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Hey Folks,

Let me fill you in on my setup. I have a triple front derauler, which has just been tuned to try and remove the problem. I have the chain on the front middle ring and the outermost rear cog.

I get a mystery noise from the front rings that sounds a lot like a chain hitting the front derauler at a rhythmic pace. However, It is not hitting the front derauler in any way. I can manually control the front derauler via cable and center it on the chain and the noise is still there. The height of the derauler is also ok with no possibble chain or ring interaction.

When I pedal it up to speed and add a slight inner sideways pressure to the UPPER section of the chain, the noise then goes away. It also goes away in the middle gears of the rear sprocket. It seems somehow, that the chain/ring interface point on the top of the ring is actually causing this.

And this prblem manifested itself quickly. One minute, no noise, the next minute, it was making it.

Any suggestions?

THANKS!!!
 

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Sounds like your chain is rubbing ever so slightly on the large ring. You may not even see this when you look for it, but slight flexing from pedaling can increase it. Usually switching to the second "most outter" cog in the rear eliminates the noise.

It is something that you see sometimes on brand new bikes, even when they're set up with the right BB/crank combo. It's a tight clearance on a perfect setup. It is also a common problem that people suddenly notice one day. This is a problem that often does not show up when the bike is in the work stand.

It could be something as simple as a dirty chain that makes you suddenly hear the rubbing. You may have also bent the chain ring slightly, which would also expain a sudden occurance of the noise, another possibility is that your crank seated itself further onto the BB axle. On some campy BBs, if the BB cup on the opposite side of the bike loosens the actual axle and bearings can shift slightly over, but you'd usually feel looseness in that case.

Check you have the right size BB, depending on your setup you might be able to get a longer axle size. Another solution is to put a tiny spacer on the right side BB cup, knocking the whole crank out a tad. Trek OCLV bikes often come with a nifty little disc installed on the BB cup that's designed to keep a derailled chain from scratching up the carbon, it also serves well as a spacer for this type of problem.

Or just don't use that gear, you can train yourself to use others.

hope that helps
 

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naranjito
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785 Posts
exactly. if you cross chain, especially on a triple, it´s very likely (almost certain!) that the chain will catch on the big ring. by the time you´re on the outermost sprocket while on the middle ring, you could have changed up to the big ring and found an equal gear ratio but without cross chaining and without the chain catching on the ring.
 

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Arrogant roadie.....
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4,232 Posts
I'm betting you have a bent tooth.

BTW, a driveshaft is a long metal cylinder. It looks nothing like a chain, and 99.999% of bikes don't have one.
 

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Kant phuckin sphell
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650 Posts
I thought you

hikndarron said:
Hey Folks,

Let me fill you in on my setup. I have a triple front derauler, which has just been tuned to try and remove the problem. I have the chain on the front middle ring and the outermost rear cog.

I get a mystery noise from the front rings that sounds a lot like a chain hitting the front derauler at a rhythmic pace. However, It is not hitting the front derauler in any way. I can manually control the front derauler via cable and center it on the chain and the noise is still there. The height of the derauler is also ok with no possibble chain or ring interaction.

When I pedal it up to speed and add a slight inner sideways pressure to the UPPER section of the chain, the noise then goes away. It also goes away in the middle gears of the rear sprocket. It seems somehow, that the chain/ring interface point on the top of the ring is actually causing this.

And this prblem manifested itself quickly. One minute, no noise, the next minute, it was making it.

Any suggestions?

THANKS!!!
Had a BMW motorcycle for a second there....

I agree with b.g , It is the chain on the underside under less tension rubbing the large ring, dont lose sleep over it. Normal.
 
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