Hollowtech II BB alternative for stripped frame threads [duplicate]

Question

I removed the BB (Shimano BB-93) from my Canondale Trail and found the drive side thread is stripped on BB and frame.

See and

What are the options for me to replace the BB?

Is there an alternative Hollowtech II compatible part which will reach the good thread or other alternative?

I'm aware there could be a machining/welding/tapping option, but would guess that would not be worthwhile on an ageing bike.

Are there any alternative parts I could use?

Sheldon Brown mentions a Velo-orange option that clamps in place, but if possible I'd like to keep my recently replaced Hollowtech II crankset if possible

I'm baffled by all the combinations, hoping someone has been down this path already and can suggest if there's a practical solution.

Answer 1

There is no easy or readily available option for this problem.

In my professional opinion, you should consider replacing this frame.

However, there are options if you really want to keep using this frame.

1. Ditch hollowtech and use a threadless square taper bb.
2. Bond the shimano hollowtech cup to the frame.
3. Weld and re-thread

Threadless BB thread to eachother and just press onto the frame. These work well for a while, but if you're not super careful, they can (slowly) further damage your frame until it's completely unusable.

Shimano hollowtech cups have a bearing pressed onto them, you can actually replace the bearings of the cups instead of buying whole new cups. This usually doesn't happen because the bb cups are relatively cheap and it does require some skill and non common tools for the job.

If you bond the cup to the frame (making sure it's aligned properly), theoretically, you will just have a "pressfit" frame. You can then use the cup and replace the bearing when it wears out.

Video demonstrating the bearings inside the cup

Finally, unless you have a welder or know someone with a welder who is willing to help you, it will probably cost more to fix this than to get a new frame. The bb thread cutting tool alone will cost more than the frame, and I would be extremely surpised if a bike mechanic is willing to use theirs for such a job. Also, the heat from welding is very likely to bend the frame and result in misalignment. This option is completely out in my opinion.