Shimano BB-UN72 Installation

[N/B]

A square-taper BB quandary;
I have an old but smooth BB-UN72 that I need to use on a build. The cups are in the opposite situation to how they're supposed to be, ie the Drive-Side cup is detached, and the Non-Drive-Side cup is stuck firmly on. I can't seem to tap it off with a screwdriver.

Sheldon's page shows that both cups on a UN72 are indeed removable.

So;
- Is it absolutely imperative that the Drive Side cup is installed first, or can I install it via the Non-Drive-Side first if I make sure I don't wind it too far in?
- Could this cause problems further down the line when I next need to remove the BB?

 

[The History Man]

As long as you get the drive side cup all the way in and the bb itself seated against it can't see a problem.

 

[marc two tone]

Re:

Yep, the non-drive cup seizes 9/10.. it will work fine though.

wind in the drive side cup into BB shell, all the way(the one on right in pic) pinch up tight.

Then, feed bracket in through non drive side, carefully get the threads to contact right.

wind in 'til it butts up against drive-side cup, job done. maybe threadlock both cups for reassurance.

 

[Osella]

^this.. Your other option is to install the NDS first, then put the driveside in as far as it will go. If it doesn't seat against the frame I've found in the past that turning it as hard/far as you can, then undoing the drive side again will bring the shell & axle with it, leaving the NDS cup in the frame; you can then install as 'normal'.

 

[hamster]

Earlier versions (UN70) were fitted with the NDS fixed on the BB and they never gave trouble. As long as it all goes together in the end I don't see why there would be a problem.

The biggest issue I have is finding spare NDS cups to replace those dreadful plastic ones on lesser versions.

 

[N/B]

The biggest issue I have is finding spare NDS cups to replace those dreadful plastic ones on lesser versions.

Problem solved, literally.

 

[hamster]

Thanks for that!

 

[N/B]

I'm still a bit stuck with my UN72 at the top of the page - I think I need to replace the cups (the black parts). They're both quite chewed up from previous install/removal and I'm worried about getting them stuck in my frame.
Can I source new cups from anywhere or is it a case of looking for old UN72s to salvage cups from?

 

[dyna-ti]

Warm it with a hairdryer