Cantilever brake failure

Discussion in 'UK and Europe' started by fitzharrys, Oct 20, 2004.

  1. fitzharrys

    fitzharrys New Member

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    Recently the front brakes on my son's bike were repaired by a local cycle shop. Within 2 days, they failed - a brake block became jammed under the rim, throwing my son from the bike.

    I am wondering how this can happen with cantilever brakes, if they are properly set up.
     
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  2. Al C-F

    Al C-F Guest

    On Wed, 20 Oct 2004 21:23:24 +1000, fitzharrys
    <[email protected]> wrote:

    >
    >Recently the front brakes on my son's bike were repaired by a local
    >cycle shop. Within 2 days, they failed - a brake block became jammed
    >under the rim, throwing my son from the bike.
    >
    >I am wondering how this can happen with cantilever brakes, if they are
    >properly set up.


    My guess would be that the brake block was mounted too high in the
    cantilever and therefore had to point downwards to line up with the
    rim. After a bit of use, the block would squirm even further
    downwards until it slipped under the rim.

    When you install the blocks, look at where the pivot is - the boss on
    the fork - and think what the direction of the force will be. You
    want the block mounting to be at right angles (more or less) to the
    cantilever arm.
     
  3. m-gineering

    m-gineering Guest

    fitzharrys wrote:
    >
    > Recently the front brakes on my son's bike were repaired by a local
    > cycle shop. Within 2 days, they failed - a brake block became jammed
    > under the rim, throwing my son from the bike.
    >
    > I am wondering how this can happen with cantilever brakes, if they are
    > properly set up.


    poor setup, insufficient tightening, setup with frontwheel skewed,
    riding with frontwheel skewed, levering wheel in/out fork without
    releasing brake, excessive brakeblock wear (but in two days you'll need
    a lot of mud to accomplish that)
    --
    ---
    Marten Gerritsen

    INFOapestaartjeM-GINEERINGpuntNL
    www.m-gineering.nl
     
  4. jtaylor

    jtaylor Guest

    fitzharrys <[email protected]> wrote in
    message news:[email protected]
    >
    > Recently the front brakes on my son's bike were repaired by a local
    > cycle shop. Within 2 days, they failed - a brake block became jammed
    > under the rim, throwing my son from the bike.
    >
    > I am wondering how this can happen with cantilever brakes, if they are
    > properly set up.


    It can't, but setting them up and adjusting them as they wear is important.

    Go back to that cycle shop ONCE. Tell them what happened, and that you will
    not return. Despite the poor wages the cycle trade provides, setting a
    brake block correctly is not difficult, and you have grounds for avoiding
    them.
     
  5. Dave Kahn

    Dave Kahn Guest

    fitzharrys <[email protected]> wrote in message news:<[email protected]>...
    > Recently the front brakes on my son's bike were repaired by a local
    > cycle shop. Within 2 days, they failed - a brake block became jammed
    > under the rim, throwing my son from the bike.
    >
    > I am wondering how this can happen with cantilever brakes, if they are
    > properly set up.


    It's a known, and extremely dangerous, failure mode of badly adjusted
    cantis. The usual reason is failing to realign them as the brake
    blocks wear. Had they worn that much in only 2 days? The most probable
    explanations would seem to be that either the shop adjusted them
    badly, (or they failed to tighten them properly which is much the same
    thing really), or something happened to them after the bike left the
    shop. This could be someone fiddling with them, or it could be a fall,
    for example.

    --
    Dave...
     
  6. fitzharrys

    fitzharrys New Member

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    No, the bike had hardly been used.
     
  7. fitzharrys

    fitzharrys New Member

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    I did go back to the shop (Rides on Air in Abingdon) but no joy. A bit worrying really.

    Oh well, I guess there are other cycle shops in town.
     
  8. jtaylor

    jtaylor Guest

    fitzharrys <[email protected]s.com> wrote in
    message news:[email protected]
    >
    > jtaylor Wrote:
    > >
    > > Go back to that cycle shop ONCE. Tell them what happened, and that
    > > you will
    > > not return. Despite the poor wages the cycle trade provides, setting
    > > a
    > > brake block correctly is not difficult, and you have grounds for
    > > avoiding
    > > them.

    > I did go back to the shop (Rides on Air in Abingdon) but no joy. A bit
    > worrying really.
    >
    > Oh well, I guess there are other cycle shops in town.
    >


    Braggs, as I remember. Much better.
     
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