Incorrectly threaded bottom bracket

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n1ck5000

Member
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

Legendary Member
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.
 

rogerzilla

Legendary Member
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.
 
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Big John

Guru
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

Guru
Location
Wirral
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.
 
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n1ck5000

n1ck5000

Member
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

Legendary Member
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".
 
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n1ck5000

n1ck5000

Member
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

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

midlife

Guru
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
 
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