Because your brakes, when applied, "straiten" the rotor (disk) from a cockeyed angle. To put it simply, your wheel bearings are worn and while driving, the rotor, wheel and tire are at a slight angle. The "wear indicators" (a small piece of metal attached to the pads on the top) built into the brake pads are temporarily rubbing against the rotor. When you apply the brake, it temporarily returns the group back to where is should be as if it were new, stopping the indicators from touching the rotor.
Thought i should add that if your wheel stops squeaking when you depress the pedal it is usually a sign of ball-bearing wear. The wheel will squeak through braking if the brakes are done, or worn.
That could be the brake pad "squealers". They are designed to squeal when they are worn out. Time for a brake job.
On all the brake pads which are made, they make them where they will begin to squeak if they need to be replaced. If they are squeaking then you need to get them checked immediately.
Answer: If its a high-pitched squeak, it sounds like the wear sensor on the inner brake lining.
Why do brake pads squeak after replacing pads?
When Exhaust brake is on squeak noise comes from the engine?"
No, rain does not cause brakes to squeak. Brake squeaking is typically caused by worn brake pads or a lack of lubrication on the brake components.
There is a small metal warning devise that rubs against the rotor when the pads are worn out. Replace your brake pads immediately. Failure to heed this warning will result in the rotors being destroyed.
Bike brakes squeak due to the friction between the brake pads and the wheel rim. This can be caused by dirt or debris on the brake pads or rim, misalignment of the brake pads, or worn brake pads.
Bike brakes squeak due to dirt, debris, or misalignment. To fix it, clean the brake pads and rims, adjust the brake alignment, or replace worn brake pads.
your e-brake is out of adjustment
Brake pads may be worn down to the brake "squealers".
Bicycle brakes squeak due to a buildup of dirt, debris, or worn brake pads. To resolve this issue, clean the brake pads and rims, adjust the brake pads, or replace worn brake pads.