Substitute for Shimano UN26 BB?

Substitute for Shimano UN26 BB?

Postby Flo » Mon Nov 26, 2012 5:47 pm

Does anyone know of a decent substitute BB for the Shimano UN26 BB?

I have a Scott Sportster that has developed an irritating (and somewhat intermittent) click especially when under load and I'm almost certain that the BB is the culprit.

I'm loathe to put in another UN26 if there is a better/more reliable substitute..

Cheers.

Flo
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by BNA » Mon Nov 26, 2012 5:56 pm

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Re: Substitute for Shimano UN26 BB?

Postby il padrone » Mon Nov 26, 2012 5:56 pm

Get your LBS to check out and service the BB. I had one on my old bike (a UN-72) that had been working well for 15 years then developed a click. Took it to a bike shop in Adelaide, sure that a new BB was in order. They said we'll check it first. They pulled it out, cleaned and re-greased the BB thread.... and it was fine, clicking gone. That was two and a half years ago and the BB is still in service :D

If you do really need to replace it the next BB up (in square taper) is the UN-55. Or even better quality is the UN-73 which is still available. But be sure you get you measurements for it correct (marked on the BB cartridge usually).
Riding bikes in traffic - what seems dangerous is usually safe; what seems safe is often more dangerous.
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Re: Substitute for Shimano UN26 BB?

Postby Flo » Mon Nov 26, 2012 6:20 pm

Hi il padrone,

This BB hasn't had much use; probably less than 1000 kms over 4 years. I have been riding it more regularly in the last few weeks trying to build up some bike fitness before buying a road bike.

Do you know if your BB had come loose?
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Re: Substitute for Shimano UN26 BB?

Postby il padrone » Mon Nov 26, 2012 6:38 pm

Hi Flo

No. Corrosion in the thread is what can cause creaking or clicking. Removal, a dose of grease and refitting, was all that it needed.

Clicking could also be a loose crank - worth checking that they're tight.
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Re: Substitute for Shimano UN26 BB?

Postby Flo » Mon Nov 26, 2012 7:33 pm

Thanks for that il padrone. I'll check it out.
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Re: Substitute for Shimano UN26 BB?

Postby MattyK » Tue Nov 27, 2012 11:35 am

For the cost of replacement it's hardly worth repairing. UN54 and UN55 are the next models up.

FWIW I have that same BB, and it's been fine for years of commuting. I had an annoying squeak/creak, mostly under load like you describe, turned out to be a pedal.
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Re: Substitute for Shimano UN26 BB?

Postby rustychisel » Tue Nov 27, 2012 12:35 pm

as il Padrone explained, it's almost certainly the BB threads (water washes in grit and washes out grease) rather than the unit itself.
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Re: Substitute for Shimano UN26 BB?

Postby il padrone » Tue Nov 27, 2012 5:08 pm

Random or cyclical clicks and creaks can be the worst things to track down. Might be the BB.... or the crank-bolt.... or my EBB.... or the chain-ring bolts.... or the pedal.... or loose saddle rails.... or loose seat-post.... or.....

I've struck all of these at different times, with basically the same noise :|
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