Please help me stop my brakes squealing

Notable hobbit
Notable hobbit Posts: 28
edited February 2017 in MTB workshop & tech
I got a second hand bike with hydraulic disc brakes and when I bought it the brakes squealed. At the time I thought this was because they where dirty/oily but since getting it home I have cleaned the rotors thoroughly with meths and I have sanded the top layer off the pads, I have also bedded in the pads (~25 stops at reasonable speed) but my breaks still squeal. Does anyone know how to fix this?

Comments

  • JBA
    JBA Posts: 2,852
    Align the callipers properly.
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  • Notable hobbit
    Notable hobbit Posts: 28
    Just realigned the callipers but they are still squealing. Thanks for the suggestion though, I hadn't thought of that.
  • swod1
    swod1 Posts: 1,639
    Notable hobbit wrote:
    Just realigned the callipers but they are still squealing. Thanks for the suggestion though, I hadn't thought of that.

    After all that I would fit some new pads that should cure it.

    What brakes are they?
  • Notable hobbit
    Notable hobbit Posts: 28
    They are Shimano Alivio
  • swod1
    swod1 Posts: 1,639
    Notable hobbit wrote:
    They are Shimano Alivio

    Shimano shouldn't squeal if setup correctly. I had these brakes and didn't have this problem.

    I think the pads are done if you've filled off the top layer and still making noise.

    Did you give the disc a good clean with isopropyl alcohol?

    Maybe the discs are warped too causing the noise.
  • poah
    poah Posts: 3,369
    sand the discs
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  • cooldad
    cooldad Posts: 32,599
    Fact - 99.9985466433% of all brake problems are caused by people doing random things to their brakes.

    Don't sand anything. Don't mess with them.

    Make sure the rotors are clean, buy new pads if the old ones are contaminated. Make sure the caliper is aligned and centred.

    Bed the pads in.

    Then just leave them alone.

    Brakes squeal sometimes. If they work live with it.
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  • cooldad
    cooldad Posts: 32,599
    ps. Don't clean with meths. It can leave a residue. It is ethanol mixed with some methanol to make it poisonous, a bitter substance to make it undrinkable, and a purple dye to warn you what it is.
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  • poah
    poah Posts: 3,369
    cooldad wrote:
    Don't sand anything. Don't mess with them.

    odd that it stopped the squealing on many brakes I've done It to.
    CCDB IL coil CS first impressions

    MTB Scotland youtube channel
  • cooldad
    cooldad Posts: 32,599
    Possibly if the pads were glazed. Which doesn't happen if they are bedded in. And not dragged all the way doen the hill.
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