Forum home Mountain biking forum MTB workshop & tech

Threaded Bottom Bracket Issue

alikochoalikocho Posts: 6
edited May 2018 in MTB workshop & tech
I'm looking for some advice on an issue I have with a bottom bracket.

I recently acquired a second-hand Trek Liquid 20 (2003). It has been upgraded with a Deore crankset, with a shimano threaded bottom bracket. I noticed that the bottom bracket had movement, and with closer attention that the cups were spinning in the frame.

I've just removed the cranks, and discovered that the threads in the frame are gone. Not just stripped, but it appears that there must originally have been a threaded insert bonded into the frame (there is a recess, and there was a lot of fragment metal) and the bb cups were just loose, and being held more or less in place by the cranks pushing them together.

Ideally, I'd like to avoid the square taper route and keep the crankset.

My question's are then:

1) is it possible to replace what appear to have been threaded inserts in the frame?
2) would gluing BB cups in be a viable, albeit permanent option?
3) does there exist a part that I can pass through the bottom bracket and then screw the cups into holding it all in place like a square taper, or akin to a press-fit to threaded converter?

Any advice would be greatly appreciated.

Posts

  • keef66keef66 Posts: 13,123
    Do you know if it originally had a threaded BB shell? I'm trying to remember when press fit and BB30 bottom brackets started appearing.

    I'm wondering if somebody's tried to bodge threaded bearing cups into an unsuitable BB shell just to sell the thing? Maybe the metal bits are the remains of the BB cup threads and the BB shell is OK, and the recess is for drop-in bearings like BB30?

    If the BB shell itself is damaged I'd say have a competent bike shop look at it before throwing any money at it.
  • alikochoalikocho Posts: 6
    Original BB, according to the Trek archive was bontrager Isis splined. I believe those are threaded.

    Yes, the metal fragments could be where the cups have broken down, but they seemed to be rather more ferrous than alloy.
  • keef66keef66 Posts: 13,123
    ISIS splined suggests it was a conventional threaded BB :(

    If there's no sign of the original BB threads there are some threadless cartridge type BBs which screw together to draw them into the shell. But they are square taper. And I imagine you'd need to be sure the BB shell was the right size.

    http://www.gbcycles.co.uk/p/47132/YST-T ... VkQAvD_BwE
  • 02GF7402GF74 Posts: 1,294
    Can you not get your money back? Sounds like you may end up spending a lot of time and money trying to fix this.
Sign In or Register to comment.