Rear brake massive squeal and loss of power

nickfrog

Hiya,

This just suddenly "happened". I loosened the caliper to try an re-align it but I can't prevent it from "bending" the disc slightly on one side prior to the other pad entering in contact with the disc, is that the cause of the issue ? Bent or misaligned disc ? Would that also cause the massive loss of power too ?

Cheers

Confused of Sussex.

nicklouse

contaminated pads.

sounds like you may have undone the wrong bolts.

what brakes? which bolts?

tofu21

Sounds like you've got a stuck piston.

Try holding the one that moves open and pump the brakes to get the stuck one moving.

nickfrog

Sorry. SLX 160mm with centre lock. Frame is older so there is a an adapter attached to the frame. I did not undo the bolts that attache the adapter to the frames but the ones that attach the caliper to the adapter, which gave me lateral movement. I just retried and however accurate I tried to be, when I tighten the bolts and then release the brake lever, it still does not seem to bind the disc properly, as in one one of the pads is almost already touching the disc and therefore bends the disc prior to the other pad pressing against the disc. Will try do free up potentially stuck piston.

Maybe, as Nick said, the pads are contaminated and it will go back to normal with new pads...

nicklouse

often you have to hold the caliper to stop some movement when tightening.

little by little end by end till it behaves then tight then bed in.

The Rookie

Maybe its been run out of line and now the pad is worn at an angle and won't sit straight?

Pad down to metal backplate?

Simon

nickfrog

nicklouse wrote:

often you have to hold the caliper to stop some movement when tightening.

little by little end by end till it behaves then tight then bed in.

Cheers Nick, will try again !

There is still about 50% of the pad material left.

5pudgun

Undo the bolts again,apply the brake and tighten up with the brake on.Should be centred when released.

nickfrog

Cheers. The normal procedure does not work in my case as Nick suggested. I managed to get a perfect alignment by trial and error and the disc is now perfectly centred.... which has not solved the problem.

Ordered some sintered pads from Superstar.

How do I change them BTW ? Is it just a case of removing the pin with plyers and inserting the new pads ?

5pudgun

nickfrog wrote:

How do I change them BTW ? Is it just a case of removing the pin with plyers and inserting the new pads ?

pretty much yes, may be a guide on you tube,have a look

nickfrog

5pudgun wrote:

nickfrog wrote:

How do I change them BTW ? Is it just a case of removing the pin with plyers and inserting the new pads ?

pretty much yes, may be a guide on you tube,have a look

Cheers changed them today, how easy. These are the old pads:



Is that what contaminated pads would look like ?

There is much less travel at the lever now and hardly any space between pad and disk so I assume there is no automatic compensation for pad wear as on a car ?

nicklouse

yes there is auto adjustment.

did you push the pistons full home, sounds like you did not.

nickfrog

No, I did not push no pistons no more (triple negative!!). TBF, I quite like a grabby, on/off lever like that, even at the obvious detriment of modulation. Is it OK to just leave it like that Nick (from a mechanical point of view) ? Cheers.