Hub brake snatches

Discussion in 'Cycling Equipment' started by Daniel Towner, Apr 22, 2004.

  1. Hi all,

    I have hub-brakes on my two front wheels (Windcheetah!) and one of
    them has developed an annoying habit of snatching. If I brake fairly
    gently, both wheels will slow down equally and I'll come to a smooth
    stop. If I brake harder, one wheel will lock up completely, which then
    tries to spin the trike. This behaviour is worse in damp weather. If I
    loosen the faulty brake I can stop it from snatching, but then its so
    loose that under gentle braking it does nothing. I can't see any
    obvious damage to the braking surface inside the hub, but the edges of
    the brake shoes look ragged - not squared off as on the good brake.

    Any ideas how I can cure this?

    thanks,

    dan.
     
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  2. m-gineering

    m-gineering Guest

    Daniel Towner wrote:

    > Hi all,
    >
    > I have hub-brakes on my two front wheels (Windcheetah!) and one of
    > them has developed an annoying habit of snatching. If I brake fairly
    > gently, both wheels will slow down equally and I'll come to a smooth
    > stop. If I brake harder, one wheel will lock up completely, which then
    > tries to spin the trike. This behaviour is worse in damp weather. If I
    > loosen the faulty brake I can stop it from snatching, but then its so
    > loose that under gentle braking it does nothing. I can't see any
    > obvious damage to the braking surface inside the hub, but the edges of
    > the brake shoes look ragged - not squared off as on the good brake.
    >
    > Any ideas how I can cure this?
    >
    > thanks,
    >
    > dan.

    if the brakearm returns normally it could be caused by wear changing the
    geometry of the brake. Drumbrakes are fairly sensitive to changes in
    geometry causing it to self-energize. New and thicker shoes should cure it.
    /MArten
     
  3. Daniel Towner wrote:

    > I have hub-brakes on my two front wheels (Windcheetah!) and one of
    > them has developed an annoying habit of snatching. If I brake fairly
    > gently, both wheels will slow down equally and I'll come to a smooth
    > stop. If I brake harder, one wheel will lock up completely, which then
    > tries to spin the trike. This behaviour is worse in damp weather. If I
    > loosen the faulty brake I can stop it from snatching, but then its so
    > loose that under gentle braking it does nothing. I can't see any
    > obvious damage to the braking surface inside the hub, but the edges of
    > the brake shoes look ragged - not squared off as on the good brake.
    >
    > Any ideas how I can cure this?


    I don't know the details of the cable routing on the Windcheetah, but
    this sounds as if the brake mechanism plate is not properly secured, and
    is being rotated in such a way as to increase pull on the cable.

    I would suggest careful examination of this, but without seeing it I
    can't get more specific.

    There are right-hand and left-hand drum brake units available, and you
    should have a mirror image pair on your trike...do you?

    Sheldon "Symmetry" Brown
    +-------------------------------------------+
    | Good judgment comes from experience, |
    | and experience comes from bad judgment. |
    | --Fred Brook |
    +-------------------------------------------+
    Harris Cyclery, West Newton, Massachusetts
    Phone 617-244-9772 FAX 617-244-1041
    http://harriscyclery.com
    Hard-to-find parts shipped Worldwide
    http://captainbike.com http://sheldonbrown.com
     
  4. Jeff Wills

    Jeff Wills Guest

    [email protected] (Daniel Towner) wrote in message news:<[email protected]>...
    > Hi all,
    >
    > I have hub-brakes on my two front wheels (Windcheetah!) and one of
    > them has developed an annoying habit of snatching. If I brake fairly
    > gently, both wheels will slow down equally and I'll come to a smooth
    > stop. If I brake harder, one wheel will lock up completely, which then
    > tries to spin the trike. This behaviour is worse in damp weather. If I
    > loosen the faulty brake I can stop it from snatching, but then its so
    > loose that under gentle braking it does nothing. I can't see any
    > obvious damage to the braking surface inside the hub, but the edges of
    > the brake shoes look ragged - not squared off as on the good brake.
    >
    > Any ideas how I can cure this?
    >
    > thanks,


    Hmmm... sounds like a question for Bob Dixon, but I'd start by
    thoroughly cleaning the inside the drum with an evaporating solvent
    (alcohol or acetone) and dressing the brake shoes with light
    sandpaper.

    jeff
     
  5. Werehatrack

    Werehatrack Guest

    On 22 Apr 2004 02:49:19 -0700, [email protected] (Daniel Towner)
    may have said:

    >Any ideas how I can cure this?


    In powered vehicle applications, this is usually a sign of
    contamination of the friction material. Unfortunately, it is usually
    futile to try to remove the contamination. I'd replace the brake
    shoes and throughly clean the inside surface of the drums.

    If you want to try something short of that, use emery cloth to deglaze
    the inside of the drum, use sandpaper to scuff the surface of the
    shoes, and try to clean the friction material's surface with a
    degreaser that will not leave a residue. In my opinion, it probably
    won't work, but you might get lucky.

    --
    My email address is antispammed; pull WEEDS if replying via e-mail.
    Typoes are not a bug, they're a feature.
    Words processed in a facility that contains nuts.
     
  6. > I have hub-brakes on my two front wheels (Windcheetah!) and one of
    > them has developed an annoying habit of snatching. If I brake fairly
    > gently, both wheels will slow down equally and I'll come to a smooth
    > stop. If I brake harder, one wheel will lock up completely, which then
    > tries to spin the trike. This behaviour is worse in damp weather. If I
    > loosen the faulty brake I can stop it from snatching, but then its so
    > loose that under gentle braking it does nothing. I can't see any
    > obvious damage to the braking surface inside the hub, but the edges of
    > the brake shoes look ragged - not squared off as on the good brake.


    In the end I used emery paper to aggressively rub down the braking
    surfaces, and then cleaned the inside of the hubs with acetone. The
    brakes no longer snatch, and they perform better than they have done
    in ages.

    Thanks for you help.

    dan.
     
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