ultramagnetic

The plastic cup of my Shimano UN-54 bottom bracket has been cracked ever since I installed it about 2 1/2 years ago. There is now a constant clicking sound that corresponds with every pedal revolution that used to come and go. I've convinced myself that the crack that extends all the way across the cup is the source of the click and am trying to replace it.

After finally finding a source locally for what I thought was the correct replacement cup, it appears that the replacements are taller/deeper by about three threads than the cup that came with the bottom bracket. It's a 68mm shell and the new cup was marked as being for a 68, so the reason for the extra depth I don't understand. Because of this, it won't thread completely into the shell. The mechanic at the bike co-op where they sold me the cup suggested to bring the bike in and fit a shim to make up the difference. I'd rather use a cup that fits properly and threads all the way in if possible.

Has anyone experienced this? Was there a change in the dimensions of the cup or the cartridge in the last few years? I'm hesitant to try to order a new cup online because it looks like what I bought in person is the same item available online. Should I put a shim on and call it day because the what Shimano now sells as a replacement doesn't actually work in all cases? I've thought about buying a new UN-55 with the hopes that the metal cup will fit my current b.b. which seems to be in good condition, using that cup and having a reserve b.b. on hand. And if the new cup doesn't fit my current bb, just install the UN-55 and be done with it.

Thanks.

Ferrous Bueller

Seems like the longer length is interfering with something in the frame, or the frame threads are not cut deep enough.
I'd shorten the new cup by grinding it down or slicing a bit off with hacksaw. The inside rim of the cup does not need to be perfect.
When you do tighten it in this time, don't use a lot of force.

ThermionicScott 

I wouldn't fret it if the NDS cup sticks out a little -- have you tried taking out the BB and just threading the NDS cup in to make sure it isn't catching anywhere?

fietsbob

Maybe there are a 74 and 68 wide compatible NDS piece,, to adapt the cartridge to mtb & rd BBs.


QBP has an "up Cup" essentially the aluminum NDS part from the higher ticket UN xy part.. FS separately..

LBS may have a bin of parts from BB replacements too ... "It's Still Good" .. Reuse..

ultramagnetic

The replacement cup threads completely into the shell. I checked that when I started having issues.

I know of the Problem Solvers cup but for the price I've seen them, I'd rather just buy a new bottom bracket. And I've seen replacement metal Shimano cups at Universal Cycles' site which are cheaper but I'm concerned about having the same size problems as the plastic cups.

And the LBS closest to my house that I went to first gave me a metal cup out of their bin that had the correct thread and shell size stamped on it. The problem was that the inside diameter of the cup was too small to fit over the b.b. cartridge. I wonder if that cup was the same metal Shimano cup that Universal Cycles sells.

AnkleWork

I installed a lower level Shimano BB that also left the plastic cup "proud" by about a mm, though it looks like more due to a chamfer in the shell. Like yours, it appeared to wedge against the taper of the cartridge. I just torqued it per instructions and used anti-sieze. That was over 15,000 km ago and it is still perfect.

How far does yours stick out?

Ferrous Bueller

If the pieces won't fit together at a 68mm width, one or both of them are probably intended for a 73mm BB shell, but mislabeled.
Or you've got an under-width BB shell in your frame. Have you measured?

ultramagnetic

The replacement cup sticks out over maybe 1.5-2mm with the cartridge full inserted.

I have measured the b.b. shell and it is 68mm.

Today, I went back to the shop that gave me the first replacement cup. They didn't have any in the leftovers bin that fit and the mechanic helping me claimed that Shimano doesn't sell replacement cups in order to force you buy a whole new b.b. because "that's how that make their money". If you say so, buddy.

I did take the cracked cup in along with the b.b. and looked at a new UN-55 off their shelf and compared the cups. The alloy cup is the same depth/length as the original cup. So it seems like the replacement cup could be for a 73mm shell.

I guess tomorrow I'll call up another LBS I've never used on the off chance they stock this stupid cup but I won't hold my breath.

Kimmo

Dude, there are at least two co-ops in your area.

https://bikecoop.ucsc.edu/

https://bikechurch.santacruzhub.org/

Check the link in my tag for more.

ultramagnetic

Yes, I know there are. The Bike Church is the co-op that I went to and purchased the replacement cup that doesn't fit. And I bought the cup after sifting through their bottom bracket bin for a used cup and not finding anything. And the University co-op isn't really an option because I can't get there during their business hours.

OneGoodLeg

For $18.99 I'd save myself the aggravation and just buy a new BB.

AnkleWork

Unfortunately, a new BB won't necessarily fix the problem. If the BB functions well I'd probably live with the slight mis-fit, after all the OP lived with the crack and click for two years.

Has the OP established that the click is not inside the BB cartridge? If not, then there's a great reason to install the new cup and ride the bike to see if the real problem is fixed.

ultramagnetic

I think I may have sorted this out. I think that the replacement cup that I was sold, and possibly what I've seen that is available online, is a 68mm cup to be used with E-type front derailleurs that don't clamp on to the seat tube but rather have a plate that fits between the drive side b.b. cup and the shell. The plate thickness might explain the need for a deeper non-drive side cup.

PHT

Have you tried the sunlite ones? I've used several without complaints. Retail cost 4 bucks, heh.

ultramagnetic

I don't think I ever realized that Sunlite offered components and parts. I thought it was just tools and accessories. So you have used those replacement cups with a Shimano UN-54?

PHT

Since we are mainly a utility/commuter/etc repair shop, usually we use the lower end UN-26 to save a couple bucks for the end user. I see no reason why these cups shouldnt work with the UN-54 (or currently UN-55?) however! I do believe I've done a transplant of an older UN-54 with the Sunlite cup with no problems but I cant say for sure. I always have a few on-hand because often times I get donor bikes with perfectly good older cartridge BBs, but stripped plastic cups. If you cant find a source I can facilitate, but any bike shop shop be able to order you one.

I would stay away from their tools but I see nothing wrong with most of Sunlite's repair parts for recreational, beater, or commuter bikes- especially for an item like this.

Continuity

Do you actually notice any functional differences between the UN26 and the UN54/5's?

PHT

I think it's mostly a weight thing, and I cant say for sure if one has smoother bearings than the other. Pretty sure it's hard to tell any difference once the bike is out on the road. I figure if anyone's going high end anyway, they wont be rocking square taper cartridge BBs. . .

400trix

With mixing and matching of NDS cups, I'd call that darned near perfect. I seriously doubt that it will affect how the bike works at all, and quite frankly matched NDS cups on UN26's usually stick out at least that far. Just get the cup snug, and all will be well.

400trix

The higher end BB's are both lighter and smoother. The Dura-Ace adjustable BB is a thing of beauty, and if Shimano made a crank short enough for me I'd use one, just because its so cool.