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'clunk' at random times.

Old 09-23-08, 03:56 PM
  #1  
nahh
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'clunk' at random times.

I'm having trouble diagnosing a noise. Every once in a while, usually after coasting around a turn, i hear a faily loud 'clunk' as i begin pedaling again. It also happens when i'm out of the saddle going up a hill, but rarely.

It's not the bottle bracket, in my experience that's usually rythemic. It's just three or four times a ride, just enough for me to notice it.

any ideas?
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Old 09-23-08, 06:23 PM
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Caribou2001
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I'm just shooting in the dark here, and being a noob my nomenclature may be off but here goes anyway...

depending on the freewheel/cassette there are a certain number of locations the hub can "lock" when you start putting power to the pedals... is it possible that the clunk you describe is from the rotation before this "locking" giving the parts enough momentum to "clunk" when the locking engages?
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Old 09-23-08, 07:53 PM
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That might be it. I should've thought of that.
I'm just trying to make sure something wasn't seriously wrong, i try not to let stuff such as this go until there's a failure in a component.

thanks, happy riding.
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Old 09-24-08, 10:59 AM
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j mendivil
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Don't worry: A failure confirms diagnosis! happy riding to you too.
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Old 09-24-08, 11:28 AM
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Al1943
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Check for a tight link in the chain.
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Old 09-24-08, 12:35 PM
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or a worn or mis fitting power link
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Old 09-24-08, 03:18 PM
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i asume a deraillur equipt bike. try the frozen link thing or a stuck pully wheel on the deraillur. have experienced this problem more times than i care to admitt, thats why i mainly ride single speed or IGHs.
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Old 09-24-08, 05:14 PM
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Go through Sheldon's "creaks" article, it's good for helping diagnose them.

Since it sounds like it's usually under reasonably heavy load, I recommend greasing the stem bolts and the seatpost. That's gotten rid of similar creaks for me. Other than that, you could be looking at cranks, BB maybe?
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Old 09-24-08, 05:36 PM
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Originally Posted by nahh View Post
I'm having trouble diagnosing a noise. Every once in a while, usually after coasting around a turn, i hear a faily loud 'clunk' as i begin pedaling again. It also happens when i'm out of the saddle going up a hill, but rarely.

It's not the bottle bracket, in my experience that's usually rythemic. It's just three or four times a ride, just enough for me to notice it.

any ideas?
http://www.sheldonbrown.com/creaks.html
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Old 09-24-08, 05:54 PM
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I had a "clunk" that would appear and disappear, randomly, but seemed to be worse when putting the drive train under stress (like riding uphill). It turned out to be a worn-out freewheel. Tightening the bearing race ring helped, but I didn't get rid of the noise completely until I replaced the freewheel. If your bike has a freewheel, try wiggling it and see if the part of the body to which the cogs are attached wobbles a bit side-to-side around the center part.
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