oj.

I recently bought a 1960's BSA road frame and I'm currently in the process of converting it into a fixed gear. The first problem I encountered was that the fixed cup was stuck in the frame, nothing a trip to the lbs couldn't fix. After having that problem resolved I went on to purchase a cheap non-branded square taper bb. This is where the problems started I could get the bb in about half way before having to resolve to brute force. I brute forced until there was about 5mm of thread left on the bb at which point i could not get it to turn any further. I then bought a shimano bb hoping that my problems would be attributed to the non-branded bb being defective. Unfortunately this was not the case and i had the same result although this time a opted not to use excessive force. From here I went on to search the internet hoping to find a solution to my problem, from what I read most people said that getting the bb shell chased was the best thing to do. After getting the frame back from the lbs a second time and finding I have the same result I am at a loss. What I want to know is has anyone else experienced the same problems or has any idea to what I should do?

Andrew R Stewart 

The first thing that comes to my mind is that the frame likely has a 26tpi shell and the current cartridge BBs don't usually come in this spec. So the Bbs you tried were 24tpi. The miss match of thread pitch needs 5-6 threads of overlap before they bind up.


Didn't the LBS mention this? In theory chasing the shell with a 24tpi tap set is possible. I wouldn't do this with my Campy tools though. Not when threadless BB units and Phil Wood are still options. Andy.

2lo8

You shouldn't brute force anything threaded, ever.

Grab a ruler and compare the length of the threads, get a cheap toothbrush to make sure everything is clean, and make sure you don't cross thread and try again.

Also, I don't know what you mean by a road frame, but BSA was Raleigh owned by that point. If it's a Nottingham frame it could have the Raleigh BB threading despite the BSA name. Sometimes those shells were even used by the Carlton factory on occasion.

oj.

the bike shop didn't mention anything about 26 tpi but I'll go compare the lengths.

2lo8

It would help if you said what frame you had instead of just "1960s BSA road frame"

Bike shop employees are not perfect experts that know everything about bikes.

oj.

I would also like to know what the model of frame is but the person i bought from just said it was a bsa and I can confirm that from the head badge.

oj.

I have just measured the threads in the frame, it was kind of hard to do with a ruler but the results I got were similar enough to that of the bottom bracket.

oj.

I am now almost sure that the frame is using Raleigh threading as the cup width is 71mm. what i would now like to know is should i buy a press fit bb or try to find Raleigh cups and a suitable spindle?

AlexCyclistRoch

From what you've told us, at this point the threads are likely ruined.

This is the difference between a real bike shop and a 'bike boutique'. Anybody at a 'real' shop should know that a 1960 British bike would very likely use non-standard threading.

2lo8

The good old "no real bike shop" fallacy

oj.

I have decided to buy a threadless bottom bracket as this is much cheaper than taking it to a frame builder and getting new threads cut.

2lo8

Were the cups you forced in metal or plastic?

oj.

Somehow the non-driveside cup (metal) went in almost all the way on the cheap bb without using excessive force. The cup i forced was the driveside (metal) with the cheap bb. The non-driveside cup (plastic) on the shimano bb barely screwed in at all.

Miele Man

Is there a bolted on cable guide under the bottom bracket shell? Sometimes the bolt for those will hit a cartridgee bottom bracket but not a fixed cup.

Cheers

oj.

nope, I shaved the frame.