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Annoying Noise
#1
Evening

Canvassing opinions on an annoying noise.

The bike is a Ribble R872, high modulus carbon frame, 105 groupo.

I get a rattle/buzz only when in the large chainring and only in the third and fourth largest sprockets. It's high pitched, almost like a vibration. Shift up or down the cassette from these sprockets, no noise. Small chainring, no noise.

I'm pretty capable in terms of set up, I can strip down and rebuild a drivetrain fairly competently so the obvious tweaks in relation to indexing and general set up I don't think are applicable. In fact I have started from scratch and set everything up and the noise is still there. The bike is new, within the first 2000km, I didn't hear it at first, I'm fairly sure it's come on in the last couple hundred km.

Chain isn't rubbing on the front derailleur and it's not a symptom of cross-chaining as when I shift up the noise goes.

Tightened all the chain ring bolts, crank arms, headset, pretty much anything that can be tightened has been carefully tightened.

It's got internal cable routing, not sure if that is anything to do with it.

The gears shift perfectly so it's not a performance thing but the noise is in the sweet spot, so it's there a lot.

At a bit of a loss really...any ideas?

Tom
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#2
Try to push/pull/twist the cable housing that runs thru the frame when this is happening and see if that makes a change. (carefully without crashing)
also try it in a trainer and see if this happens, the bike has less vibrations in a trainer. just one way to cross check a vibe issue
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
  Reply
#3
Pure guesses:
- the cassette has a tiny amount of play in those gears. Make sure it is tight, assembled properly
- pulley wheels, these could be sensitive to chain angle and wobble a little at certain times. Try oiling them to see if it changes
- internal cable vibrating against frame. I could see that high or low shifter cable tension might hold it so it doesn't vibrate, while "just right" tension puts the cable in a position to rattle against the frame.
  Reply
#4
(04-06-2014, 01:27 PM)Steadinski Wrote:  Evening

Canvassing opinions on an annoying noise.

The bike is a Ribble R872, high modulus carbon frame, 105 groupo.

I get a rattle/buzz only when in the large chainring and only in the third and fourth largest sprockets. It's high pitched, almost like a vibration. Shift up or down the cassette from these sprockets, no noise. Small chainring, no noise.

I'm pretty capable in terms of set up, I can strip down and rebuild a drivetrain fairly competently so the obvious tweaks in relation to indexing and general set up I don't think are applicable. In fact I have started from scratch and set everything up and the noise is still there. The bike is new, within the first 2000km, I didn't hear it at first, I'm fairly sure it's come on in the last couple hundred km.

Chain isn't rubbing on the front derailleur and it's not a symptom of cross-chaining as when I shift up the noise goes.

Tightened all the chain ring bolts, crank arms, headset, pretty much anything that can be tightened has been carefully tightened.

It's got internal cable routing, not sure if that is anything to do with it.

The gears shift perfectly so it's not a performance thing but the noise is in the sweet spot, so it's there a lot.

At a bit of a loss really...any ideas?

Tom
Unlikely to be related in any way to chain angle, including pulleys, front derailleur rub, etc, as it occurs in middle cogs. Also unlikely to be related to freehub for the same reason.

Please *measure chain wear* (Google if you don't know how) and let us know the results, as well as if you ride those cogs far more often or less often than the ones that do not make noise.
  Reply


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