BMW 640i Loud noise is coming from rear brakes Inspection at your home or office.

Common reasons for this to happen:

• Worn Brake Pads: Obviously, the most common potential problem here is worn out rear pads (or shoes if you have drum brakes). If you notice a loud grinding sound, it could be the metal backing plate from the pads making contact with the rotor.

• Broken or Missing Caliper Bolt: Your calipers are essentially two halves held together with bolts (not the slide pins). If one of the bolts is missing or broken, it’s possible that part of the caliper has popped out and is making contact with your wheel.

• Contact with the Squealer: Squealers are metal tabs designed to lightly contact the rotor and create a noise that warns you the pads are wearing down. If your pads are nearing the end of their life, it’s possible this is the noise you’re hearing.

• Parking Brake Shoes Stuck: Your parking brake is located in the rear of the car. In a disc brake setup, there are shoes located inside the inner drum built into the rotor. If the shoes are stuck, it’s possible that the sound you’re hearing is them contacting metal while you’re driving.

• Wheel Bearing Failure: If the noise you’re hearing is a “howl” and it’s constant, the first thing to suspect would be one of the wheel bearings (whichever side is the loudest while you’re driving).

• Pads Settling into Place: If the sound you’re hearing is more of a “pop” or a loud click, it might be nothing more than your brake pads being slightly worn and settling into place when you push the brake pedal.

• Normal Pad Vibration: If you only hear the noise when you’re backing up, it’s possible that it is just a normal vibration caused by the friction material of the pad lightly contacting the rotor’s surface. This is called “resonant frequency”, and can occur with both disc and drum brakes.