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Squeeky rear disc brake

Pork SwordPork Sword Posts: 268
edited February 2011 in MTB workshop & tech
I need a bit of advice... I have some new Shimano SLX disc brakes on my Scott Scale. Being new to hydraulic brakes I'm not exactly an expert on how to get them working sweetly. They stop great, it's just that the rear brake has a tendency to drag ever-so-slightly leading to a irritating pinging noise which disappears when I put some brake pressure on (not enough to brake, but enough to stop the squeeking noise). What I want to know is: would bleeding the brake help or has anyone else experienced a similar problem but used a different method to provide a cure? Any ideas?
let all your saddles be comfy and all your rides less bumpy....

Posts

  • cooldadcooldad Posts: 32,904
    Have you centred the calliper?
    Bleeding won't help - that's for spongy brakes.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Yep. I've centred the caliper by messing around with the shims but to no avail. I can move the position of the caliper in the direction you think would help (look at the brake pad that's closest to the rotor and create more space by adding an extra shim etc) but it just seems to make the problem worse - no matter how much re-shimming I do.... Was wondering if I could play around with the brake pads to see if that could help?
    let all your saddles be comfy and all your rides less bumpy....
  • cooldadcooldad Posts: 32,904
    Loosen the bolts holding the calliper on, squeeze the brake to centre the calliper, tighten the bolts, release the brake.
    No need to play with shims.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Thanks for the response. I'll give that a go. Hydraulics... great stopping power but not the easiest to make adjustments to.
    let all your saddles be comfy and all your rides less bumpy....
  • cavegiantcavegiant Posts: 1,546
    Some people will disagree with this advice but it works great for me.

    Most pads do not fire equally, so having something centred perfectly will mean the pads hit unevenly.

    Try lining up the pads to when they hit the rotor the rotor does not move AT ALL.
    when centred there is normally a bit of deflection, aim to remove this.

    It might not be the purest method of fixing (as you should really be rebuilding your brakes to make sure the pads more equally) but it is a lot less effort and seems to work perfectly.
    Why would I care about 150g of bike weight, I just ate 400g of cookies while reading this?
  • cooldadcooldad Posts: 32,904
    The normal method I described does actually centre the pads, not the calliper if you think about it..
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • bluechair84bluechair84 Posts: 4,352
    try resetting the pistons, wedge a flat screwdriver between the pads and twist - don't lever. You'll work the pads back to their most open.
    I've got SLXs and haven't had a problem with squeal, you could try cleaning the pads and rotor as well though you should do it with a proper brake cleaner.
  • cavegiantcavegiant Posts: 1,546
    cooldad wrote:
    The normal method I described does actually centre the pads, not the calliper if you think about it..

    Very true, I was just going in to a bit more detail. As the disk moves a bit with your method (especially on larger disks), it needs a bit of manual assistance to line up perfectly.
    Why would I care about 150g of bike weight, I just ate 400g of cookies while reading this?
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