[RBW] Question on cartridge BB

[Andrew Johnson]

I am working over the new 66cm Quickbeam, and saw the cranks were flopping, which turned out to be from a loose BB. It's a sealed cartridge Shimano unit, had been installed by Riv. I guess the rings came loose, and the previous owner hadn't noticed.

BUT... the left side ring is plastic, is that normal? And, it's split/cracked across the threads... is that normal? Or a sign of wear and fatigue from the floppiness?

- Andrew, Berkeley

[Joe Bernard]

Some Shimano BBs have a plastic cup. They actually work just fine for many miles, but stomping on a loose one will crack it. You either need a nice/new/affordable no-plastic replacement from Rivendell, or this is your excuse to buy a fancy schmantzy Phil. Because you can adjust chainline. Which is vital on a singlespeed. That's my story, and I'm sticking to it..

 

Joe "trust me..I know what I'm doing" Bernard

Fairfield, CA.

[Garth]

Yes, you likely have a UN54 BB in there ... and it has a plastic cup.  The reason they usually break is people overtighten them. The need not be torqued as the misguided instructions say! Just snug is fine. But hey, plastic is just a bad idea period, for anything in the BB.. and Shimano's use of it is inexcusable.

You can get a new plastic cup, but you may be wondering if it will crack too... not really fun.  Another option is a new aluminum cup by Problem solvers called an Up-Cup #54. But, for the cost of the Up-Cup($15-20), you'd be better of just getting a new BB. Shimano now has UN-55's which use a steel cup, but I'd get a Tange LN-3922 from Tange. It's the same internals as the one Riv sells but is all steel.  The Tange's do not have that silly lip on the cup that the UN55/54's do, therefore allowing more chainline adjustments than with the Shimano. A second choice would be the IRD steel cup BB, easier to find.  I've gotten the Tange's from bike shops via ebay and online.

[Minh]

Andrew,

I'd say the UN54 is not really work saving with an UP-Cup, since
decent replacement tange bbs are not that expensive. I'd say buy a
replacement UN54 plastic cup ($3) and sell that BB on ebay or save it
for another bike.

[dougP]

While I agree that steel is a better material for the cup, I replaced
the original BB on my Atlantis with a UN-54 with the plastic cup. A
couple of years ago I noticed it had developed a crack. The crack
does not seem to effect anything so I've not bothered doing anything
about it.

dougP

[Philip Williamson]

I cracked the plastic left BB cup on my Quickbeam a couple weeks ago
trying to get rid of a creak. Yes, overtightening it. After 7 years of
perfectly serviceable plastic cup life, so the service life seems
acceptable to me.
Yesterday I took the cup out, greased it up and put it back, crack and
all. Creak appears gone.

Philip

Philip Williamson
www.biketinker.com

[Jim Thill - Hiawatha Cyclery]

The above commenters are correct that the plastic cup actually works pretty well, even when cracked. The plastic cups are the source of much hand-wringing (despite being functionally just fine), which I suspect led to Shimano changing to the metal cup on the newer model (according to a previous commenter).

Don't waste money on a Phil BB. IME, the Phil bearings don't last any longer than the Shimano cartridge, and they cost more to replace. In other words, your initial $150 investment doesn't translate to savings down the road.

[William]

<sarcasm>

That's not a crack, that's a "self-triggered strain relief".

</sarcasm>

[Seth Vidal]

I've found my problems with bottom brackets loosening up or with
cracking the plastic cups have vanished since I got a torque wrench
for my birthday the year before last. I love that thing.

-sv

[Allan in Portland]

My plastic cup was cracked on install by my neighborhood bike shop (in Portland, we have those in lieu of LBS ;-). Right on top, which somewhat annoyed me, as an otherwise out-of-sight, out-of-mind type of guy.

I figured if it mattered, I'd take it back, but they are super nice guys so I'd give them the benefit of the doubt that it didn't matter. That was, I dunno, 5 years ago? Never seemed to matter.

Regards,
-Allan

[Andrew Johnson]

I'm going to watch mine for a few weeks, and see if any slop or play develops. It is tight (torqued) on the right side, and the left side, though cracked) is serving to hold the spindle centered in the BB. I'll put some out of the saddle stomping on it, and see how it fares.

It just seems a terrible choice by Shimano to use a material that is so weak in an area that takes such high stress.

- Andrew, Berkeley

[Peter Morgano]

Isn't the UN54 only like 20 bucks?  I would think that even with labor at the lbs you are taking 40 bucks max. Seems like small potatoes for something that lasts for 5 years...

--
You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group.
To post to this group, send email to rbw-owne...@googlegroups.com.
To unsubscribe from this group, send email to rbw-owners-bun...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.

[dougP]

Peter:

You are correct on both points. High mileage riders and / or tough
conditions may shorten the life to a couple of years. That's why I
can't get too excited about SKF or Phil's.

dougP

On Oct 31, 10:40 am, Peter Morgano <uscpeter11...@gmail.com> wrote:
> Isn't the UN54 only like 20 bucks?  I would think that even with labor at
> the lbs you are taking 40 bucks max. Seems like small potatoes for
> something that lasts for 5 years...

> On Oct 31, 2011 1:31 PM, "Philip Williamson" <philip.william...@gmail.com>

> >http://groups.google.com/group/rbw-owners-bunch?hl=en.- Hide quoted text -
>
> - Show quoted text -

[stevef]

Steel cup'd Tange bottom brackets are available here, if you decide to go that route.  I've used them--they're good.

http://www.benscycle.net/index.php?main_page=advanced_search_result&search_in_description=0&keyword=tange+bottom+bracket

[Mark R.]

I got one of those, smooth out of the box, felt like a box of rocks
after a year and maybe 6k miles, I don't think the seals were good.
Maybe just mine, dunno. I have un shimanos that are smooth for well
over ten years of hard use.
Yep.

Mark
Howtostretch

On Nov 3, 5:58 am, stevef <stl...@gmail.com> wrote:
> Steel cup'd Tange bottom brackets are available here, if you decide to go
> that route.  I've used them--they're good.
>

> http://www.benscycle.net/index.php?main_page=advanced_search_result&s...

[Rex Kerr]

Adding another voice to the "ride it cracked" crowd.  I've installed, ridden, and otherwise abused BBs with a crack all of the way across the threads, and they worked fine for as long as the BB lasted.  Moreover, I once ground most of the threads off the drive side of a cartridge BB because the frame wasn't threaded all of the way into the shell, and no shops have french threaded BB taps anymore.

--

[Andrew Johnson]

Overdue update: I swapped out the old Shimano UN40 BB (68x113) for a new UN54 68x107 today. I gained a steel leftside cup, and a much better chainline on the Quickbeam. Back in early November, when I found the old cracked cup, I just put in a new plastic cup. It promptly cracked upon install, but at least stayed tight. I was preprared to live with it, until I got to checking my chainline and realized the 113 bottom bracket was unnecessarily wide. While looking for the Tange unit Garth mentioned, I found a Shimano at the LBS, along with some thin chainring spacers to help me nudge the chain over.

I brought the chainline down from 50+ mm in the front to just 45 mm, pretty close to the 42 mm at the rear. I could get it closer with thicker chainring spacers, but dem photos in RR41 scared me (page 16), so I'll ride with a 3mm offset between front and back for now. Maybe I can find a quality front ring with a lateral offset at the teeth?

Funny thing, RBW's website says all Rivs can use a 107 BB, and no question about it, the Sugino XD cranks fit very nice and close with the 107 unit. Hey, I just gained some pedal strike clearance! But it came assembled from Riv with the UN40 113 unit.

- Andrew, Berkeley

[dougP]

"Funny thing, RBW's website says all Rivs can use a 107 BB, and no
question
about it, the Sugino XD cranks fit very nice and close with the 107
unit.
Hey, I just gained some pedal strike clearance! But it came assembled
from
Riv with the UN40 113 unit.

- Andrew, Berkeley"

That's an interesting statement, considering that elsewhere Riv states
that BB selection depends on the frame and crankset. There used to be
a chart of BBs by frame but I can't find it on the new site. From
personal experience, a 110mm Shimano UN54 with a Sugino triple has
about 1mm clearance on a 58cm Atlantis. It would seem logical that
the frames that can take wider tires (Atlantis, Hunq, etc) need a
wider BB than say a Roadeo. I recall the chart listed 107mm for the
Atlantis & my thinking it must be a typo.

dougP

> > via ebay and online.- Hide quoted text -

[Andrew Johnson]

Here's the link to the cartridge BB page that references the 107mm BB for all Rivendells in combination with the XD2 crank:

http://www.rivbike.com/product-p/bbc.htm

I realized later, that the QB probably came with a wider BB in order to get its inner ring out from the chainstay. I'm running a single ring, in the middle position, and with these Sugino XD2 cranks, the chainline at from is 45mm, with about 9mm clearance betweeen the 40T chainring and chainstay. That works fine for me, and it would bring the granny gear pretty pretty close... but probably clearance for a smaller ring.

- Andrew, Berkeley