Mtb brakes

Adam.carr3
Adam.carr3 Posts: 3
edited November 2019 in MTB workshop & tech
Hi
Just wondering if anyone has any suggestions. My shimano hydraulic disc breaks squeal and have lower break power when dry. If I wet them they are great, powerful and quiet. I’ve bled them as routine maintenance and rubbed the pads down as well as giving it a good all round clean of the Caliper and rotors.

Cheers

Comments

  • figbat
    figbat Posts: 680
    Brakes - it’s “brakes”.

    Have you cleaned the rotors? Some brake cleaner or isopropyl alcohol will shift any oily residue on the surface.
    Cube Reaction GTC Pro 29 for the lumpy stuff
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  • The Rookie
    The Rookie Posts: 27,812
    What did you clean it with?
    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.
  • Adam.carr3
    Adam.carr3 Posts: 3
    Thanks for the replies, and sorry about the ‘autocorrect’ I cleaned it all down with muc off disc brake cleaner. Instantly noisy and low power when reassembled. As soon as I poured a little water on front and back disc/pads etc noise gone and power back. Then this morning dried out and noise back? Cheers
  • JBA
    JBA Posts: 2,852
    Make sure the calipers are aligned properly.
    It may be worth ditching your brake pads in case they are contaminated and fitting new ones, but make sure you clean the rotors again before using them.
    Also bed the new pads in properly.
    “Life has been unfaithful
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  • Adam.carr3
    Adam.carr3 Posts: 3
    No worries I’ll give it a go but just wanted to check I hadn’t missed something as it seemed strange to me - I wouldn’t expect a few drops of water to improve things so much if rotors/pads contaminated. Thanks for your replies everyone
  • steve_sordy
    steve_sordy Posts: 2,443
    Try the disco inferno on your pads.

    Lay the pads on a concrete surface, braking surface upwards. One at a time pour some disc brake cleaner or iso-propyl alcohol onto the pad. Then set fire to it with a blowlamp and keep the blowlamp on it until the black smoke stops and the corners of the pad material are glowing red. Do the other pad while the first one cools. The black smoke is any contaminant burning off.

    Once the pads are cool again, place some 100 grit sandpaper or emery cloth onto a smooth flat surface and rub the pad surface over the material in a circular motion for 5 seconds or so. That is just to break up the surface. Then refit the pads and go bed them in from scratch.

    If that doesn't work, your pads are too badly contaminated; go get some new ones.

    If that doesn't work, then I believe that you have some very fine bubbles in your hydraulic line and it is worth getting them properly bled.

    The other suggestions about alignment etc are all valid and I'm assuming that you have sorted all that out.

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