Bottom bracket threads issue

Posted on
  • Alright everyone,

    Potentially a bit of a weird question here but I’ll try to explain as best as possible.

    Fixing up a mates bike and taken the bottom bracket out for a re-grease, upon taking it out (un55) the main body is all okay, but the left hand cup has lost just under half its threads due to a small nick from where the chainstay attaches in the bb shell.

    Apart from this small nick I cant seem to file out, the shell is great thread wise. Now if I screw in the left hand cup first all the way in with a nice amount of grease and torque down and then put in the main body that can screw in perfectly would this be sufficient.


  • The way to sort it is to run a bottom bracket thread chasing tool through to remove the “nick”.
    Any bike shop should have kit that can do this easily. If you’re simply refitting the old
    BB and greasing the threads you should screw the r/h side in first then the left. If you do it the way you’re suggesting the r/h cup won’t be tight and may well work loose.

  • This was my thoughts on getting rid of the nick okay so glad to know it should be pretty straight forward!

    Yes sorry got the order the wrong way round been a while since I’ve fitted one of these bb’s, if I decide not to get the bb chased as that would run up a new bb aswell, would this be a safe setup keeping as is, assuming it’s all torqued to spec?

  • Is there anything wrong with the BB that’s in there now, other than the thread damage?

  • Nothing at all it’s buttery smooth, only issue is the left hand cup having the first half of threads missing but the rest that are intact and screw in nicely.

  • What kind of bottom bracket is? You should chase the threads if a new bottom bracket is going in but with the same old one it won't get any worse.
    I'd probably still ride it assuming there's enough thread but for someone else I would do it right.

  • Sounds about right, yes may end up just getting it chased and sticking a new bb in there just for peace of mind, unsure if the current bb had any issues as I haven’t personally rode it, and didn’t want to cause any potential issues by fitting and unfitting the current bb multiple times.

  • For anyone wondering, I ended up taking to frame down to my lbs and getting it chased!

  • I was wondering if anyone can help. I recently bought a frame and it came with a Campagnolo Athena BB marked as 1.37" X 24 tpi.. I want to change to a Shimano Hollowtech II BB and cranks.. am I right in thinking it's Italian threaded? I bought a Shimano one off eBay but the diameter is too large.. can someone tell me what BB to order?


  • 1.37" X 24 tpi

    That’s normal bsa thread size. Was the hollowtech one that was too large Italian?

  • Despite being Italian, Campag stuff came in ISO / English sizes as mentioned above.

  • Yeah seemed to be..

  • What about the hread directions?

    Pretty sure you have an italian ht2 bb and a bsa/iso/english frame.

  • The BB shell will be 68 mm for ISO and 70mm for Italian...

  • Italian bb threads are clockwise on both sides but bsa is counter clockwise on the drive side and clockwise on the nds. You could use that to quickly check what the original is.

    Or measure as above suggestion. All good!

    Edit: but it does sound like you just need a bsa bb

  • Thanks, yeah I think it's 68mm, so will get a English thread for it and see..cheers for all the help

  • Post a reply
    • Bold
    • Italics
    • Link
    • Image
    • List
    • Quote
    • code
    • Preview

Bottom bracket threads issue

Posted by Avatar for Qebrus @Qebrus