Garthr

With cartridge bearing BB's from Shimano, Tange, and IRD(Tange also) , you have to study the charts of these before you make that decision. The next size large is sometimes the same drive-side distance ! And sometimes it's too much to go to the next size. The charts are invaluable for all, look very closely at them
BTW, the Tange 111 in the chart is a 110 , and the 113.5 a 113. Don't ask why ! Shimano is just as odd .


https://web.archive.org/web/201010220...ttom-brackets/

jodphoto

Well, the manufacturers' instructions leave this potential problem out. Also, I still can't fathom why they would design this limitation in after a long successful product design history. You'll understand why after installing a fair number of bottom brackets, I don't read the teeny little Shimano-ese instruction sheet.

JBC353

Get yourself a metric dial caliper and start measuring. Ask yourself "In the context of my particular application, what holds the left end of the cartridge?"

jodphoto

You are definitely right about that. If it were a straight replacement that would be the way to go. Generally these issues come up when I am experimenting and parts swapping to see what will work best. You know, Frankenstein didn't fit together all that well, either.

jodphoto

The actual measurement of the spindle is a good starting point. With square taper BB's, though the actual place the crank ends up varies with each taper. So, it's not possible to measure this exactly without the BB and crank installed. Then you first get to see how far off you are.

AnkleWork

What potential problem . . . failing to follow the instructions? It would be a little over-recursive for the instructions to say "Don't ignore these instructions." to those already reading them.

Have you installed enough BBs to have seen DS plastic cups, NDS plastic cups, metal cups with flanges, metal cups without flanges, etc. ? . . . They don't all have the same installation procedure. But maybe you understand better than the manufacturer because you have installed so many.

hybridbkrdr

Does anyone mind making a Youtube video to show what they're talking about?

I re-read this thread and it's pretty confusing. (I can see people taking crazy pills reading this...)

jodphoto

I'll try to clarify what the issue is. Generally, most square taper cartridge type bottom brackets (BB) are all installed in a similar way.

The crank side or drive side (DS) threads into the frame and seats against the right face of the bottom bracket shell.

On the other side of the bike, the non-drive side (NDS), a cap threads in to the frame and it reaches in far enough to keep the cartridge from wiggling when you pedal. Traditionally these caps held the cartridge in alignment because they fit over the cartridge very closely, like a sleeve.

In the past, you could adjust the exact positioning of your cranks (adjusting the chainline) by adding spacers (say, 1-2 mm) between the DS of the cartridge and the face of the shell. Then you would just thread the adjustable cap on the left side (NDS) a little further in to compensate. Your bottom bracket would be a little further to the right and the chain line would be where you want it. Also, in past BB's the tight fitting NDS cap would hold the cartridge in alignment just because it gripped the cartridge snugly, preventing wiggle.

With the Shimano BB-UN55, the left side (non drive side NDS) cap does not hug the cartridge as tightly as the traditional BB's that came before it. There is a larger amount of space between the cartridge body and the inside of the NDS cap than on previous BB's. The only place this NDS cap comes in tight contact with the cartridge is at the very bottom of the inside of the cap. Unless this cap is socked down tightly over the cartridge, the left side of the cartridge is not being supported. The only support for the cartridge body would be the right side threaded into the frame.

Also, the new BB-UN55 NDS cap has a lip which prevents it from being threaded deeply into the frame. If you were to install spacers to move your crank a little to the right, you may not be able to get the NDS cap screwed in deeply enough to reach the cartridge. In the BB-UN55 the cartridge must reach the bottom of the cap or it will not be held in alignment. The cartridge could then wiggle, maybe loosen up, maybe damage the threads in the bike.

All of the discussions in this string revolve around whether or not this is a design flaw. Those people who have not had problems have tended to dismiss these concerns. I and others who have had problems (or are concerned that problems will arise) are retrofitting an older NDS cap, OR hoping for the best, OR avoiding the product altogether.

I hope this is an accurate and neutral appraisal of the issues and hope it is clearer now.

jodphoto

I misspoke about this being a potential problem. It's a REAL problem. Shimano's instructions don't address this consequential design change and their customer service department was dismissive when I inquired about the loose fitting cap. My purpose here is to share technical info and observations with other bike people, not argumentative flaming.

I've actually never seen a DS plastic cup, you got me there.

JBC353

Jodphoto, excellent synopsis of the issues. Frankenstein..

AnkleWork

Did you also misspeak when you acknowledged you installed the BB incorrectly? That is the "REAL problem." Shimano's instructions can't address the fact that you want to misapply their product. Can you guess why you perceive their dismissiveness? Maybe it's you.
If you want an adjustable chain line, why don't you just get an adjustable BB? That's so much easier than fighting reality.

Garthr

There is no one to blame here. Shimano has been putting a Lip on the NDS since the UN53. The UN54 also shares the Lip. Every so many years Shimano makes a succesor to the UN5X ascending.

When I first tried a UN54, I ordered it online and did not realize the lip was there, as I had used UN72's in the past, which were good cartridge BB's with no NDS lip, and aluminum cups. Actually, I can see why Shimano would include the lip. Because at full torque spec., I found it to cause some drag in Shimano UN72's. To prevent this, I can see why they added the lip then. I myself, do not follow their spec.'s, I consider them recomendations, becasue no two BB's or frames are precisely alike. Ever. Our bikes and parts are not truly precision instruments. There user always has to use their subjective mind to any application

So no one is to "blame"... ever. Okay, Shimano has it's reasons for doing as it does. Every user has their own expectations. If it's not working out, blaming doesn't make it work ! Refocus and assume you know exactly what to do, and it will come.

I, for one, am thankful for the experience as I discovered the quality Tange BB's, which are subjectively better in every way to the Shimano. I , like many people, didn't want to pay the extra few $$ initially thinking a BB was a BB, and "it's a Shimano, it will be alright". Okay, so it wasn't for me in this instance, it goes in my parts bin and I'll find a future use for it

jodphoto

All right...Peace friend, YOU WIN. If I try to defend my personality and grasp of reality, i won't have a leg to stand on. I'm going for a ride, now.

jodphoto

Thanks Garthr, this sums it up nicely. I hope everyone in the string and future readers take away that building and wrenching on bikes is a creative undertaking. A bunch of mechanically inclined bike builders can solve problems that engineers can't.

ThermionicScott 

If nothing else, this should be a reminder that Shimano's cartridge bottom brackets are designed for a 68 or 73mm shell width, and you MUST NOT increase that with spacers. Did anyone here have trouble with NDS wiggle without using spacers?

hybridbkrdr

I was contemplating starting my own thread to ask a question about it. There are already messages here on this topic so I'll put it here.

From what I understand, the lip on one side prevents you from tightening a certain amount. So, what happens if you want to install an SKS Chainboard?

https://www.sks-germany.com/?l=en&a=p...2d5d36a4769215



Let's say it adds 1mm to one side. So, if a 113mm bottom bracket is recommended, should I use a 115mm or 111mm? I'm not sure what the implication is here. Or, should I just choose a Stronglight or Sugino bottom bracket? I noticed a Stronglight model that doesn't have a lip on one side but I don't know if it's the side that would keep the SKS Chainboard in place.

I wanted to know also out of sheer curiosity, if there are some model Alivio cranksets that take either 113mm, 118mm, 123mm or 126mm axle bottom brackets, what's the point of having 123 or 126mm? Is it to keep the legs farther apart for recreational-level bicycles?

Garthr

The Chainboard does not require any change to a spindle length.

hybridbkrdr

OK, but does anyone know if it pushes the lip by 1mm, would I need a non-Shimano brand bottom bracket to make sure the other cup is tightened enough?

JBC353

The Chainboard will keep the left cup of a UN55 (at least the ones I have used) from mating with the left end of the cartridge so it will not be supported. With the UN55 the *effective* length of the BB shell must be either 68 or 73 mm.

pdxtex

OP, if you have the UN55 with the plastic non drive side cups, send it back! this is a known shimano design flaw and eventually the plastic will crack. shimano has redesigned their square taper bottom bracket and they have gone back to metal non drive side cups. find one of those....

ThermionicScott 

It's unfortunate, because the plastic was originally intended to prevent creaking, which is known to happen with the metal cups.

PMK

Picked up 2 UN55 bottom brackets for our Ventana tandem. The stoker BB is a 73/113 and the captain BB is a 68/113.

I noticed immediately the loose fit of the left side cup onto the BB shell.

My experience with BB installations has always had the left side cup as a good near zero clearance fit onto the BB shell. As described by others, there is a definite loose clearance.

I agree the design of, or manufacture of the left side cup is not correct. The reason I say this is that the entire inside surface of the left side cup is coated with a teflon like material. The purpose of the coating is to prevent metal to metal contact of the steel BB shell and aluminum cup. Also, the area where this coating is applied, matches the needed area of support for the left end of the BB shell.

The idea of the thin lip of the BB cup, pressing onto the end of the BB shell for full support does not even make sense when you see these parts in hand. I would throwback also that the replies that contend that there is a lack of understanding or an OCD should see the concern first hand. Yes it can be made to work, even if the left side cup is wrong. Seems kind of a hack install when it is obvious the coated inside surface of the cup was meant to handle the loads.

PK

jodphoto

When I am standing up pedaling, mashing up a hill, it's balls to the wall. I DO think about my BB. I DO NOT, however, wish to reflect on it's engineering.

It's a case of religion vs science. Some folks on the forum just simply believe in Shimano without question. Others add in craft, experience, engineering or common sense and continue to wonder.

This string has had a respectable amount of participation. The sum total of my understanding about this issue has come from this string; both from those who agree or disagree with me.

One would think that Shimano, with their marketing prowess would address this. Since marketing, in part, seeks to mold perception of their product; is a savings of pennies on a part, followed by a non-responsive stance, worth the potential loss of customer confidence? I wish that Shimano would weigh in on this. I think that their customers deserve answers and would welcome any information.

Meanwhile, the failure of, or uncertainty about, Shimano 26,54 and 55 BB's has led me to buy Tange LN-3922 BB's. I have not had problems with 3 of them so far.

After all, I'm just wrenching and riding. Don't care that much about marketing.

Happy Thanksgiving to you all.

ThermionicScott 

Are you going to blame Shimano for your incorrectly-installed BB on Christmas, too?

jodphoto

Scott,

Why are you so hell bent to follow Shimano out the window on this?

How many people need to express their misgivings about these parts before it becomes a legitimate concern by your criteria? Problem Solvers is making money by providing a solution for an issue you feel does not exist. Are they all wrong?

I have always tempered my remarks to keep within the considered boundaries of this forum. I learned that I made the installation error by reading this string. That is the value of the forum. We share information.

That information should have come from Shimano. It did not. Neither their instructions nor their customer service were helpful.

All I wish is that Shimano had responded in a way that gave technical support. I blame them for not doing that.