Bottom Bracket Problem

Discussion in 'Cycling Equipment' started by George L. Porte, Sep 12, 2003.

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  1. I recently decided to play around with my old Bridgestone MB-6 and put together a cheap singlespeed
    with some parts that I have in the mostly used box. I wanted to change out the 10 yr old bottom
    bracket and make sure it was the right one for the crank I was going to use. I got the old one out
    but it wasn't easy. The cheap plastic cap was all broken up but it came out.

    I looked at the thread and on the drive side there was one spot that didn't look perfect but overall
    it looked OK. I wanted to make sure so I measured how far in the questionable spot was and it was
    about 13mm. The old bottom bracket that I had only had about 10mm of thread so I figured it would be
    OK. I took it by the shop to see what they thought and they screwed one in and said it should be OK.
    I asked how much to chase the threads and they said $30. They said that it wouldn't really be worth
    it with this old MB-6. I got a new BB of the correct size and went on home.

    I got home and put the cartridge in the drive side and then tried to put the cap in. I wouldn't go.
    I took the cartridge out and screwed the cap in OK. I then took the old crappy BB which screws into
    the non drive side and it went in OK too. I can't get both sides in together but separately is OK. I
    notice that when I thread the old one in the non-drive side the BB cartridge is concentric with the
    shell. When I thread the new one in the drive side, it is not concentric and is almost touching the
    bottom of the shell. I also took out the bottom cable guide screw thinking that might be the problem
    but it seems like the the shell is either not threaded right or bent. There doesn't appear to be any
    damage to the shell. I suppose the old BB which threaded into the non-drive (straight) side was less
    susceptable to the maladjusted (malthreaded) drive side because the cap is shorter and the
    misalignment is less noticeable with a shorter part.

    Is there a fix for this and is it worth fixing? The bike is a Bridgestone MB-6 (Tange frame).

    Thanks GP
     
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  2. In article <[email protected]>, George L. Porter, IV <gporter1970<nospam> wrote:
    >
    >I got home and put the cartridge in the drive side and then tried to put the cap in. I wouldn't go.
    >I took the cartridge out and screwed the cap in OK. I then took the old crappy BB which screws into
    >the non drive side and it went in OK too. I can't get both sides in together but separately is OK.

    Assuming there is nothing wrong with the replacement bottom bracket, you should be able to fix it
    with piloted BB taps. Good BB taps are designed to force both sides to remain on the same axis. $30
    sounds OK to me, if the bike suits you it's worth fixing at that price.

    --Paul
     
  3. On Fri, 12 Sep 2003 20:23:42 +0000, George L. Porter, IV wrote:

    > I got home and put the cartridge in the drive side and then tried to put the cap in. I wouldn't
    > go. I took the cartridge out and screwed the cap in OK. I then took the old crappy BB which
    > screws into the non drive side and it went in OK too. I can't get both sides in together but
    > separately is OK.

    Try threading the cartridge on partially, then starting the cap. Tighten them in together. Should
    work. With a cartridge, you do not need perfect alignment, you just need it to be held steady.

    --

    David L. Johnson

    __o | Do not worry about your difficulties in mathematics, I can _`\(,_ | assure you that mine
    are all greater. -- A. Einstein (_)/ (_) |
     
  4. I tried this too. The engagement splines are a little damaged on the plastic cup now so I really
    don't want to be forcing anything. I don't really want to throw any money at this project so tapping
    and facing may be out. It is off by quite a bit so if it is tapped, it might not be so secure
    because of a lack of bite on the threads.

    Maybe I can get a cheap cro-mo frame from someone else. I already spent $30 at the lbs for the UN-52
    which has a semi buggered plastic cup now.

    GP "David L. Johnson" <[email protected]> wrote in message
    news:[email protected]...
    > On Fri, 12 Sep 2003 20:23:42 +0000, George L. Porter, IV wrote:
    >
    > > I got home and put the cartridge in the drive side and then tried to put the cap in. I wouldn't
    > > go. I took the cartridge out and screwed the
    cap
    > > in OK. I then took the old crappy BB which screws into the non drive
    side
    > > and it went in OK too. I can't get both sides in together but
    separately
    > > is OK.
    >
    > Try threading the cartridge on partially, then starting the cap. Tighten them in together. Should
    > work. With a cartridge, you do not need perfect alignment, you just need it to be held steady.
    >
    > --
    >
    > David L. Johnson
    >
    > __o | Do not worry about your difficulties in mathematics, I can _`\(,_ | assure you that mine
    > are all greater. -- A. Einstein (_)/ (_) |
     
  5. On my bike the (second hand) UN - 52 bb arrived with no plastic cup so I just screwed it in and used
    a Cro mo cup from a Stronglight bb on the other side to hold it in place. It seemed as though the
    curved part for the balls centred and aligned the bb before locking it in place. Sounds daft but
    it's been working for over 400 miles now, not much of that on road either. I did eventually get hold
    of the proper part but couldn't get it to fit! Cheers Colin

    "George L. Porter, IV @cox.net>" <gporter1970<nospam> wrote in message
    news:[email protected]...
    > I tried this too. The engagement splines are a little damaged on the plastic cup now so I really
    > don't want to be forcing anything. I don't really want to throw any money at this project so
    > tapping and facing may
    be
    > out. It is off by quite a bit so if it is tapped, it might not be so
    secure
    > because of a lack of bite on the threads.
    >
    > Maybe I can get a cheap cro-mo frame from someone else. I already spent
    $30
    > at the lbs for the UN-52 which has a semi buggered plastic cup now.
    >
    > GP "David L. Johnson" <[email protected]> wrote in message
    > news:[email protected]...
    > > On Fri, 12 Sep 2003 20:23:42 +0000, George L. Porter, IV wrote:
    > >
    > > > I got home and put the cartridge in the drive side and then tried to
    put
    > > > the cap in. I wouldn't go. I took the cartridge out and screwed the
    > cap
    > > > in OK. I then took the old crappy BB which screws into the non drive
    > side
    > > > and it went in OK too. I can't get both sides in together but
    > separately
    > > > is OK.
    > >
    > > Try threading the cartridge on partially, then starting the cap.
    Tighten
    > > them in together. Should work. With a cartridge, you do not need
    perfect
    > > alignment, you just need it to be held steady.
    > >
    > > --
    > >
    > > David L. Johnson
    > >
    > > __o | Do not worry about your difficulties in mathematics, I can _`\(,_ | assure you that
    > > mine are all greater. -- A. Einstein (_)/ (_) |
    > >
    >
     
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