Technical What is this on my brake disk??

[mzhussein]

i changed my engine mounts at the weekend, and notice this on the inside of my N/S brake disc....

Not sure what it is, and didn't have time to strip down the brakes...
when i run my finger over it it is slightly raised....any ideas??

 

[vladof]

What exactly do you see because it all looks normal to me.

The disk is only worn where the pad sits so it's pretty normal see it like that.

It would help if you could arrow point the exact place we should focus on.

 

[mzhussein]

on the brake disk, that black staining on the edge is what im worried about, its not on any of the other disks, it is where the pad should be making contact...the black is slightly raised, but lower then the "lip" at the edge of the disk...

 

[vladof]

It may be that the pad is of bad quality of so and is wearing the disk unevenly. Either that or something is permanently stuck in there or maybe the pad is not making perfect contact with the disk, which is unlikely.

I still cannot see exactly where the problem is, but if it's exactly on the edge of it I think it's nothing to be worried about.

 

[mzhussein]

the pads are EBC greenstuff, so deff not bad quality...its possible something is stuck between pad and disk...can you see the black mark all the way round the brake disk?this black is slightly more proud than the disk face, but not as proud as the outer lip...

 

[Davren]

The black band looks as though it's where the disc has rusted at some time and subsequently been rubbed off. Two possible reasons I can think of:

At some time in the car's history, someone has fitted pads with a smaller friction area which has allowed the black area to rust. Subsequently, the correct dimension pads were fitted which rubbed off the rust.

OR

Previous pads and discs have worn curved and the pads have been replaced but not the discs. Initially, the outer edge of the curved pad would not have touched the disc, allowing it to rust. As the new pad wore in, it would have rubbed off the rust.

Either way, it's not a problem now, but I would replace both pads and discs next time they're due.

 

[dave]

wall needs repointing

 

[mzhussein]

sounds about right...when i change the wheels to the schumi ones im trying to get hold of ill pop the caliper and have a look...i did replace the pads about 6 months ago, the old ones were the correct size/shape, so possibly curved disk...ill change em both when funds permit and ive got some life out of the pads...

@dave
It was rebuilt about 3 years ago by a family friend, who couldnt be bothered to point it after he done it....its quite annoying i took so many pcitures, and they were the best, the camera kept focusing on the wall through the wheels!

 

[vladof]

Maybe because it's the wall that actually has a problem not the wheel.

I think it's safe to say everything is well and no real issue is present.