Bottom bracket fixed cup loosens-knackered frame?

Discussion in 'Cycling Equipment' started by Steve Pells, Jun 18, 2003.

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  1. Steve Pells

    Steve Pells Guest

    Hello-

    I've just had my frame resprayed. This necessitated removal of a fused-in fixed cup first. I've put
    the bike back together, and noticed today (380 miles since rebuild) that the fixed cup loosened up.
    It didn't seem possible to retighten the cup properly as the cup loosened again by a thread or two
    on reaching the edge of the shell suggesting that the threads inside the BB shell are damaged. I
    asked the bike shop to chase the threads to remove any paint after the respray.

    Is my bike dead? I hope not.

    Thanks for any help.

    Steve Pells Edinburgh, UK

    stevie at holyrood dot ed dot ac dot uk (Above email is a spam midden, sorry)
     
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  2. Jobst Brandt

    Jobst Brandt Guest

    Steve Pells writes:

    > I've just had my frame re-sprayed. This necessitated removal of a fused-in fixed cup first. I've
    > put the bike back together, and noticed today (380 miles since rebuild) that the fixed cup
    > loosened up. It didn't seem possible to re-tighten the cup properly as the cup loosened again by a
    > thread or two on reaching the edge of the shell suggesting that the threads inside the BB shell
    > are damaged. I asked the bike shop to chase the threads to remove any paint after the re-spray.

    You should have asked them to reinstall the fixed cup and let them decide whether running a tap into
    the threads was necessary, which it probably wasn't, unless the painter was a dunce. This would have
    saved some money and gotten the right hand cup installed properly. Right hand thread right side cups
    require high torque to be properly secured. Take your bicycle to the shop and have them tighten the
    cup. If the threads aren't stripped, they can get it tight.

    Jobst Brandt [email protected] Palo Alto CA
     
  3. While were on this subject, should the paint be removed from the faces of the bottom bracket shell
    to guarantee that the two sides are parallel to each other, or does it matter? I had one bike shop
    tell me it doesn't matter, while another tell me I should remove the paint. Said when I tighten down
    on the bottom bracket cups & locking ring, the paint could work the bottom bracket loose. Perhaps it
    depend how much paint is on the face of the shell? If the shell needs to be faced, what would you
    recommend for "home tool facing"? Would a flat honing stone and kerosene do the trick? -tom

    <[email protected]> wrote in message news:%g4Ia.3555$%[email protected]...
    > Steve Pells writes:
    >
    > > I've just had my frame re-sprayed. This necessitated removal of a fused-in fixed cup first. I've
    > > put the bike back together, and noticed today (380 miles since rebuild) that the fixed cup
    > > loosened up. It didn't seem possible to re-tighten the cup properly as the cup loosened again by
    > > a thread or two on reaching the edge of the shell suggesting that the threads inside the BB
    > > shell are damaged. I asked the bike shop to chase the threads to remove any paint after the
    > > re-spray.
    >
    > You should have asked them to reinstall the fixed cup and let them decide whether running a tap
    > into the threads was necessary, which it probably wasn't, unless the painter was a dunce. This
    > would have saved some money and gotten the right hand cup installed properly. Right hand thread
    > right side cups require high torque to be properly secured. Take your bicycle to the shop and have
    > them tighten the cup. If the threads aren't stripped, they can get it tight.
    >
    > Jobst Brandt [email protected] Palo Alto CA
     
  4. Jobst Brandt

    Jobst Brandt Guest

    Tom Nakashima writes:

    > While were on this subject, should the paint be removed from the faces of the bottom bracket shell
    > to guarantee that the two sides are parallel to each other, or does it matter? I had one bike shop
    > tell me it doesn't matter, while another tell me I should remove the paint.

    Good painters generally mask off the BB across both faces, but no, I don't believe it has any
    effect because tightening torque will take care of that by extruding any paint (aka lubricant) on
    that face.

    > Said when I tighten down on the bottom bracket cups & locking ring, the paint could work the
    > bottom bracket loose. Perhaps it depend how much paint is on the face of the shell? If the shell
    > needs to be faced, what would you recommend for "home tool facing"? Would a flat honing stone and
    > kerosene do the trick?

    I would just run a flat file across the face if I thought there was enough old paint to
    warrant that, but how did the paint get there? If I had a frame painted, I would hold the
    painter responsible to keep all those surfaces that should not be painted, free from paint. If
    it's a purchased bicycle that is being maintained, I doubt that there would be enough paint on
    those surfaces.

    I keep hearing so much about facing the BB shell to be parallel and clean of paint, it sounds like
    these pieces are hand made in some primitive land by people who have no idea how they are to be
    used. I have not seen such a BB in the years I have worked on bicycles.

    Jobst Brandt [email protected] Palo Alto CA
     
  5. A Muzi

    A Muzi Guest

    "Steve Pells" <[email protected]> wrote in message
    news:[email protected]...
    > Hello-
    >
    > I've just had my frame resprayed. This necessitated removal of a fused-in fixed cup first. I've
    > put the bike back together, and noticed today (380 miles since rebuild) that the fixed cup
    > loosened up. It didn't seem possible to retighten the cup properly as the cup loosened again by a
    > thread or two on reaching the edge of the shell suggesting that the threads inside the BB shell
    > are damaged. I asked the bike shop to chase the threads to remove any paint after the respray.
    >
    > Is my bike dead? I hope not.

    That's unfortunate because metalwork is best done just _before_ a respray.

    Have a direct and calm talk with the owner of the shop. Ask that you watch while your BB is removed.
    If indeed the shop botched the threads when chasing them you should expect them to make it right (
    either secure the cup or repair the frame).

    At any rate don't panic until you see if there is a problem and know the extent of it.

    --
    Andrew Muzi http://www.yellowjersey.org Open every day since 1 April 1971
     
  6. Steve Pells

    Steve Pells Guest

    [email protected] wrote in message news:<%g4Ia.3555$%[email protected]>...

    > Right hand thread right side cups require high torque to be properly secured. Take your bicycle to
    > the shop and have them tighten the cup. If the threads aren't stripped, they can get it tight.
    >

    It's actually a left-handed thread (British frame). I hope you're right; I'll take it in
    this evening.

    Thanks very much.

    Steve

    Steve Pells Edinburgh, UK

    stevie at holyrood dot ed dot ac dot uk (Above email is a spam midden, sorry)
     
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