Incorrectly threaded bottom bracket

[n1ck5000]

I have recently acquired a perhaps early 90's Dawes hybrid. It appears to have been little used and is in generally great condition except that the bottom bracket is incorrectly threaded. The drive-side has a cup and lock ring and is 'normally' threaded - ie turning clockwise tightens the cup. The non-drive side is reverse threaded. I can only assume that this was a manufacturing dud, or would it have been possible for someone to have re-tapped the shell with incorrect threads? i took it out for a ride and the drive-side cup came loose after 10 miles. Any suggestions to stop this happening?

 

[raleighnut]

I have recently acquired a perhaps early 90's Dawes hybrid. It appears to have been little used and is in generally great condition except that the bottom bracket is incorrectly threaded. The drive-side has a cup and lock ring and is 'normally' threaded - ie turning clockwise tightens the cup. The non-drive side is reverse threaded. I can only assume that this was a manufacturing dud, or would it have been possible for someone to have re-tapped the shell with incorrect threads? i took it out for a ride and the drive-side cup came loose after 10 miles. Any suggestions to stop this happening?

No all English BB threads are like that whether BSA or Raleigh threaded.

 

[n1ck5000]

No they are not, they are normally the opposite, thus my problem!
The drive-side should be reverse-threaded and the non-drive-side threaded normally (clockwise)

 

[rogerzilla]

It sounds as if a bike shop muppet has put the taps in the wrong sides. This is really easy to do as they are marked L and R but this refers to the threading, not the side of the bike. This is the second case of this I've read about this month!

Options:

1. Loctite and hope
2. Ream and thread to Italian
3. Ream, sleeve and rethread to BSC/ISO
4. Threadless BB.
5. New frame

Try 1 then 4. Then, as an early 90s Dawes hybrid is of no real value, I would proceed straight to 5. Options 2 and 3 are about £90.

I've discounted retapping the correct way round as the threads are already very weakened.

 

[Big John]

I do one day a week for a bike charity and I've cleaned bottom bracket threads up with a Cyclus threading tool but never actually ever tried reversing a thread but maybe it's possible. If so then a trip to your LBS might be all you need to put your bottom bracket back to normal. I wouldn't think they'd charge too much for the service.

 

[si_c]

If it is threaded incorrectly then the best option is loctite and get it B@st@rd tight. I had a similar problem on an old steel frame with a french threaded bottom bracket - there was no reverse threaded option there at all. The only option was to get it really really tight.

 

[n1ck5000]

Thanks all, sounds like Loctite is the way forward, as the value of the bike does not warrant anything more, albeit that it's a lovely lightweight steel frame. I did wonder if maybe a cartridge bottom bracket unit (if I can get one with the right dimensions when inserted the 'wrong way around') might exert less turning forces on the cups than the current loose ball bearing setup.

 

[rogerzilla]

Probably not. The cup still tries to walk out of the threads. However, in a BB cup, it's not a huge effect (which is why Italian bottom brackets are found on top-end bikes and mostly work, even though they're "wrong".

 

[n1ck5000]

By way of update on this, I took the bottom bracket apart this morning and gave it a good clean, and the threads are a bit of a dogs dinner, evidently due to post-manufacture interference. Loctite applied and fingers crossed!

 

[si_c]

If it's a complete dogs dinner you could get a frame builder to fill the threads and rethread, not cheap though.

 

[midlife]

BITD the BB was cut across the bottom, pushed together and rebrazed. This reduced the diameter of the BB which was rethreaded properly again. Probably easier to buy a threadless BB lol