Shimano UN73 BB users::::
 

Does the non-drive-side of your bottom bracket stick way out of the shell? I just installed one today on my new frame and the little plastic end sticks out close to a centimeter! This does not seem right! (Frame is a 2005 pista concept)

Thanks
Alex

you bought the wrong length

did you get a MTB 73mm shelled one?

the NDS "cup" does stick out some times, but not by 1cm.
if you got the correct 68mm one, then maybe your BB threads require chasing. happened to me with a KHS frame.

I dont think so. its 68x107.

A

Ah. Sorry. Didnt read your post correctly.

You probably need your bb threads chased further. This should take care of it, but maybe not...

Have you unscrewed it then reinstall?

I'll have to try it once more. I gave it two tries today. The point where the left cup gets tight is dependent on how far in Ive threaded the BB body, so Im not running out of thread. I guess the cup and the body could be mating incorrectly but that seens weird too!

Thanks

A

yeah, chasing threads will fix that.
you describe the exact thing that happened with my frame + BB
i could thread it in by hand when the BB wasn't installed, but it didn't want to go in more than half way otherwise.

That doesnt make sense to me but ok =)

didn't make sense to me either at the time. but it worked.

this happens a lot in the shop. Force it in.
Sounds like bad advice, I know, but the threads of the plastic cup deform a bit as you screw it in and it feels like you've bottomed out in the BB shell, so just keep cranking on the left cup and a few turns after you swear you've messed something up and the cup will free up and spin into position normally.
You won't mess anything up doing it this way. Even though it sounds scary, the plastic cup threads would be the first and only thing to screw up in the event I was lying to you:p

Don't ride with the cup sticking out that far. depending on how little thread you have engaged, you run the risk of slipping the cup on the left which will, in turn, totally trash the BB threads on the right. Also, you won't have adequate preload on the right side, which may allow the fixed cup to back out of the threads, leading to similar damage.

BTW, this is based on installing literally over a hundred of these units.

sometimes the BB shell/threads get cocked, and when you thread in the BB, it goes in at a slight angle. This could mean that on the other(adjustable cup)end, there is not enough clearance for the adj. cup to get in between the shell and BB, and wont thread in all the way. However, when the BB is not installed, it goes in just fine.

A.T.N's method of forcing it in, and having it free up later could be a symptom of what I mentioned. YOU could force it bast the tight spot, and the it would wedge the BB back to center and allow the adj. cup to pass through.

The plastic cup , not the BB, is going in cockeyed despite engaging the threads correctly. It's because the plastic cup deforms as it interfaces the BB body which is already in alignment. Just keep turning it in and the fixed body of the BB will force it back into alignment.

i have an alu cup on mine. all the same, i had to make sure that it was going in straight several times, and I had to use a good deal of force to get it in. the threads were greased and i made absolutely sure i wasn't crossthreading it into my mark v.

this bb has superceded my expectations.

When did Shimano UN-7X series turn to using "plastic" cups? (this is sarcasm for those who do not recognize it)

There is often thread lock gunk on the cups, so it gets harder and harder to turn the cup as it is inserted deeper. Dirt on the threads on the BB shell or the cup will make it harder to turn, first try cleaning. Also, is the BB new? sh1t on the inside of the cup or on the outside of the cartridge shell will seize things up. Grease the lead in on the cup, there may be just enought misalignment that the cartridge shell is hitting the edge of the cup instead of sliding in. loosen the drive side a few turns (so that the BB will wiggle a little) and try installing the non-drive side cup. If you are replacing the BB on your bike, there is less chance that the BB shell threads need chasing. If you are cross threaded, it will sieze up in less than 3 turns, inspect the ALUMINUM cups andthe BB shell and seek professional help if they are crossthread.

i hate how stuff like this would be so useful to know, but is so hard to read without parts in front of me. ah, well, i can find it when i need it later. search function, how great thou art...

conclusion: The BB Core was the correct 68x107, but the plastic cup was the incorrect 73 version. so the bottom bracket was in proper alignment and all that, it just had an extra 5mm of plastic on the left side!

ANNOYING! BUT SOLVED