External BB installation very tight to screw in

dodgyknees
dodgyknees Posts: 148
in MTB workshop & tech
Hi. I am upgrading the BB on my 29er mtb from a internal SRAM powerspline to a SRAM DUB external BB. The bike is only about 18mths old so the internal powerspline has come out relatively easily. I then cleaned the area of the frame thoroughly and applied grease as recommended, but when I go to screw in the new DUB BB both side cups only screw in by hand a little over halfway before becoming very tight.

In all the online help videos I have watched, quite a few now (sigh), the external BB's have screwed in by hand pretty much fully before needing the tool to tighten them. As such I am a bit concerned about using the tool and exerting all that force when the cups have got so tight so early by hand. Is this tight fitting by hand normal, and should I therefore proceed to tighten with the BB tool?

Comments

  • veronese68
    veronese68 Posts: 27,692
    Obvious question first, you have got them the right way round, having got the old one out you clearly know one is a left hand thread. If they've gone in half way it doesn't sound like you've cross threaded them either. I'd cautiously use a tool on them, don't use too much force.
    Kinesis Pro6
    Marin Nail Trail
    Cotic Solaris
  • dodgyknees
    dodgyknees Posts: 148
    Yes, got them the right way round and both sides do screw in by hand quite smoothly but only about halfway before they stop.
  • veronese68
    veronese68 Posts: 27,692
    Try it carefully then, could be a slightly damaged thread or something, seems odd that both sides do the same. Don't force it, just a bit more than you can apply by hand. You could wind the old ones in and out a few times to clean out the threads first.
    Kinesis Pro6
    Marin Nail Trail
    Cotic Solaris
  • Sut
    Sut Posts: 3
    edited April 2023
    Is there thread lock on the BB cup threads? that will make it harder once it gets to that point.
  • dodgyknees
    dodgyknees Posts: 148
    There is a kind of coating on the top threads of the BB cups, but on one side it doesn't seem to get that far before it tightens up.
  • whyamihere
    whyamihere Posts: 7,712
    I'd try it with the tool, but be very careful, it should be pretty free being screwed in most of the way. If it's still very difficult to screw in, you'll probably want to take it to a competent bike shop for the threads to be chased.

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