seized brake calipers
If the caliper slide pins are corroded, replace them along with the degraded rubber boots.
Brakes make grinding sound due to improper bedding procedure
Most newer brakes are adherent versus abrasive style which means they continually deposit a sticky film on the face of the rotor. When you apply the brakes, the friction material contacts the sticky film which converts rotary motion to heat to stop the vehicle.
New brake pads must be “bedded” to the rotor to apply an even film coating on the rotor face. Every manufacturer and every type of pad has its own bedding procedure. If done improperly, you can actually create excessive vibration that sounds like grinding because you’ve deposited too much or too little of a film layer.
The Fix for improper bedding
Using 150-grit sandpaper and a random orbital sander, sand the rotor face on both sides to remove brake pad film buildup.
©, 2019 Rick MuscoplatPosted on by Rick Muscoplat