Front disc brake issues

starbuck
starbuck Posts: 256
edited December 2014 in MTB workshop & tech
I have xt hydraulic brakes (785's). Recently, my front brake has been playing up. The braking on it is very poor and wet or dry, it squeals like anything whenever I use it (pad's aren't rubbing).

I thought it may be pad contamination so I changed the pads and now have sintered pads. I also cleaned up the rotor at the same time with muc off disc brake cleaner.

My front brake seemed fine for a week or so, but the same thing has now happened - the brakes squeal like anything and I'm mainly using the back brake when on road. I've also bled the brake to ensure it wasn't air in the system.

Any ideas? I love these brakes and when they're working the braking is awesome, but I lose confidence when riding when I don't have fully working brakes, so am less inclined to go riding.

Comments

  • miceden
    miceden Posts: 225
    Squealing is more often than not down to contamination - are you using a different cleaner on your bike, spraying anything on it post ride/cleaning or is it stored near anywhere where something is sprayed, are Pistons ok and all the hoses done up correctly i.e. oil isn't leaking out and somehow getting onto the pads? You could be picking up contaminates where you are riding... Oil on the road, in standing water on farm tracks, etc

    Otherwise have you checked that everything is aligned and bolts done up correctly, nothing loose or rubbing, if you spin the wheel does the disc rub at any point on the pads?

    Any abnormal wear on the pads or disc? How old are the discs?
  • Ouija
    Ouija Posts: 1,386
    Incidental side note:

    When wiping down rotors don't use tissue paper or toilet paper or any kind of "soft on the skin" types of materials.

    Why? Because tissue paper is quite course and scratchy in it's natural form, so they soften it by lightly moisturizing it. Not with water (which would evaporate), but with OILS. Typically Aloe Vera and other oils taken from plant extracts. Which you then proceed to wipe all over your rotors while thinking your wiping gunk off them, instead of putting gunk on them.

    Use the driest, scratchiest, coarsest kitchen towel instead (typically the cheapest). These typically don't have any oils embedded in them.
  • Antm81
    Antm81 Posts: 1,406
    Ouija wrote:
    Incidental side note:

    When wiping down rotors don't use tissue paper or toilet paper or any kind of "soft on the skin" types of materials.

    Why? Because tissue paper is quite course and scratchy in it's natural form, so they soften it by lightly moisturizing it. Not with water (which would evaporate), but with OILS. Typically Aloe Vera and other oils taken from plant extracts. Which you then proceed to wipe all over your rotors while thinking your wiping gunk off them, instead of putting gunk on them.

    Use the driest, scratchiest, coarsest kitchen towel instead (typically the cheapest). These typically don't have any oils embedded in them.

    Or any toilet paper provided by a publicly funded organisation, it is the driest, roughest stuff known to man.
    Trance 27.5 Hoodoo Her Scott Contessa Daughter's Vulcan
  • Paul Stumpy FSR
    Paul Stumpy FSR Posts: 59
    mine are doing exactly the same and are also M785's. Really frustrating isnt it. I've also throughly cleaned and changed to metal pads.
    Have a look in my thread for other advice
    viewtopic.php?f=10004&t=13006783
    Its in the lbs at the moment, so hopefully they will find something wrong.
    good luck
  • swod1
    swod1 Posts: 1,639
    I've also tried the muc off bike disc brake cleaner and found it was ok but not as good as some ipa alcohol and blue paper towel.

    Its a strange one this as I only have noise coming from the brakes on my bike when the pads get wet and then it goes away after using the brakes which are also m785 xt's. I'm not sure what type of pads are in there as I've not touched the brakes since fitting them, made the mistake before of fiddling about and then making things worse.

    only thing I've been doing is cleaning the discs every now and then with some ipa and when cleaning the rear cassette putting a plastic food bag over the disc to avoid anything getting on it, degreaser, oil etc.

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