Installed it torqued to specs. 1200 miles later and it has performed as expected.

The UN55 (73x118) I just received has the same issue. The left cup (ID 31.1mm) is quite loose around the shell (OD 30.5mm). There is a shoulder (ID 29.1mm) in that cup that will bear against the chamfer on the end of the shell by some fraction of a mm when both ends are screwed tight. That might be what supports the left side but it does not seem like much.

In my case I will need some spacers (to get my chainline right) so that shoulder will not touch the shell which will then be hanging free supported only by the drive side. I will make a shim to make the left cup fit snugly around the shell.

The UN 52 (73x114) that came out of this particular bike has a plastic cup (ID 30.0mm) that fits without play on the end of the shell (OD 30.0 m).

So the OP and I have an issue and attempting to understand it is not OCD. Those that don't have the problem and don't believe that the problem exists can go ride if they wish. Those with the problem, those who understand the problem and especially those who have a solution to the problem are encouraged to stay here and try to figure it out. :notamused:

The nds cup does not have a lip so you can thread it in below flush in the bb shell. There should be no need for a shim.

It is enough, and if you read the OP's update just above yours, there is no problem and everything comes together as designed when torqued down. No need for shims or spacers.

The aluminum left side cup I received with the UN55 has a lip.

Interesting. I've used UN-XX bottom brackets from 71 down through 52 with both metal and plastic nds cups and none of them have ever come with a lip. The only cartridge bottom brackets I've got with a lips on the nds cups are Octalinks.

JBC353- is it snug when torqued down?

Photos:

http://i926.photobucket.com/albums/a...ycles/un55.jpg

For comparison here is the UN52 that was in it.

http://i926.photobucket.com/albums/a...ycles/un52.jpg

I did not fully install the left cup as I saw I was going to need some spacers to get a better chainline.

This would be a lot easier with cup and cone.

And how many different kinds of beer am I going to have to drink to find the right thickness of can to make a shim out of? And will I remember what the problem was by the time I find the right can?

Just enough beer that you no longer worry about it:beer:

Well its in. And I have done 20 miles on it :thumb: But it just does not seem right that there is little support on the NDS. So Ill just keep on worrying about it for the next 20 years until it fails :twitchy:
http://bikeforums.net/attachment.php...hmentid=339450

Sorry, I mistakenly started a new string when I should have added it to this one. This problem with the Shimano BB-UN55 is real, the concerns are not OCD or excessive and flip answers are not helpful. The concept that the NDS cap will shrink to hug the cartridge is nonsense. If you can thread it in by hand, how can it "scrunch"? Also, aluminum is not flexible in that way. The clearance between the NDS cup and cartridge body is excessive, period. This slop will allow the cartridge to move up and down as you pedal. The laws of mechanical engineering are not subject to revision by rhetoric or marketing.

Sorry for ranting. Below is my post, repeated.

I'm a Clydesdale and I need a strong BB. Can't afford to put Phil Woods on my 5 bikes.

Recently I bought a shimano BB-UN55, happy that they have replaced the plastic left cap with aluminum, although I would have preferred steel. I immediately noticed that the left side cap fit VERY loosely on the cartridge. There was more play in this than I have ever experienced in an NDS BB cap. I called Shimano customer service and they said not to worry about it. I was skeptical but installed the bottom bracket anyway and kept an eye on it. I was properly torqued to 55 ft.lbs. It immediately worked loose, so I reinstalled it with blue thread locker. Soon, it began creaking like crazy. This is a 27 year aluminum frame so I’m worried about the threads in the shell. The BB55 left cap which does not hold the cartridge firmly parallel to the shell allows it to flex. I confirmed this by putting a run of plumbers’ teflon tape around the cartridge as a guage of whether there was movement and where. It was abraded away at the top and bottom indicating to me that the cartridge was lashing up and down while riding. Had the NDS cap fit snugly on the cartridge, it would have conrolled this movement. I replaced the aluminum left cap with a leftover steel Tange NDS cap which hugs the cartridge snugly. It seems to be OK.

I might use the Tange LL-3922 BB from now on. They only cost a couple of dollars more and I think all steel is a more robust way to go.

Yes, the Tange LN-3922 is my preferred choice also. LN-7922 is with Aluminum cups for those that like that .

Everything about them is better quality than the UN-54/55's. You do get what you pay for here.

Here is a photo of the inside of the left cup after being torqued to spec.

http://bikeforums.net/attachment.php...hmentid=341839

You can see where the end of the cartridge crushes the aluminum shoulder in the cup. In my opinion it is not much support for the left side. When I complete this build I will shim around the cartridge to make a snug fit.

I wonder if this is Shimano's solution to the issue of axial alignment. If the the BB is not threaded or faced perfectly the left end of the cartridge may not be exactly centered in the BB shell.

Shimano UN-54/55 are not designed to be adjustable in chainline, that's why the have the lip on the left cup. It's not needed at all, but they chose to add it. This is another reason why I do not choose their BB's. Yes, you can add spacers on the right, and I have(no more than 1.5mm) but you'll notice the left cup can't go in any further of course. It's not that big of a deal really, performancewise, as the left side on the cartridge really only needs to be stabilzed, it has nothing to do with the actual bearings spinning.

Yep, I agree. I would not attempt to use spacers with the UN55 unless I shimmed the left side cup to fit snugly around the cartridge. The contact between the cup and cartridge only begins within about 1/2 a mm before the lip bear against the face of the BB shell. With even a single 1mm spacer the left side of the cartridge would be hanging free and supported only by right side threads.

If I needed several spacers to correct the chainline I might use the 73mm UN55 if all the arithmetic worked out.

Seriously, I would not buy another Shimano. The Tange LN-3922 I mentioned is full adjustable, no silly lips on the left side . The left cup fits nice and snug, the whole unit exudes quality.

http://bikeforums.net/attachment.php...hmentid=341854

what bike is it? I just put one on my old 80's Batavus last night. The original bb had two spacers on the non-drive side and one on the drive side. Initially I did not use these, and i was not able to get the new bb to tighten, so I took it apart, put the spacers on the new bb and it fits fine. Not crazy about the steel spacer rings on an aluminum bb, but I'll deal with that later.
Take a measurement on your bb and see if it's shorter than 68.

That lip on the NDS cup is weird and makes no sense for this application -- I had to dig through my UN55s to make sure I wasn't crazy. The 107 and 113mm models I have don't have the lip, but the 115mm one does. No wonder some of you were having trouble getting the NDS end of the bottom bracket to stay put after it had been torqued down.

The Tange BB looks good and the price is good. I see they are available from Ben's Cycle so I will give one a try.

I'm glad i'm not alone, here. Thanks for the insights. I've always used a 1mm spacer or 2 to tweak my chainline. This helps my old bikes work better. I now see that the BB-UN55 NDS cap has to be socked down up against the cartridge to hold it. This will always be a problem since the lip on the NDS cap will prevent it from reaching in all the way. Shimano has essentially re-engineered their product for reasons I can't figure out. They have fixed what was not broken and broke it. The Tange NDS cap can be tightened in as far as there are threads in the shell. It is adjustable in any number of ways. i think for the additional $4 it's a better choice. And you're right, the Tange does exude quality. I hope Shimano is reading this and gets back on track with their BBs.

I bought a couple of Shimano BB-UN55 bottom brackets in boxes for projects I did not complete yet. I accumulated parts for several years so I don't know if this BB-UN55 problem is recent or not. Is there something I can look for to tell me if there's a problem? I tried them loosely in a frame to see if there's a problem and the two sides seem to go in snug.

I'm asking for clarification because I don't really understand everything in this thread.

Apparently the thread seems to indicate that, installed per manufacturer's instructions, they are fine. My actual experience corroborates that conclusion.

Unless your bikes require very long BB spindles, it would be better to use the next size longer rather than adding spacers.