Need some advice on a bottom bracket problem I'm having. The non-drive side of my HollowTech2 BB worked loose without me realising it. I could feel some slop or play when riding, but thought it was just cheap pedal bearings and thought nothing of it, so continued to ride like this for a few months. (I've never had this problem happen me before; I'm always very careful to torque things up properly when putting things together.)

So anyway, I got the tools out to investigate. It seems like the BB cup won't grab the threads properly now. And it was the same story when I tried the cup from an old BB I had lying around the shed. How can this be fixed? It seems like this could be a specialist job, not something I could do myself.
Thanks,
Paul.

What is the frame material? It sounds like you stripped the bottom bracket shell threads (I assume it's English threaded). If it's a steel frame you could have the damaged threads built up with brazing material and retapped. If it's aluminum or carbon you are probably out of luck.

There are threadless bottom brackets that can salvage a stripped shell but they are square taper and would require a different crank. Here is one: https://velo-orange.com/collections/...ottom-brackets

Without actually seeing what the existing threads look like I would at least first try having the threads chased and try some loctite tape. You might be able to salvage what is there.

https://www.amazon.com/Loctite-13726.../dp/B004B6T4KG

The next option is to have the BB reamed and retapped to Italian. I don't know if HT II has a 68mm Italian thread cup though.

Not good news for my frame by the sound of it. Just my bloody luck. Beautiful frame for the bin


Frame is Aluminium (2005/2006 Giant ALUXX hydro formed 6011A alloy). BB shell width is 68mm (67.7mm after facing off.)


When you say Italian thread do you mean Campi or something? Might be an option, but that would mean I'd have to drop my XTR crankset. I'll also check out the threadless bottom brackets, and the re-chase and locktite options. Thanks for the ideas.


Would something like a helicoil insert repair kit be of any use? I know they can be used for repairing damaged spark-plug threads in engines, but a MTB frame is a very different kettle of fish. Here's a pic of a similar bike to mine, that has the same frame:

Not necessarily Campagnolo but just Italian thread spec, which is larger diameter than ISO. Shimano and others off cartridges in Italian thread. Most are designed for a 70mm shell width, though, which may cause chainline issues. Phil Wood, SKF and others offer cartridges with separate mounting rings that can avoid this issue.

Are you sure it is the frame that is stripped and not the cup?

There would not be a helicoil that I know of in that large or fine of thread

It is a shame to assume that the frame is a toss out now without having someone with experience take a look. There's a chance that a simple chasing of the BB threads and careful install (of a new BB) with LockTite might be all that needed to get a bunch more years of use. Here in the States chasing a BB might run $25 to $40 on a frame that has had the BB already removed. I've used various LockTite grades on BBs for years with pretty good results. It all depends on how bad any BB thread damage is really there and if there's not enough material to work with.

I would hope that there's a skilled and motivated shop near by that can assess this frame and give far better insight that we can so far away. Andy

I tried an old BB cup I had left on a shelf in the shed. It was even sloppier than the one I took out. It might just be worth trying out a brand new BB cup to set if it fits tighter and grabs the frame threads better. I'm wondering if it's possible that I don't just have damaged threads.... and that over the months the round BB shell got slightly ovalized due to the shifting pedaling forces?

... But, yeah maybe I was a bit premature to presume the frame was for the scrap heap.

So, a helicoil insert is a no-go, and a re-chase sounds like a good 2nd move. (Just to clarify... a re-chase on an aluminium frame just means a re-threading and clean yeah??).
If the rechase and locktite/bonding fails to resolve the issue, what does this threadless BB look like to you? :

68mm threadless BB https://www.sjscycles.co.uk/bottom-b...maged-threads/

If I go with a threadless system like this, do I need to grind out what little is left of the existing threads?
Thanks again for all the advice.

Have you tried plumbers teflon tape on the cup?

It reads to me that some of the challenge is getting any cup to start to thread in, to get that initial turn of thread engagement. This is where patience and skill came help. On the adjustable side using a cup lockring to insure the cup is coaxial (the lock ring is threaded down so it contacts the BB face during that initial thread catching effort) can help. Andy

...that was my first thought, but a few winds of the PTFE type would compress over time, and the slop would return I'm guessing?

Thanks Andrew for that trick with the cup lockring. I don't think I'll need it though, as this just arrived this week (wasn't cheap but should do the trick):



YST Corporation 68mm Threadless Bottom Bracket Set YST BB-0901.

Any idea why the SRAM installation option needs the two extra ring and collar fitments?



YST BB-0901 Instructions.

Tell that to a Plumber

Do you mean they swear by the stuff?

Anyway got this fitted last weekend and it worked well on its first off-road excursion as this pic shows!:



A 20min job turned into a 2hr one as usual. To anybody doing a similar repair here are just a few pointers:

- Put a tiny bit of copper grease on the internal threads of the new BB before screwing them together. It could be years before you remove them and you don't want them seized up.
- The large diameter conical ring (part #2 in the YST instruction diagram) only goes one way. Don't get it reversed or you will damage it on tightening.
- There is no need for any of the Shimano 2.5mm plastic spacers (2 drive side, 1 non-drive side for the 68mm shell). The YST dimensions compensate for these, so leave the spacers out completely. Not sure what you would have to do in the case of an E-type derailleur bracket....
- A little grease too on the inside of that narrow HollowTech adjustment nut to stop it binding to the crank arm as you screw it in fully to the home position before installing the left crank itself.
- The YST pushes everything out a little, so due to the new chain-line you will need to re-adjust the front shifter cable anchor/cable tension, and the upper/lower limit screws on the mech. Then re-index your gears with the barrel adjuster as normal.
- Inspect everything after a few miles.