The threads in the MTB frame that is supposed to hold the bottom bracket lock rings were very loose and it can't hold the bottom bracket in place. The previous bike owner tried to apply Teflon tape in it but the lock rings still moves out of the frame if pushed from the other side.

Any recommendations on what to do?

  • Add more Teflon tape?
  • Convert to a hollowtech crank?
  • 2
    How about a photo so we have some idea what kind of BB it is. – Henry Crun Aug 5 at 7:39
  • Is it the right BB? Has someone fitted a 68mm threadded BB into a hole that needs a 70mm ? Could be someone's levered on it and stripped all the threads? Need to open it and clean and inspect to decide if theres physical damage or a bad fitment. – Criggie Aug 5 at 7:40
  • Also please give us the material of the BB shell - is it steel or alloy or CF or something else? Is it a nice bike or a junker ? How handy are you with tools ? – Criggie Aug 5 at 7:42
  • It's a tapred bottom bracket. And it's at a very bad condition to the point where you push the non drive side of the crank and it will push the bottom bracket out of its original location. – Kulelat Aug 5 at 7:47
  • There are many different bottom bracket shells (the part of frame where bottom bracket goes). We are trying to determine which one you have and whether you have wrong bottom bracket or something is broken. Right now the question does not have enough information for any kind of answer. – ojs Aug 5 at 8:17

A video could really help, sounds like the threads of the cups and/or of the frame shell are damaged. Probably the Bottom Bracket cups need to be removed so the threads can be inspected for damage, like rust, or cross-threading, stripped threads etc. If the threads of the shell are in good enough condition, they can be cleaned and a new BB installed. If the threads of the shell are damaged, then it would be a bit more complicated and deserve it's own question/answer.

This image (from Park Tool website) has the names of some BB parts. Even if it's not a perfect match, editing the question and using these terms would make the question clearer.

Bottom bracket part names by Park Tool

  • If OP is very lucky the cartridge BB threads have stripped rather than the frame. – Argenti Apparatus Aug 5 at 21:27

I haven't seen one in quite awhile but Sunlite made a repair bottom bracket. It looked like a standard sealed square drive unit. The cups lacked the standard external threads. One of the cups was part of the bearing housing (shell). The other cup had female threads. The bearing shell had Male threads that screwed into the female threads of the cup. By using two bottom bracket sockets you tightened both sides to clamp it to the frame.

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