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PostPosted: Wed Apr 10, 2013 2:01 pm 
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I'm after some advice on this one, its starting to drive me a bit NUTS!

52/42 Chainrings. 6 speed freewheel, largest cog is 24. 1979 Campagnolo Nuovo Record RD. Sedis Chain used but not much.

I spent an hour watching and adjusting this last night but basically it seems fine on the 42 ring through 1-2 gears and its ok through 4-5-6. But it skips on 3.
Seems ok on the 52 ring through 7-8 and 10-11-12, but skips on 9, the same sprocket.

If I watch it closely, as the chain moves through the lower cage, at certain points I can see it tensioning the cage slightly (1 or 2mm), then the tension releases and the cage springs forwards. This seems to cause the skip on the sprocket. Its not easy to see every time but the chain hits the top of the teeth of the sprocket instead of engaging.

The gear cable is new and not slack but firm with the lever forwards. The chain was fitted around the 52 ring and the 24 sprocket plus one link. I've tried altering the chain tension by moving the wheel to the front and back of the dropouts which made no difference. There are no stiff links in the chain.

The jockey wheels do have wear, possibly they are causing the problem although both jockey wheels move freely.

I've been thinking about this at work all day :roll: I'm kind of drawn back to the chain and I do have a spare so can swap it as a process of elimination.

There's not much to adjust on these derailleurs, but am I missing something?


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PostPosted: Wed Apr 10, 2013 6:20 pm 
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:facepalm: Its the 4th sprocket not the 3rd.

I've just been having another look.

When its on the 4th sprocket, if I wind the crank backwards, after only 5/6" of the chain moving through, the chain links become out of line to the sprocket teeth so the chain starts riding up on top of the teeth.

I'd think of a worn chain, but its ok on the other sprockets.


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PostPosted: Wed Apr 10, 2013 6:34 pm 
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I'd put money on it being a slightly stiff link.


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PostPosted: Wed Apr 10, 2013 8:15 pm 
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Sounds like a stiff link except that it should skip on the other cogs too. Have you tried replacing that cog with a new one?


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PostPosted: Wed Apr 10, 2013 8:16 pm 
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Featch wrote:
I'd put money on it being a slightly stiff link.


How much have you put on? :)

I've taken the chain off and measured it, 12 links are exactly 12" so zero wear. Thought I'd try turning it over just out of curiosity and it did exactly the same thing.

Now I've put on a new chain and its perfect :?

I can't find a stiff link but I'm pretty sure it can't be anything else.


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PostPosted: Wed Apr 10, 2013 8:19 pm 
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American Friend wrote:
Sounds like a stiff link except that it should skip on the other cogs too. Have you tried replacing that cog with a new one?


I seem to have sorted it with a new chain. Bit of an odd one though, I can't find a stiff link and it only did it on the one sprocket. Although, generally, its a lot smoother with the new chain.

I thought Sedis were the Rolls Royce of chains! Replaced it with a KMC.

Kind of bugs me though that even when its fixed that I can't be sure what was wrong!!


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PostPosted: Wed Apr 10, 2013 8:27 pm 
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Out of curiousity, did you break the chain recently? I mean split it, not literally break it.


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PostPosted: Wed Apr 10, 2013 9:33 pm 
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American Friend wrote:
Out of curiousity, did you break the chain recently? I mean split it, not literally break it.


Yes, it had been split and its the type where you have to use a chain splitter to wind out the rivet, although the link went back together ok and was free moving.


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PostPosted: Wed Apr 10, 2013 11:12 pm 
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I'd put money on the link you joined is the stiff link. :lol:
chain's fine. just bend it a few times back and forth at the link you joined to loosen it.

BTW, I was laughing because this happens to everyone. If you put the chain back on the bike, join it together again, and slowly turn the cranks backwards, the place where the chain hops slightly is the stiff link. You can loosen it by bending the chain as above or with a decent chain tool. A decent chain tool has be two places for the chain, an outer and an inner; the inner allows you to move the pin without moving the face plate. The best way to avoid this kind of nuisance is to join the chain with a master link. :)


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PostPosted: Thu Apr 11, 2013 2:56 pm 
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Joined: Tue Oct 09, 2007 1:55 pm
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I'd bet it's a worn cog. It's no coincidence that it only does it on one sprocket.


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