Uneven brake disc wear

[simonej]

I've already posted on the Chimaera forum but didn't get much of a response so thought I'd try here as well.....

I've just been removing the discs and pads for an inspection and found that the fronts have got some very uneven wear.

The outside edge is wearing normally but the inside edge doesn't look as though the pads are even making contact in places.



Compared to the outside;



The inside pad was almost rock solid in the carrier, in fact I had to knock it out with a hammer! There's a lot of corrosion and the pads do not seem to be free to move. Could this be the reason why it's not making proper contact or is there something else that could be wrong? It's already been suggested to grease the pins up but wondered if this was something anyone has seen before?

[paintman]

Assuming that your caliper is of the type with pistons acting on both pads then likely causes are:
1. The pad is a very tight fit in the caliper (some cheap pads are dreadful).

2. There is a lot of corrosion on the caliper preventing the pad moving which needs cleaning off
3. The piston(s) on the ineffective side of the caliper are seized or partially seized.

If the discs are badly pitted/worn consider replacing the discs while you are at it.

Edited by paintman on Wednesday 7th October 23:40

[GreenV8S]

Sounds like somebody may have replaced the pads without cleaning the carriers. The pads should be slightly loose in the carrier to allow room for expansion. If they're tight now they could get much worse when they're hot.

[Sam_68]

paintman said:

Assuming that your caliper is of the type with pistons acting on both pads...

I can't see the OP's photos because of our firewall settings in the office, but if they're standard Chimp calipers, they're of the sliding pin type and sticky sliders would be my first suspect.

As has already been suggested to you, strip them down and replace (or at least thoroughly clean and grease) the sliders and make sure the calipers are sliding freely and smoothly on their carriers, with no pads fitted.

[simonej]

Thanks for the input chaps. I cleaned the sliding pins as they were pretty tarnished and then regreased them. I also took a file to the carriers and got rid of all the corrosion - whadaya know, the pads now move freely!

Anyway, done a few miles in it today and the difference is immense. The brakes now feel very sharp and they lock the wheels with ease (not that I would ever want to obviously) which they have never done before. I'll remove the discs again when I get chance to inspect the inside edge and make sure they're wearing evenly.

[lenientism]

Make sure the pads are perfectly fit to the disc. It looks the inside pad can't make contact to the whole surface of the disc. You will find the brake works better if the disc is worn out evenly, and for the perfect performance it may need to clean off freckles on the inside disc using sandpaper.