Grinding noise when braking is an indication of excessively worn brake pads for disc brake type or excessively worn brake shoes for drum brake type.
Car Trouble Symptoms
Well, grinding noise when braking occurs after the brake pedal is pressed. Grinding sound or grinding noise is usually heard by the driver coming from either the front or rear brakes.
Grinding noise when braking is also known as brake groan from a technical point of view is the noise caused when metals are rubbed together. The noise occurs when the metal base of the pad is rubbed together with the rotor when the pad is worn out completely. If you heard a loud grinding noise when braking while depressing the brake pedal, it indicates worn-out brake lining that’s rubbing against the vehicle disc or drum.
You may have been ignored your brake too long that’s why you do not know that it had been worn out, up until you notice a grinding sound while braking. If it’s ignored for a long time it could be costly to repair it.
Grinding noise when braking possible reason
(1) Excessively worn brake pads.
(2) Excessively worn brake shoe.
(3) Rust, flaw and dust on sliding surfaces of the rotor
Car troubleshooting
This indicates poor maintenance of the brake, probably the brake has been neglected too long that’s why the pad is worn down to the metal.
Depending on what brakes are affected, the front or the rear the reason for grinding noise is the brake linings (pads for the disc brake usually on the front brake or shoe for the drum brake, usually on the rear.) worn out to the extent that the metal portion of the linings is rubbed against the rotor or the dum, every time the brake pedal is pressed during applying the brake.
However, not only an excessively worn lining can cause grinding noise, rust, flaw, and dust on sliding surfaces of the rotor and drum can cause a rubbing noise which is similar to the noise caused when metals are rubbed together. The noise occurs when the metal base of the pad is rubbed together with the rotor when the pad is worn out completely.
What to do?
Fixing grinding noise problem depend on the cause and the extent of the problem. If you don't have knowledge of automotive and don't want to do the work of fixing your car, better to bring the car to a reputable repair shop that specializes in brake repair, tell the mechanic to inspect the brake where the noise occurs (front or rear brake), then depending on the cause of the problem and the extent of the damage because of the problem, the worst case is you need to have the rotor or the drum machined including the replacement of brake linings on the affected brakes.
To fix the problem, first, replace the brake linings, then depending on the damage, based on the advice of your mechanic, if it is extreme replace the disc or drums, if it's not, the discs or drums must be machined to smooth out the damage caused by the worn-out linings, repair only the affected portion where the grinding sound is coming (front or rear).
Now, if you want to do the fixing by yourself, the first thing to do is to inspect the affected brakes, refer to the service manual of your car model on how to inspect the brakes. If the brake pad is good then the grinding noise is not caused by excessive pad wear.
Clean the disc brake rotor and pad, because wear powder of pad, etc. on the brake rotor can cause abnormal noise. It is also effective to make a slit in the disc pad to prevent wear powder of the pad from adhering to the rotor.
Slit cutting method
Draw a line at an angle of 35 to 40 degrees from the pad’s centerline as shown in the figure below and cut a slit with a hacksaw. The depth of the slit should not exceed the wear limit. The width of the slit should be equivalent to a thickness of about three cutting blades together.
However, if the brake linings are excessively worn out to the metal, replace the linings of the affected brakes. check the brake rotor or the brake drum for any damage and bring the parts to the machined shop to have them machined.
How to prevent grinding noise when braking
Always follow the maintenance schedule recommended by the car manufacturer, most of the time the maintenance schedule can be found on your car owner's manual or the service booklet.
If you notice an abnormal sound coming from your brakes, never neglect it, have the brakes checked by a mechanic the soonest. The brakes have what is called a "brake wear sensor", it can either be mechanical or electrical type, it's the thin metal connected to the pads.
When the brake pads are worn out, these thin metal plates make contact with the disc and will produce squealing noise, it's used to warn the driver that the brake pads are needed to be replaced. The purpose of this sensor is to warn the driver that the brake linings are worn out. When the linings are worn out, the brakes make noise usually a "squeal noise" so if you heard this noise have your car brakes checked by a mechanic.
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