When to Replace a Worn BB?

Thanks for your comments and opinions.

I'm interested in some actual results of the simple test I posted originally:

Note the play is not "lateral" but in the yaw axis.

Don't guestimate, measure it...


How much play in a cartridge BB is too much?

My friendly LBS tested mine today, and said it was "okay really", but when he tested it on the granny ring he conceded it might be better changed.

Waggling the cranks with your hands you can both see and feel play in the yaw axis.

I measured it with the chain on the granny, and the left crank parallel to the chain-stay; the pedal end tip of the left crank moves 1.0 mm from side to side as you waggle the cranks. (It is wear on the bearings btw, not loose cups.)

Is this tolerable or too much in your opinion?

Please try this test on your BB and post the result here.
(You may be surprised. Often there's more play than you might imagine.)
 
When I was working on the 96 Stumpjumper (UN52) this past winter, I noticed it had the kind of play you speak of. Wasn't really that measurable, but you could definitely feel it move. It wasn't a side to side movement, but more of an up and down type (which made the crank arm move in and out towards the chain stay).

When it starts moving so much that it's scraping the chain stay, I'll probably replace it. I figure if it took it this long to get less than a millimeter of play, it should take another thirteen years to have a full millimeter, right? :LOL:
 
Change it! It's not going to get any better is it? And now you've noticed it you'll always be aware of it!
 
GlassTrain":pwe4bzl7 said:
When I was working on the 96 Stumpjumper (UN52) this past winter, I noticed it had the kind of play you speak of. Wasn't really that measurable, but you could definitely feel it move. It wasn't a side to side movement, but more of an up and down type (which made the crank arm move in and out towards the chain stay).
When it starts moving so much that it's scraping the chain stay, I'll probably replace it. I figure if it took it this long to get less than a millimeter of play, it should take another thirteen years to have a full millimeter, right? :LOL:
I may be in a minority, but I support your principle of using things as long as you can. The notion of trashing anything that isn't perfect seems a strange one for a retrobiker.

On the other hand, I don't think your logic is necessarily correct. Once you can feel play in an assembly that should have no play, it's a sign that it's damaged. And once it's damaged, the rate at which it damages itself further in use will accelerate. So I'd guess thirteen years for the first mm and thirteen weeks for the second. And hopefully it'll send you some clear messages before it destroys your chainstay!
 
Maybe it is better replaced. It's not grinding or anything, but movement other than intended can't be good for it. I can't help but wonder if the plastic retaining cup hasn't hollowed out or something. Doesn't sound or feel like metal to metal, but more like metal to hard plastic.

Anyways... Thanks for bringing me back to my senses. :)

While I'm at it, I'm thinking about a new Dart 2 fork, v-brakes, and a new Mavic wheelset! :twisted:
 
Silverclaws asked:
"Well, in answer to the OP, if you are renewing the drive train, why not renew the BB as well. I have just done it on a '93 Saracen, one of the new UN54's, if it goes wonky, then I will replace it, it isn't exactly a hard or time consuming job. "

Simply because of the serious concerns about the quality of Shimano parts emanating from their Singapore factory.

eg: Quote from my LBS this week: (An honest, trusted, and proven Bloke who sells all makes.)

"Well we can certainly get you a Shimano UN54, or whatever you want, but even we cannot be sure of the quality. We just have to take what we get from them." He showed me a draw full of duff Shimano BBs and suggested I get a VP BB as they are "better than Shimano". And much cheaper too.

eg. Quote from another LBS when I picked up a pair of Genuine Shimano axle cones I ordered for another bike.

Me: "Are you sure these are genuine?"

LBS (looking sheepish): "Well... I'm sure they were made in the Shimano Singapore factory..."

Nuff sed!

Even buying a UN54 or UN73 from the UK doesn't ensure it wasn't made in Sg., as the English chap I mentioned before discovered to his cost. QC in the Japanese factory may have toppled too.

There are also many Chinese sellers on eBay hawking brand new Shimano parts from Sg and Tw factories, and of doubtful provenance. I understand they have huge back-doors.

The Trek MTB BB problem is long-standing, and well known over here, and at Trek HQ.

So I may be better sticking with a 17 year-old worn BB than a new Shimano one of poor quality.
It's not the cost, it's the hassle, and then the concern that your new BB will fail on a long touring trip. (I just completed a 1000 km tour on the old BB.)


Silverclaws wrote:
"I flushed it through and a load of orangey fluid came out..."

An indication it may be rogered, but the rust could have cultivated on a non-bearing surface not splattered with grease. An old known good-un may still be better than a brand new-but-dodgy one.

"...but if there is cause for concern, it is good to know and maybe if the big 'S' finds out we know, it may make them sort out their problems, as reputation is the most important thing in any company ..."

There's certainly cause for concern, but complaining to the factory in Sg or Shimano HQ in Japan would be a waste of time. It is so commonplace, they MUST already know and are simply trying to cover up, and oust the managers responsible without loss of face, spilling of trade secrets etc.

With the present cost-cutting fever forced on companies by the current collapse of Capitalism (hip hip Comrades!), the QC at Sg is not going to improve. Cost-cutting favours lower production time, fewer staff, and higher output, not longer time spent checking quality and proper hardening of materials.

Unless consumers make a loud noise, Shimano products will get worse not better.

Then there's the intriguing tensions of Chinese Singaporean sub-managers in the Sg factory, answering to Japanese owners. Totally different attitudes to work, business culture, and ethics. (Think baby milk-powder and Melamine. I know that was PRC, and Sg isn't Shanghai, but...)

Just a hop away are the Chinese Taiwanese bicycle parts manufacturers plotting to topple Shimano, and the Tw bicycle assembly plants trying to keep both sides happy. Would they like to influence the Chinese managers at Shimano Sg? Would those managers want to be "influenced".

Waiting by a Malaysian Chinese hotel reception desk I overheard the Proprietor turn away an enquiring Japanese tourist, "No rooms. Full!" (It was half-empty).

Noticing my raised eyebrows, the owner beckoned me into a courtyard at the rear of the building to show me the spot where, as a boy, he'd witnessed his relatives beheaded by the occupying Japanese forces.

Business is business... No? Not always.
 
Tallpaul with an expression like a stunned-mullet tapped out:
"How many people stand around talking about square taper BB's?"

Evidently plenty on the Retrobike forum, that's what it's for Chum.
But I prefer sitting for such serious matters.

Don't get me started on shovels and meat n'tater pies either...

Alright, since you press Sir...

There would have been no Industrial Revolution without both.
No railways, no canals, no Potato Famine, no telegraph system, no Internet ... and NO RetroBike Forum!
 
Anthony from sunny two-chimney-stacks Hove wrote:
"I've always been pleased with Shimano bbs, but maybe they all came from Japan and I didn't know that the Singapore factory had a bad reputation."

They appear to do more business out of their back-door, than a Knightsbridge knocking-shop. There are individuals who make their entire living shuttling around SE Asia with cases of dodgy bike parts from Singapore, often advertising them on eBay as "Genuine Shimano" parts. They tend to be the ones also flogging knock-off "Rolex" watches, "Fodak" cameras, and surprisingly inexpensive "Gucci" leather goods.
 
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