Grinding noise coming from the rear brakes.

[Jonny88]

Hi all,

Recently I've noticed a grinding noise coming from my rear brakes when braking.

It sound very much like the noise you get when braking after the car has been stationery and has a build up of surface rust on the discs, except louder. However, the noise is occurring randomly throughout journeys (not just at the start as you would except with the build up of surface rust).

The weight of my braking, vehicle speed and weather conditions seem to have no relevance to the occurrence of the noise, however it is easier to hear when the car is moving slowly as there is less noise from the road and passing air. The noise seems to be coming equally from both sides of the car but it is difficult to tell accurately.

I'm far from a trained mechanic, but on initial inspection of the discs, they don't seem overly rusted or worn. More difficult to tell with the pads without getting the wheels off.

Has anybody else experienced this or have any ideas as to what might be causing the noise?

Many thanks,
J.

[Crasher]

It could be poor quality pads.

[mkman1]

You need to jack the car up and turn the back wheeels with your hand and see if you can hear any noise. Listen out for noise from the wheel bearings. Also turn the wheel as fast as you can an dthen get someone to appy the foot brake, and then see there is a noise. If you cannot here any noise the you will have to get some to sit in the car and see they can hear anyting when you drive the car.

You will have to inspect the pads and disc as soon as possible.

[Jonny88]

So, the noise is coming from the rear nearside wheel only.

Had the car jacked up last night and took the wheel off. Photos attached.

When I spun the disc freely there was a grinding noise that I expect is responsible for what I'm hearing when braking (except louder when I'm braking due to the additional force). Having jet washed the pad and disc, initially it seemed better but having driven it since it's no better unfortunately. When I spun the wheel gently, it completed many revolutions before stopping, indicating that the resistance isn't that great.

Could it just be something stuck in the pad that is creating the noise when making contact with the disc? How technically challenging is it to get the pads off to inspect?

Thanks,
J.

[Crasher]

You need new discs and pads, you have a corrosion lip.

[Jonny88]

You need new discs and pads, you have a corrosion lip.

Thanks Crasher. What is a corrosion lip and why would it suddenly start making the noise?

[Crasher]

The pads do not sweep the full area of the discs and consequently a lip of corrosion builds up on the disc above and below the swept area and eventually this starts to disintegrate and expand to such a degree that it can rub on the pad backing (when the pads are getting low) which can make a terrible and it can even rub on the pad/caliper carrier in extreme cases.

[Jonny88]

I noticed today that I can hear a brushing noise when free wheeling and then the full grinding as I brake. Does this indicate that the situation is worsening or could it just be a side effect of the grinding?

I'm going to tackle changing the discs and pads at the weekend. Is there a specific caliper rewind tool required or will a generic one suffice? Are the rears left or right hand threaded?

Thanks.

[Jonny88]

So it turns out that the friction part of the brake pad had delaminated and disappeared completely. Subsequently, I had been braking on the metal part of the brake pad and having worn that down, completely buggered the caliper piston.

2 x rear pads, 2 x rear discs and one rear caliper later, my wallet is 300 shreddies the lighter.

Lesson learnt: don't ignore funky noises coming from the brakes and get them sorted sooner!