Rapid, uneven rear pad wear

[aesmith]

Hi,

I've just had to replace the rear pads after only about 6 or 8 months (say no more than 7,000 miles). Two things strike me, firstly that seems a very short life, what sort of mileage to others get? Every time I've checked the wheel turns freely with no binding, also checked by feeling the disc after a journey and it's never more than very slightly warm.

The other thing is that the pad wear is not even, the pad on the piston side is much more worn than the other side. It seems to me that this means the caliper isn't sliding properly, but I can't feel anything binding when I removed and refitted the caliper. Could there be something worn that means the caliper feels free to slide, but doesn't actually do so in real use?

Pointy S K6.

Thanks, Tony S

[Nutsinatin]

Depends how much you use your rear brake but I replaced my rear pads when they fell apart, was nowhere near wearing them out (they had been in the bike for 5 years so 28,000 miles with 20,000 of those being me in the last year).

[NTECUK]

JP used to muller his pads looked at loads of times.
When he got it mot test they failed the stop light of the rear brake.
Next weekend when you followed him he road with the foot just resting on the back brake!
I didn't take the rise..... Much lol

[NTECUK]

Hi,

I've just had to replace the rear pads af

The other thing is that the pad wear is not even, the pad on the piston side is much more worn than the other side.

Thanks, Tony S
Check out the side play on the axle.
Spacers and incorrect fitting of calipers and there mounts does happen

[andrewsmith]

Tony

Yours is a curvy?

[aesmith]

Tony

Yours is a curvy?

Pointy.

I think NTECUK may be on to something. I'll check the spacers/washers on the back.

Tony S

[Bibio]

what make of pads did you fit?

[aesmith]

what make of pads did you fit?
The pads that have just worn out were EBC GG.

[keith_d]

When you fitted the new pads was it relatively easy to slide the pistons back into the caliper? If one of them was sticking it could result in the pads resting on the disk.

[Bibio]

those should last 20k+ miles.

if its just the piston side then i would suspect that your calliper needs a proper service.

[aesmith]

Last two comments. It's only a single piston in the rear caliper. I would have to admit it could be better, but when you release the brake pedal the piston clearly retracts a couple of millimetres. Also the wheel is free to turn by hand, and the disc doesn't get hot in use.

If the caliper piston was sticking, shouldn't both pads wear?

[NTECUK]

He did say in the op it's ok.
Hopefully he did check out all of the movement.
When mine stuck zx6 it soon got the disc warm.

[NTECUK]

If the slider sticks it will wear the pad on the passive side and often wear it in a wedge profile

[Bibio]

its not the piston that is sticking. the sliders might look ok but in use they might actually be jamming. this would wear the piston side down due to the piston being free to move and the sliders not.

this is why i said service 'properly' the calliper.

[aesmith]

this is why i said service 'properly' the calliper.
I think that's what I need to do. When it was apart in the Autumn I didn't have the piston out, and it wasn't as free as I'd ideally have liked, but looked "OK" as I could see it retracting and feel the wheel freeing. The sliding mechanism was completely free, and still is. However something's not right, or maybe two things. If there's a spacer or washer misplaced that could mess up the sliding, maybe by limiting the travel if the calliper's offset in relation to the disc.

[Bibio]

if there were any spacers missing from the rear wheel assembly you would know about it.

the rear calliper only has 3 anti rattle/squeal shims. 2 are on the pads and the other is on the main carriage and the pads locate into it. now you could have disloged the carrier rattle shim as they are a PITA which might be causing the carrier to jam. other than that the rear brake on the pointy is a very simple affair and not much to go wrong.

can you post a few pics at different angles of the calliper on the bike?

[aesmith]

Not very easy to get any good angles, but for what it's worth. (By the way, most of the rust-brown is dust from the farm track)

http://i42.photobucket.com/albums/e320/GandyGoose/Tech/DSC_0538-CROP-1280_zps360cd760.jpg

And

http://i42.photobucket.com/albums/e320/GandyGoose/Tech/DSC_0537-CROP-1280_zps4dac5cca.jpg

[Bibio]

all looks fine to me. those pads are very thick.

your chain adjuster ends are the wrong way round though.

[aesmith]

Cheers. New pads just fitted, and there's only just enough room with the piston fully retracted. Can't remember the brand of these pads, they were the cheapest I could find just in case it rips through these in the same short time.

Will have to see what I find with a proper dismantle, I have a spare rebuilt calliper as well so could swap that over to rule out sticky piston. Also wondering if it could be wear in the sliding parts, so they move freely by hand but go slightly squint and bind in actual use.