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So I have two bikes and a year ago I went through the challenge of unscrewing a stuck BB. The solution was to put the tool in a vice and twist the frame around it.

Today I have an even more difficult challenge. My cheaper bike is now about 5 years old and has been through dust, mud and salty snow. The BB is rattling and needs to be changed. I tried.

The BB is obviously cheap, both cups being plastic. I used the proper tool, put an elongation bar on the wrench, followed the correct direction for unscrewing ... and ruined both of my cups. The wrench just cut through the plastic teeth of the cup.

My BB is of the following type:

enter image description here

What can I do? I tried drying the cups apart with a soldering iron - which cut through the plastic somehow. Can I inject something inside, that will melt the cups? Can I pour spirits and set it alight, without damaging my aluminum frame and the paint around?

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  • The BB looks like you could "attack" the notches in the outer, metallic ring with the correct tool. This way, you could at least get one side out.
    – arne
    Commented Aug 19, 2013 at 9:12
  • @arne, Both cups and the drive-side ring are plastic and smooth. On the picture is not my exact BB.
    – Vorac
    Commented Aug 19, 2013 at 9:20
  • Oh, OK. Then at least I don't see a good possibility without damaging the paint job. If you loosen that requirement, you could try blowtorching the cups away...
    – arne
    Commented Aug 19, 2013 at 9:21
  • @arne, in the end SOMETHING has to be done, I do not want to ditch the frame. The only hard requirement is that the bike is usable i.e. the thread is not damaged. Just ... I do not have easy access to a blowtorch.
    – Vorac
    Commented Aug 19, 2013 at 9:23
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    The standard plumber's solution is to somehow just cut out the cup. Exactly how you'd do this is hard to say -- I'd probably have a shot at drilling through it in several places with a small drill bit. You would, of course, need to avoid gouging the soft aluminum threads too badly, but a few nicks wouldn't hurt so long as you "chased" them afterwards with, eg, an old steel cup.
    – Daniel R Hicks
    Commented Aug 19, 2013 at 11:08

1 Answer 1

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I thought about this a little more, and here is what I'd probably attempt:

The cup has a "shoulder" on the inside that retains the bearing cartridge. Attack the shoulder somehow (break it, use your Dremel, et al) until it's possible to drive out the cartridge from the other end. Then, with the cartridge out, is should be possible to pry the remainder of the cup out with minimal damage to the threads.

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  • I'd cut it with a Stanley knife rather than use a Dremel. Slow, but less risk of damaging the threads.
    – armb
    Commented Sep 26, 2013 at 10:10

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