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Disc brake issues

ianpoolemanianpooleman Posts: 28
edited June 2010 in MTB workshop & tech
I am having some trouble with my front brake (avid juicy 3 on specialized rockhopper).

They seem to work fine initially but on lengthy descents they become worse and worse to the point where the lever hits the bar.

I have tried bleeding them and it helped slightly. I did however see that the fluid was full of what looked like brake dust (fine silver / black particles in the fluid).

It is a case of needing to change the fluid completely ? is it worth taking the calliper to bits and replacing the seals ?

Any help would be gratefully received

Posts

  • nicklousenicklouse Posts: 50,675 Lives Here
    sounds like you need to correctly bleed the system.

    or you have a leak.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Thanks for the useful suggestion, I used the same technique to bleed the rear and also both front and back on my partners bike too so I am fairly confident that the unit was adequately bled.

    Are there any parts of the system that are common for leaks to occur and are they repairable or easier to buy a replacement brake.
  • diydiy Posts: 6,473
    the particles from the bleed is normal, but its possible that you have a leak as suggested. You could pressure up the system (pump and then clamp the lever closed) over night and look for signs of leaks in the morning.
  • benpinnickbenpinnick Posts: 4,148
    My mates Avids did the same until we fully bled and refilled them, I think Avid might have some issues on QC for these when filling them.
    A Flock of Birds
    + some other bikes.
  • joshtpjoshtp Posts: 3,966
    you do realise Avid have a special bleed system using a £40 kit, dont you?!

    without the kit, it cant be done.
    I like bikes and stuff
  • nicklousenicklouse Posts: 50,675 Lives Here
    Thanks for the useful suggestion, I used the same technique to bleed the rear and also both front and back on my partners bike too so I am fairly confident that the unit was adequately bled.

    Are there any parts of the system that are common for leaks to occur and are they repairable or easier to buy a replacement brake.

    if you have bleed it correctly then strip it and see what is wrong, but what you are saying does sound like a poor bleed.

    if something had failed you would have fluid all over the place or a non working lever.

    so presuming that the lever feel is constant. then it could be contamination of the pads, but no you say the lever moves to the bar.

    re changing the fluid that would have happened when you bled the brakes as there is so little in the system just pushing a syringe half-full of fluid would have swapped all the fluid.

    so back to the poor bleed.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • ride_wheneverride_whenever Posts: 13,279
    you do realise Avid have a special bleed system using a £40 kit, dont you?!

    without the kit, it cant be done.

    ^^nonsense...

    It is however much easier with the kit.
  • Chunkers1980Chunkers1980 Posts: 8,035
    Yeah - I've seen someone with a home made kit that cost about a pound.
  • joshtpjoshtp Posts: 3,966
    you do realise Avid have a special bleed system using a £40 kit, dont you?!

    without the kit, it cant be done.

    ^^nonsense...

    It is however much easier with the kit.

    ok, so you CAN do it without the kit, and you can do it with a homemade kit, but IME its not very effective, iv done both, and both failed to make much difernce... the kit does make it alot easyer.
    I like bikes and stuff
  • ride_wheneverride_whenever Posts: 13,279
    worked fine on my housemates rear brake, even though the caliper is split...
  • joshtpjoshtp Posts: 3,966
    worked fine on my housemates rear brake, even though the caliper is split...
    nice one... didnt work for me though, so must be a bit of a hit and miss thing, eithr that or youv got some sweet avid with out the kit bleed skilz...



    :wink:
    I like bikes and stuff
  • ride_wheneverride_whenever Posts: 13,279
    it did take two of us, although i'm fairly convince that's because the brake was off the bike...
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