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Bottom bracket non-drive side keeps loosening

the_hundredth_idiotthe_hundredth_idiot Posts: 813
edited February 2018 in The workshop
My 1990s GT Paloma “pub bike” has a problem.

I stripped it down a few months ago, greased everything, new bearings, new chain, new cables, etc. It all works great now except for the bottom bracket.

The non-drive cup (old school cup and cone rather than sealed unit) keeps coming loose. It comes loose almost immediately. The lock ring is still tight (takes all I have with my crappy tool to loosen the lock ring) but the cup itself seems to have unscrewed quite a bit.

I didn’t remove the fixed cup when I stripped it down, and the fixed cup is still, erm, fixed. So it is definitely the non-fixed cup.

So how is the non-drive cup loosening when the lock ring is tight? I suspect I’m doing something stupid, but I can’t see what.

Thanks in advance.
Never be tempted to race against a Barclays Cycle Hire bike. If you do, there are only two outcomes. Of these, by far the better is that you now have the scalp of a Boris Bike.

Posts

  • veronese68veronese68 Posts: 24,349 Lives Here
    Long time since I've played with one of those so bear with me. If you are tightening the lock ring there's not much you can do wrong that I can think of. The lock ring is suppose to press up against the BB shell which puts a greater side load on the threads of the cup stopping it coming undone. If the cup is still coming undone is the lock ring pressing against the BB shell properly or is the thread damaged which is making it feel tight when it isn't? Is the thread in the BB shell damaged? Having checked all the threads I'd be tempted to clean them up and use a bit of Loctite, shouldn't be needed with a lock ring but if it's needed why not?
  • Cheers. I’ll try that. What “colour” thread lock would give the best compromise between fixing in place and actually being able to undo it at a later date?

    The bike is 20 years old so I guess the bottom bracket threads could be quite worn, although they felt fine as I was playing with it.
    Never be tempted to race against a Barclays Cycle Hire bike. If you do, there are only two outcomes. Of these, by far the better is that you now have the scalp of a Boris Bike.
  • veronese68veronese68 Posts: 24,349 Lives Here
    I think blue is the one that can be undone again. 243 I reckon
    http://www.loctite.co.uk/loctite-4087.h ... 2623520769
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