Rear brake lack of power

echowitch
echowitch Posts: 196
edited January 2019 in MTB workshop & tech
My rear brake is lacking power. I would say it has 50% to 75% of the front break. It gives both far less power and when I have applied full rear brake it squeals like a pig trying to escape a pervert ;)

Before taking it to my local shop and potentially racking up a big bill and losing the bike for several days I am trying to determine if it is something I can fix. I am wondering if:

1. The brake pads are worn or contaminated
2. The brake disk is worn and needs replacing
3. The brakes need bleeding.

The brakes are: Shimano BR-M445 hydr. discbrake

viewtopic.php?f=10017&t=12909607&p=18232871

Comments

  • JBA
    JBA Posts: 2,852
    If you haven't changed the pads since 2013 then I'd suggest the first thing you do is check them. It only takes 2 minutes and may solve your problem. The squealing could be the metal backing plate rubbing on the disc.

    This seems to be a recurring problem for you:

    viewtopic.php?f=10004&t=12922532&p=18324278#p18324278

    viewtopic.php?f=10004&t=12940397&p=18524165#p18524165

    Are you dragging your brakes a lot?
    “Life has been unfaithful
    And it all promised so so much”

    Giant Trance 2 27.5 2016 ¦ Sonder Broken Road 2021¦ Giant Revolt Advanced 2 2019 ¦ Giant Toughtroad SLR 1 2019 ¦ Giant Anthem 3 2015 ¦ Specialized Myka Comp FSR 2009
  • echowitch
    echowitch Posts: 196
    Brake pads were replaced last year, but the bike has been barely used since then. I don't think I getting brake drag but I will check. :)
  • cooldad
    cooldad Posts: 32,599
    Clean the rotors with IPA, replace the pads and see.
    I don't do smileys.

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  • billycool
    billycool Posts: 833
    It could be any of the 3 things that you mention. I've suffered from all of them at some point.

    It could also be that you have a sticky piston and maybe it's not getting a decent braking force?
    Your caliper might be slightly off-centre? (also check bolts are secure).

    Most recently when I had a similar issue, my rotors were worn and putting new rotors in transformed the brakes.

    I'd suggest check pads and rotors first. Check for leaks and contamination. Check for sticky pistons. Bleed.

    See what they are like after that.
    "Ride, crash, replace"
  • The Rookie
    The Rookie Posts: 27,812
    Could just be the pads have soaked up a load of humidity and need some decent action to warm up and dry out.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • echowitch
    echowitch Posts: 196
    Cheers all, I'll have a play with them (try swapping the pads) and see if that fixes it. If not......I guess it will be pass it to the experts time

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