bottom bracket toubleshooting trivia

[Scott]

Hey, Bunch:

Pinging the group's knowledge for input/feedback on an issue I'm having with an install of a new cartridge style BB in a new frame.

I'm building a new Atlantis and Gus. I installed a new BB (Shimano XTR UN91) in Atlantis and torqued to spec. It's butterlicious smooth. Installed cranks and gave them a spin. It's what every man, woman, and child wants.

I installed same BB (also new) in Gus and tightened to spec. When I turn the spindle by hand it is not smooth (definitely some resistance and a tad sticky) like the one I installed in Atlantis or an uninstalled one. Why is that? I checked it before install, and it was butter smooth. I uninstalled it from Gus, and it spins butter smooth. I reinstalled main body section to spec, and it is butter smooth, no change. When I install the opposing cup (Shimano calls it an adapter), at this point is when I begin to notice a notable change in spindle rotation smoothness.

I've ensured proper shell widths. And I've ensured shell/cartridge faces are clean and blemish-free.

Of note, opposing cup spins freely during install for about one third the way to full seat. From there it spins freely part of rotation and not freely otherwise. I can turn it by hand still using splined-tool, but there is definitely resistance during part of the rotation. After I can't go any further by hand, I fully seat with torque wrench.

Could it be that the threads on either side of the shell are not exactly coplanar, since threads are not continuous from one side of shell to the other?

It shouldn't be a shell facing issue, because the opposing cup doesn't interface with shell face.

Confounding to me. There isn't much to installing a new cartridge style BB into a new frame...screw it in. That's the problem, in part. There's nothing to correct with install technique. I'd love to be wrong and get it butter smooth like one in my Atlantis, for example.

Please, share your thoughts as to what the source of issue may be and recommended remedy!

Scott in (I want it to be spring, summer, and fall) Montana

[Scott Luly]

Edit correction to my post, please.

Second sentence of third paragraph of original post should read:

When I turn the spindle by hand it is not smooth (definitely some resistance and a tad sticky), unlike the one I installed in Atlantis or an uninstalled on.

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[JohnS]

Hello Scott,

Is there a screw for the under bottom bracket cable guide? It could be a tad long and interfering with the bottom bracket. I would recommend backing it out and if that helps adding a washer to the screw or replacing with a slightly shorter one. I've had some difficulties with bottom bracket installs in the past due to the cable guide screw being too long.

Hope it helps,

JohnS

[Mr. Ray]

Don't worry.  Your "new" UN91 bb's are likely over 15 years or older since leaving the Shimano factory.  The grease inside has probably changed viscosity due to non-use.  Cartridge bb's don't usually require a "ream and face" of the bb shell so if the cups are torqued to spec just attach cranks and ride.  The spindle should spin smoothly after breaking in.  My last UN91 wasn't torqued to spec and lasted over 30,000 miles.  I only tossed it because I tossed the frame and couldn't get the cups loose easily.    

On Sunday, January 15, 2023 at 1:52:56 PM UTC-5 Scott wrote:

[Garth]

I've notice this with both Shimano and Tange cartridges. If torqued to what the manual says, the spindle doesn't rotate freely. It's not "supposed" to do that, but what good is that when it does ? So, I lessened the torque. I also apply teflon tape on the threads, along with the grease. While teflon tape's "supposed" purpose is to prevent leaks and keep the threads from seizing, it also fills the gaps in the threads and acts like a mild thread locker. (I also applied some teflon tape on a Delta bathtub single scald-guard knob mounting bolt that wouldn't stay tight, not even locitite worked, at least the blue crap I had. The darn bolt on the cap hasn't budged with the tape.) I had one Shimano NDS cup that did slooowly loosen over a loooong time. So with that I removed the NDS cup, applied a little blue loctite with the tape and it hasn't moved since. When in doubt, just throw everything in there ......in other words ... what you need to do will come to you as needed.

The NDS cup with cartridges doesn't need to be that tight, it's only purpose is for mounting in the frame. As such, it doesn't matter how tight it is, unless it binds the bearing that is.

The cartridges that have a lipped NDS cup(UN54) were never an issue, only the newer ones without it. The UN72 was never a problem either.

That's the story of that .......

[George Schick]

Another thing that can be done, and I've done several times with both Shimano and Phil BB's that kept working loose, is get a locking ring from an old three-piece BB set, torque the NDS cup to where it feels right, hold it in place with the BB wrench and tighten down the locking ring on the few threads that remain visible outside of the BB shell with a locking ring wrench.  Loctite, Teflon tape, or whatever can also be applied on those threads before installing the locking ring.

[Nick Payne]

I always chase and face BB shell threads before installing a bottom bracket. Almost universally I find there is some misalignment and/or distortion that the taps and facing cutters correct. Even custom frames from well-known builders benefit from having this done.

Ditto for the reaming of the head tube and fork crown.

Nick

[ascpgh]

Your NOS BBs have really nice high quality bearings. I would imagine that the tolerances related to a mild load on those bearings that accumulate from the bearings themselves in the cylinder, the cartridge installation cups' receptacle ends, their threading and the frame's BB threading when all torqued to spec add up enough to produce some perceived interference to silk smooth finger rotation. 

BBs take a pretty big load in use and the bearings (of units that become legend like yours) are not particularly delicate but superior enough in precision that you can  feel some resistance prior to what break in will produce. They ought to be fine. 

When I replaced the Phil Wood BB in my Rambouillet with an SKF for a shorter spindle when going from triple to wide double I was stunned by the drag the SKF's seal system put on finger rotation and installed crank free rotation after spinning them. Not because of a single outer rubber grommet but the labyrinths of each end and lubricant inside. No grinding or destructive feeling load felt, I built enough box bikes to know how a cruddy BB feels by the intermittence of resistance or that grinding feeling in the 360° of rotation. By free tune up time after the sale some of the most mundane no-brand BBs were running smoothly and kept doing their job for a reasonable if not notable duration given how primitive and cheap they appeared to be.

Hubs act the same way to finger rotation or wheel free spinning after installation. I came to dislike Shimano Parallax architecture hubs because of their rubber cone seals, connected to axle nut, engaged and rotated in a large diameter but thin groove on the end of he hub body. Lots of drag on top of the tactile sense that they were easily overcome by dust, water or mud.

Andy Cheatham

Pittsbugrh

[Scott Luly]

Respondents, I'm grateful for all your input/suggestions. Once again, I've learned through your experiences.

John, read your suggestion about possibility of screw retaining BB cable guide being too long and interfering with BB and immediately grabbed my screw driver to check it. Unfortunately (or fortunately), that's not source of increased BB spindle rotation resistance I described in my original post. Given the location of screw in BB shell and shape of BB itself in same location, the screw does not touch the BB when fully seated. Great suggestion, though!

Mr. Ray, I think this model BB came onto the market beginning in the mid 90's, so it is likely as old as you note. If the grease viscosity changed over time, I think spindle spin resistance would feel same with BB uninstalled vs installed. However, I do buy into your suggestions "just attach cranks and ride" and "the spindle should spin smoothly after breaking in." Thanks for the reassuring "don't worry" advice.

Garth, my issue isn't bits coming loose. I'm going to stick with factory torque specs; and if something comes loose, I'll throw (or at least consider) the kitchen sink at it.

George, thanks for the tips about how to address loose bits.

Nick, a quick search on Google machine for pros/cons to chase and face of new frames reveals entrenched camps both for and against. Both camps make sound arguments, depending on the BB type and other factors. I'm going to avoid the DEEP rabbit hole my comments/thoughts for or against would take us. I welcome yours, though. For now, since my BB is a cartridge-type and threading-in DS and NDS by hand felt way smooth, I'm going to forgo chase and face steps.

Andy, I appreciate you sharing the personal metrics you've acquired having installed many BBs. It's that knowledge base I wanted to tap into. I'm inclined to agree with your comment "the [BB] bearings (of units that become legend like yours) are ... superior enough in precision that you can feel some resistance prior to what break in will produce. They ought to be fine." Regarding your sentence "No grinding or destructive feeling load felt, I built enough box bikes to know how a cruddy BB feels by the intermittence of resistance or that grinding feeling in the 360° of rotation," that's insightful. While I do feel an increased resistance to spinning the spindle by hand after the BB is installed, there is no "grinding or destructive feel" to the 360 spindle rotation, and it is perfectly smooth, just increased resistance.

While my wrenching skills are deft (IMHO), I lack the metrics one gains through voluminous installations of various bits. BUT, I'm not scared to ask those that do have experiences, so thanks, all!

Hope everyone's 2023 is off to a good start...

Scott

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