Chances are you've heard a squealing or squeaking noise while braking at some point in time. More often than not, this noise is an indicator of trouble. But there are a few instances where the squealing/squeaking or grinding is an unavoidable characteristic of a braking system.
The squeak or squeal noise occurs with front semi-metallic brake pads at medium speeds when light to medium pressure is applied to the brake pedal. Occasionally a noise may occur on rear brakes during the first few stops or with cold brakes and/or high humidity.
A grinding noise is common to rear brakes and some front disc brakes during initial stops after the vehicle has been parked over night. This noise may also occur due to trace amounts of corrosion on the metal surfaces during vehicle non-use.
It's normal to hear a small groan noise while stopping quickly or moving forward slowly from a complete stop.
So how can you tell if the brake noise you're hearing is serious or just normal? When the noise is continuous or persistent it's a good time to give your trusted mechanic a call. The squeal will usually indicate that the brake pads are in need of replacement. Grinding noises usually indicate a more serious issue. The cause of the grinding noise can be as simple as a small rock inside the brakes that needs to be removed. Or it could indicate that the brake pads have worn out completely causing the steel backing to grind against the brake rotor, resulting in a more expensive repair.