Brompton bb stripped threads


New Member
Hi, I have a Brompton with a jis 119mm bb. The bb got stuck, and in removing it on the drive side the threads on the frame got damaged. Tried to replace with a new cartridge but the plastic threads got ruined when attempting to, with the bb ending up at an angle.

Is there a threadless bb that will fit the Brompton? If not will a non plastic bb work as it will be harder to strip?

Trying to avoid replacing the entire frame as it's about £280




New Member
For the alternative I was think maybe a Shimano UN55 Square Taper Bottom Bracket


Legendary Member
Accra, Ghana
You could try taking it to a machine shop and asking them to re tap the threads. Your LBS might even be able to do it or advise on alternatives.


Casper WY USA
Far more likely to mangle plastic than steel. Shimano makes a cheaper BB with the non drive side plastic, and I have cracked that trying to tighten the non drive side. A little more expensive is one with an Al insert. My better Shimanos are fine..I have not yet worn one out. Remember the threads are reversed on the drive side. I put mine in greased to make it easier to remove them later If needed. As far as compatibility goes I used a $12 Vuelta one which continues to work perfectly. Be gentle seating the cups, though, although a good LBS should have thread taps for a bottom bracket.


Professional layabout
I try to avoid those BB's with a plastic end, they start to screw on then feel more and more binding after that, even on good threads.

I've had good results with Halfords own VP brand BB's, steel at both ends and only a tenner.

Last resort would be a threadless BB, can get these on Ebay readily enough
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