UN55 bottom bracket keeps coming loose.

I've got an old Kona, steel frame with a UN55 sealed cartridge bottom bracket, like this one with the metal left hand collar/cup:



I could feel some play in the bottom bracket and at first I thought it was the bearings that had worn out, but on inspection, they were fine and the left cup had come loose, allowing the whole thing to move around in the bottom bracket shell.

I tightened everything up and all was fine, for a while, then it became loose again, so I tightened it again and gave the spanner an extra shove to make sure it was good and tight, and a few weeks later, it's loose again.

I've never had this issue with cartridge style bottom brackets before, It did occur to me that most of the previous ones I've had have had a plastic collar/cup on the left hand side, so I might have a look in my parts box to see if I've got one of those kicking about. Other than that, I'm not sure what to try, any suggestions?

This usually indicatea threads in frame bb are worn, odten happens on steel framea where the bb has rusted

Strange. Can't see why it would loosen if it is nipped up tight. If it was Italian thread, then that would be
a little more understandable. Anyhow, try with some Loctite thread locker instead of grease.

Hi,

Like Woz i also recommend loctite 243. But if you cant find it, you can also use teflon tape, usually used for plumbing works, it should do the trick!

Cheers

poncho":ubn1wb8l said:

Hi,

Like Woz i also recommend loctite 243. But if you cant find it, you can also use teflon tape, usually used for plumbing works, it should do the trick!

Cheers

Click to expand...

Yep,PTFE works for me!Stops the loosening and eases removal,easy enough to clean out of the threads too.

Re:

Thanks chaps, I've got some PTFE tape, somewhere, so I'll give that a go first and see how I get on.