UN-54 B.B no-no.

[fixedfixer]

Assuming two things, 1) it's the correct thread, 2) there is sufficient thread within the bb shell, then you could try the following:

Clean the treads inside the frame, put a light coating of grease on them and the bb threads. Then as you thread the bb into the bike by hand (or use the tool to get better grip - but still by hand), when you feel resistance turn the bb one way then back again. Keep doing this and you will find the point of resitence moves a bit each time allowing you to thread the bb all the way home.

In my experience continuing to winch up a tread that is giving you resistence means the force will either break something or result in the part getting totally stuck.

 

[WJHall]

68mm is diameter, not length... ...

No, 68 mm is the BB shell length, or width (it is across the bike). The thread diameter will be about 37.

 

[WJHall]

Assuming two things, 1) it's the correct thread, 2) there is sufficient thread within the bb shell, then you could try the following:

Clean the treads inside the frame, put a light coating of grease on them and the bb threads. Then as you thread the bb into the bike by hand (or use the tool to get better grip - but still by hand), when you feel resistance turn the bb one way then back again. Keep doing this and you will find the point of resitence moves a bit each time allowing you to thread the bb all the way home.

In my experience continuing to winch up a tread that is giving you resistence means the force will either break something or result in the part getting totally stuck.

Very good advice, these large diameter fine threads are very easy to damage and you ought to be aiming to run them in almost all the way by hand, which you should be able to do using the technique above. It is true that once you are convinced it is fully engaged and the correct thread, you can accept the kind of stiffness that needs a spanner but this should never feel as though you have come to a dead stop, or are busting a gut, just a need to apply more torque than you can do by hand.

Bikes are delicate things, almost the only thing that should need real force is taking an old fashioned screw-in free wheel off, and then only if you forget to take it off and grease the thread when the bike was new.

WJH

 

[WJHall]

No, 68 mm is the BB shell length, or width (it is across the bike). The thread diameter will be about 37.

Actually I think I meant 1.37 inches diameter, which is actually about 34.8, so not strictly wrong, but not exactly right either.

WJH

 

[PpPete]

The threads on cartridge BBs are longer than those on some old fashioned cups. So, although the first bit of thread is easy, you end up trying to use a bit of thread that was probably never cleaned properly in the first place, and has had decades of gunk on it since.

Try cleaning the shell again, using lots of WD-40 and a small wire brush. Make sure you get all the crap out and try again. If still no joy, re-tapping is the answer.

 

[WJHall]

The threads on cartridge BBs are longer than those on some old fashioned cups. So, although the first bit of thread is easy, you end up trying to use a bit of thread that was probably never cleaned properly in the first place, and has had decades of gunk on it since.

Try cleaning the shell again, using lots of WD-40 and a small wire brush. Make sure you get all the crap out and try again. If still no joy, re-tapping is the answer.

Interesting comment, it makes me feel justified in the refit I just did, in association with a new chainset, where I used new old fashioned cup and bearing set and axle in a 1984 Holdsworth Claud Butler frame, both from SJS cycles, or possibly the more traditional sort of LBS.

I think the parts cost about the same as an integrated BB even allowing for buying a second axle due to getting the size about 1 mm short the first time. Also they will last much longer than an integrated BB, I believe that the regreasing interval (~ 5000 miles) for an old style BB is about the same as the life of an integrated BB. Plus you avoid the farcical performance of needing two people to take it out because the tools do not really fit the cups.

Old frames - old style parts, simple!

Retapping sounds a bit drastic, unless the thread has actually been damaged, perhaps you meant chasing?

WJH

 

[e-rider]

68mm is diameter, not length... but I had a similiar problem once and found that it was because I had tightened it all the way in on the drive side first. The non drive side refused to go in more than about 2/3rds of the way.
I loosened both sides off completely, then tightened the drive side halfway before tightening the non drive side most of the way. Finished off the drive side, then the other side nipped up no problem.

no idea why this was so, but it worked for me.

for a start 68 is the shell width, not diameter.

 

[e-rider]

Assuming that you are not doing something stupid, the most likely problem here is that the thread is no cut far enough into the frame (as someone has already mentioned). This is easy to check, remove the BB and look/measure how far the thread is cut into the BB shell; compare this to how much thread is on the new BB. What is the answer?

You are putting the RH side in first (which has a reverse thread) and then the LH side?

Are you sure both shell and BB are both english thread?

Are the threads clean?

 

[2Loose]

for a start 68 is the shell width, not diameter.

Already corrected by WJH...a long time ago.

 

[MartinC]

This sounds like paint in the BB shell threads. If the BB fitted before had steel cups they're not as deep as the alu UN54 cups you're fitting now. So you'll screw it in easily in the first portion of thread where the steel cup has cleaned the threads then you'll struggle when you hit the paint. I'd take it out and put a BB tap through the shell to chase the threads. Or take it to your LBS.

 

[Dan B]

Last time I tried this (early 80s Coventry Eagle) I found that the cartridge was stopped against a protrusion into the shell from the derailleur cable guide on its underneath - obviously the traditional cup bb didn't foul on it, but a cartridge bb more or less requires the shell to be completely empty of obstacles. Not saying this is your problem, just another thing to check.

For that particular bike it was easy enough to remove the cable guide anyway as I was converting it to fixed (so would have no gear cables needing guiding), but I don't know what your options are for aftermarket cable guides

 

[PpPete]

Last time I tried this (early 80s Coventry Eagle) I found that the cartridge was stopped against a protrusion into the shell from the derailleur cable guide on its underneath - obviously the traditional cup bb didn't foul on it, but a cartridge bb more or less requires the shell to be completely empty of obstacles. Not saying this is your problem, just another thing to check.

For that particular bike it was easy enough to remove the cable guide anyway as I was converting it to fixed (so would have no gear cables needing guiding), but I don't know what your options are for aftermarket cable guides

Good point. I've experienced this too. One can usually take out the cable guide screw and file it down so that cartridge will go in.

 

[MartinC]

Last time I tried this (early 80s Coventry Eagle) I found that the cartridge was stopped against a protrusion into the shell from the derailleur cable guide on its underneath - obviously the traditional cup bb didn't foul on it, but a cartridge bb more or less requires the shell to be completely empty of obstacles. Not saying this is your problem, just another thing to check.

For that particular bike it was easy enough to remove the cable guide anyway as I was converting it to fixed (so would have no gear cables needing guiding), but I don't know what your options are for aftermarket cable guides

Hmmmm. Yes this often happens. You usually find this out when you try to insert the cartridge unit into the shell not when you try to screw the cups in.