I have a 2008 Chorus rear derailleur and since few days it's making an annoying friction sound when the chain is on the big chainring (53) and smallest cog (25). At first I thought it was the chain that was rubbing against the derailleur hanger but it's not the case. Is the cage bent ? Can't figure out what's wrong. I didn't touch the b-screw.

Photo:

Do you mean the big chainring and the smallest sprocket? Smallest sprocket will be an 11 or 12, and 25 your biggest.

1/ The aluminium hanger that the rear mech connects to is designed to bend if you crash or if your bike topples over. These often bend inwards towards the back wheel, and your shifting stops working properly.

2/ Or maybe your freehub has come loose and when the chain is on the smallest sprocket the chain is rubbing against the aluminium derailleur hanger. So, if you remove the wheel and pull on your set of sprockets a little, you might see what I mean. You only need pull a little. In order for the freehub to be tightened onto the hub you will have to remove the sprockets.

3/ Or your shifting is just out. Have you damaged the cabling to the rear mech?

Yes, I mean the 11 sprocket (smallest).

I can't replicate the problem on my repair stand. It's only happening while riding.

I have removed the cassette and re-installed it. I still have the same "rubbing" noise.

I didn't bent the derailleur hanger or damaged the cabling. It's shifting perfectly.

This is getting really strange and annoying

Thanks again

The chain could be rubbing against the inner portion of the front derailleur cage

Look at the orientation of the rear der cage against the large chainring in the background......some of that might have to do with camera angle effects.....but I'd start there with the chance that the der hanger is not what it's suppose to be......could it be getting loose, maybe starting to fail (if it's a cervelo then it will fail anytime or anywhere....Ha). Even if it's canted like that I wouldn't think it would give you rub noise as much as you'd get different shifting/noise issues when in the small front chainring versus the large....which you've said you're not getting.

Bottom line is I'd still have the hanger checked for alignment anyways.

Those 10 speed carbon rear derailleurs tend to be a copy of the 9 speed ones with the main change being the addition of carbon side plates.

My old Record 10 developed a lot of slop around the pin/plate interface which affected the parallelogram action. I don't know if the carbon ate into the pins or the pins wore into the carbon. The whole thing developed a kind of twist over time, and accuracy at the extremes of travel was affected. I don't know how hard you ride, but after 5 or more years, a system overhaul is possibly due.

The 11 speed rears are totally re engineered with relatively larger side plates which wrap around the pivot knuckles (giving more torsional stiffness) and have bushed pins. A Record (you can keep it Chorus) 11 speed rear derailleur cleaned up my shifting considerably, and works very well with 10 speed shifters and cassette.

Interesting, I have exactly the same problem but with Record 11 at the moment.

It's a brand new rear mech, new cables. I came a cropper and damaged my old mech. My new mech cage looks like yours (cage leaning in). Seems to shift well in the smallest gears (large sprockets) getting worse and noiser towards the smaller sprockets with the 12 being poor.

I'll have another go at taking of all the tension and rechecking limit screws tonight, otherwise it's to the LBS for hanger check tomorrow.

I did tweak the B-Screw to follow recommendations of cage approx 7mm from largest sprocket, didn't seem to do anything gap or otherwise.

@TimW
Definitely get your hanger checked. A mates new frame which was supposedly checked suffered exactly the same symptoms when in the 14, 13 & 12. Hanger just needed a little tweak.

@585 - Cheers , much better now.

I was wondering what do you mean by the "hanger needing a little tweak" ?

I still haven't found the source of my problem. Could be the derailleur hanger but it looks straight to me.

Thanks

Visual check of hanger is pointless....you need to use an actual tool (Park DAG-1) and have the hanger properly aligned. If you don't own the tool take it to a reputable LBS and have them check it. Once the hanger is aligned then readjust your b-screw. Good luck. EM3

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My 2013 Cervelo R5

agreed. cannot tell by looking.

after many years, I bought the alignment tool. was surprised at how many hangers needed significant adjustment.

_________________
There's sometimes a buggy.
How many drivers does a buggy have?

One.

So let's just say I'm drivin' this buggy...
and if you fix your attitude you can ride along with me.

http://www.youtube.com/watch?v=GekiIMh4ZkM

Same thing on my Athena rear derailleur.

I will have the hanger checked tomorrow. But I think my problem is the cage. Not only is it pointing inwards (vertically) like in the example above, It is also off by a flew degrees in the direction of the chain. Meaning that the lower jockey/pulley wheel is not being fed the chain straight.

The frame worked flawless with Sram Force derailleur. Switched to Campagnolo and this happened.