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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 07-12-04, 09:08 PM   #1
operator
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Crank Noise

This is on a mountainbike, has a cheapy cup and cone bottom bracket. What happens is when pedalling (especially on the smaller rings) there is a popping noise when the right crank arm passes through the 11'oclock position. The crankarms/pedals are not hitting the frame and the front cog is also not hitting anything on the frame.

It becomes less pronounced as you shift higher and is undetectable under force (say under acceleration) in high gear. It is very evident when pedalling lightly in low gear. Take it in for service? Or is there something I am overlooking? I don't have the tools right now to take apart the bottom bracket at the moment.
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Old 07-13-04, 03:08 PM   #2
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When you get the tools, have a look at the bottom bracket and see if you can find anything.
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Old 07-14-04, 01:17 PM   #3
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Try looking for a bent tooth on the chainring, as the severity seems to be affected by chain alignment.
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Old 07-14-04, 01:43 PM   #4
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I kind of doubt it's a bottom bracket problem.

Since it happens at the same place in the pedal stroke, I'd take a hard look at the crank. As Andrew mentioned, a bent chainring tooth seems a likely possibility. Another is your crankarm may be hitting the front derailleur.
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Old 07-14-04, 02:56 PM   #5
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This fixed almost every noise on a bike:

1) Take out your seatpost.
2) Clean seatpost.
3) Grease the seatpost.
4) Reinstall seatpost.
5) Ride and listen.

(I know this because Tyler knows this.)
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Old 07-14-04, 04:02 PM   #6
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Rofl, okay. So what happened was while inspecting the BB, noticed my lockring was slightly loose. I'm guessing it was moving around under power (?). Anyways, tightented it, no more knocking/popping feel.

Thanks for all the help!
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Old 07-17-04, 09:39 PM   #7
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Well that may have been premature, the noise is back and worse than ever. It only occurs on all gear combinations.

The small gear rings produce nicely defined clicking/popping noises while the high gears produce a squeaking noise.

I also noticed the squeaking noise only happens when pedalling on the right pedal and only in the 12 o'clock to 6'oclock range. The bike is still under warranty.

Should I bother investigating further or just get it exchanged.
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Old 07-17-04, 10:01 PM   #8
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It's starting to sound like maybe loose chainring bolts. Still, why wonder? If it's on warranty, I doubt they'll exchange it, but they'll fix it.
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Old 07-17-04, 10:21 PM   #9
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Looks like i'll need to pickup a chainring screwdriver :/
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Old 07-18-04, 07:10 PM   #10
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What should I grease the seatpost with? Chain lube (tri-flow) okay? or WD-40 or will I have to buy some type of grease...
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Old 07-19-04, 09:37 AM   #11
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Quote:
Originally Posted by operator
What should I grease the seatpost with? Chain lube (tri-flow) okay? or WD-40 or will I have to buy some type of grease...
Buy some kind of grease. I like Phil Wood, but since this use involves no bearings or anything, you can get away with supercheap white lithium grease from the hardware store if you have some...

-chris
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Old 07-19-04, 11:15 AM   #12
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If your BB lockring was loose enough that you could turn it by hand, then it's likely that the bearing adjustment is now off. Can you feel play in the BB by hand?
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Old 07-19-04, 01:37 PM   #13
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Ok, this is really starting to annoy me. It must be lubrication problem somewhere. I rode out today with the annoying squeak again, halfway through it started drizzling and miraculously the noise disappeared. I know I lube my chain enough, and I just did my seatpost (which did nothing, but now the quickrelease really does quick release ).

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If your BB lockring was loose enough that you could turn it by hand, then it's likely that the bearing adjustment is now off. Can you feel play in the BB by hand?
I couldn't find any webpages detailing this? Is there anything I should be looking for? I just tightened it until it seemed reasonable.
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