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Broken rear derailleur

Posted: Sat Mar 24, 2012 9:30 am
by owl
Hi there

My campag rear derailleur is playing up. When I move the chain into the inner chain ring, the rear derailleur does not seem to be taking up the slack. As a result the chain is slapping the chainstay. At first I thought my chain length was too long, I trimmed the chain by 2 links which has made no difference. Hence I think it is the rear derailleur. Has anyone come across this before?

Thanks

owl

Broken rear derailleur

Posted: Sat Mar 24, 2012 9:30 am
by Weenie

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Re: Broken rear derailleur

Posted: Sat Mar 24, 2012 10:56 am
by theremery
try moving the jockey wheel cage. Does it have spring tension remaining?

Re: Broken rear derailleur

Posted: Sat Mar 24, 2012 3:12 pm
by owl
Thanks - yes there is plenty of spring in it comes back with real force - could it be chain length still. In 53/25 it looks plenty tight

Thanks

owl

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 3:25 am
by stella-azzurra
Whats' 53/25? :noidea: Hopefully not your front chain rings.

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 4:01 am
by timzcat
53/25 I am sure is big big.

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 4:58 am
by rambotan
stella-azzurra wrote:Whats' 53/25? :noidea: Hopefully not your front chain rings.


53T Front and 25T Rear

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 6:45 am
by alexalecu
Adjust the b-screw.

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 8:23 am
by owl
thanks for that I will loosen the b screw, to pull the cage further away

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 1:14 pm
by BobSantini
If your freehub is binding for some reason (freewheel bearing seizing or broken pawl in the gubbins or cogs touching spokes or ....) then the chain slack will occur at the top of the chain as you describe whenever you stop pedaling.

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 1:21 pm
by bikerjulio
chain slap is obviously more likely when in the small ring since the chain is much closer.

here's a pic of a big-big combo with the RD extended as far as you'd want to go

Image

and in the small-small

Image

Re: Broken rear derailleur

Posted: Sun Mar 25, 2012 2:53 pm
by owl
Thanks for all the advice. The answer - bobsantini you were the correct. Over the winter I put a miche primato cassette on for my turbo, put about 600 miles on it on the turbo and took off a recon cassette which I put on for 2 short rides at the end of last season. The miche primato cassette is slightly too wide causing it to seize the freehub when freewheeling when the cranks are at 11/4 o'clock if that makes sense (what a crock of shi@!).

I swapped cassettes and chain - problem solved. Wont sell my recon cassette now :wink:

Re: Broken rear derailleur

Posted: Mon Mar 26, 2012 1:24 pm
by Geoff
That B-screw needs to be adjusted...

Re: Broken rear derailleur

Posted: Mon Mar 26, 2012 1:24 pm
by Weenie

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