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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 01-21-14, 08:20 AM   #1
buhodiaz
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cable guide bolt mark on bottom bracket shell

Hello,

My name is David, i'm from Chile (southamerica). I got a mechanical question.
I bought a Trek 7.2FX three months ago, having been riding about 600km (mostly commuting), I began to listen a noise from the crankset. The first thing I made was pay attention to all another posibility causes. I mean: pedals, Front derailleur, chain, tightens, etc. I didn't found anything. Then I disassembled the crankset and took off the bottom bracket. The noise source was indeed the BB.

First question: It's possible that a new BB (3 month) fail as soon? Is it associated to the washing procedure?

When I took off the bottom bracket I saw that the cable guide was touching the BB. Is it normal?

By the way, sorry about my poor english, I hope you can understand




thanks in advance

David
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Old 01-21-14, 08:43 AM   #2
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David, Does the bottom bracket's main body rotate independently of both cups (parts that screw into the frame)?

You can use a washer or two to space the cable guide's screw further away from the BB cartridge.

Brad
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Old 01-21-14, 08:56 AM   #3
buhodiaz
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David, Does the bottom bracket's main body rotate independently of both cups (parts that screw into the frame)?

You can use a washer or two to space the cable guide's screw further away from the BB cartridge.

Brad

The BB just rotates independently from one cup. The other side is fixed (chainrings side).

I planned to use a washer for the cable guide screw.
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Old 01-21-14, 09:01 AM   #4
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With a BB unit this young I'd suspect that it was moving within the shell under power. We see this frequently. But try spinning the axle and see how it feels. If the axle spins smoothly and has some "lube resistance" then I'd reinstall it. Coat the shell's insides with grease as well as the BB's outsides. Remove the BB cable guide's bolt and washer it as already mentioned. Reinstall the BB and secure it pretty tight. Again do the axle spin test. If the spin has tightened up and gotten rough you do need to replace the BB, if still smooth then continue. Put the rest back together (don't forget to double check the ft der adjustment) and go for a ride. Retorque the crank arms after a few miles. I expect that you'll find the noise gone. Andy.
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Old 01-21-14, 09:10 AM   #5
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You could also grind the end of the bolt shorter. Don't forget to properly torque the BB after reinstalling it.
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Old 01-21-14, 09:48 AM   #6
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Sadly, I think the axle does not spin smoothly enough. To be sure, I will replace the BB but I will take care about all you have advised me. Maybe it was caused by an assemble failure (no grease, wrong torque...).

Thank you very much for all your answers.
Regards

David
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Old 01-21-14, 10:06 AM   #7
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Another modern type bottom bracket failure - I am surprised - I know of two other sealed bottom bracket failures on mountain bike types - Better check your crank as well...

Is it still true that loose balls rule...
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Old 01-21-14, 11:46 AM   #8
buhodiaz
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Another modern type bottom bracket failure - I am surprised - I know of two other sealed bottom bracket failures on mountain bike types - Better check your crank as well...

Is it still true that loose balls rule...
Can I ask: What do you mean with 'Better check your crank as well...'?
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Old 01-21-14, 11:52 AM   #9
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a washer under the screw head on the out side , will make that screw penetrate
that much less on the inside..
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Old 01-21-14, 12:23 PM   #10
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I strongly doubt that the bolt had anything to do with the bottom bracket's failure, which was most likely weather or dirt related. The bearings are well outboard of the damaged center section who's sole purpose is as a spacer between the two bearings.

That said, thread the bolt back into the open BB shell, and gauge how far in it extends, then file or grind it shorter, so it just enters the shell the slightest bit (or buy a shorter bolt).
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Old 01-21-14, 12:32 PM   #11
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Yea, I only saw scrapes on the sleeve , which matters nothing to the bearings them selves..


Just buy another cartridge BB, and go on with your life ..
more important things to concern your self over, are coming ..
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Old 01-22-14, 11:36 AM   #12
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Quote:
Originally Posted by buhodiaz View Post
What do you mean with 'Better check your crank as well...'?
Seems the sealed bottom brackets are well made - So what would cause one to fail - I think maybe lateral movement compressing the ball retainer rings (with reservations my assumption) - If the retainer rings were buggered then the spindle might bind - In another words a great deal of force, a bump, a fall, deforming the bottom bracket itself - This much force could cause the crank or crank arms to bend as well???

All I am saying is that bottom brackets are pretty tough stuff and anything that could cause one to fail could have done other things to your bike - Better check it all out just to be safe...
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Old 01-22-14, 11:44 AM   #13
buhodiaz
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Quote:
Originally Posted by zandoval View Post
Seems the sealed bottom brackets are well made - So what would cause one to fail - I think maybe lateral movement compressing the ball retainer rings (with reservations my assumption) - If the retainer rings were buggered then the spindle might bind - In another words a great deal of force, a bump, a fall, deforming the bottom bracket itself - This much force could cause the crank or crank arms to bend as well???

All I am saying is that bottom brackets are pretty tough stuff and anything that could cause one to fail could have done other things to your bike - Better check it all out just to be safe...
thank you for your answer zandoval. (And sorry about my little understanding )

I installed a new BB last night and everything went back to normal. But I'm seriously thinking of change my crankset to a DEORE M591 (currently I got a M131 junk).

Regards

David
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