Campaign rear der / chain length question

[djdj]

I have a 2006 10 pd. record rear der, with a 50/34 crank. Running 11/23 and a new Campag chain. I've set up the chain length per Campag instructions (small-small, with ~1cm distance between bottom of der cage and chain when in the 11/34). However, in the 12/34, there is less distance -- in fact, the chain is rubbing the bottom of the cage. Thoughts? :confused:

All of the shifting is smooth and noise-less, except in the 12/34.

[oldpotatoe]

I have a 2006 10 pd. record rear der, with a 50/34 crank. Running 11/23 and a new Campag chain. I've set up the chain length per Campag instructions (small-small, with ~1cm distance between bottom of der cage and chain when in the 11/34). However, in the 12/34, there is less distance -- in fact, the chain is rubbing the bottom of the cage. Thoughts? :confused:

All of the shifting is smooth and noise-less, except in the 12/34.

Not possible. Going to a 1tooth larger cog and the chain gets droopier? Is it coming off the lower pulley? Back cage on backwards/upside down?

[djdj]

Yes, droopier. If you say impossible, I would believe it, except I'm seeing it.

Cage on correctly, per manual, and the chain is staying on the pulley.

[Ralph]

Agree with OP....don't understand your description. Is the chain rubbing on the edge of 50 ring as it crosses over to smallest cog in rear?

[oldpotatoe]

Yes, droopier. If you say impossible, I would believe it, except I'm seeing it.

Cage on correctly, per manual, and the chain is staying on the pulley.

Is the 12t cog bigger than the 11t?

[djdj]

Sorry for being unclear. It is rubbing the pulley/cage guide tab on the rear der. See the attached photos. The top photo is 12/34, the bottom photo is 11/34.

1697927564

[djdj]

Spud, checked that also. The 12 has a larger diameter than the 11.

[oldpotatoe]

Spud, checked that also. The 12 has a larger diameter than the 11.

Beats me.....?

[Hindmost]

Chain too long? In the 34 11 the chain looks slack. In the 34 12 the chain tightens and rubs the derailleur. Maybe?

[parallelfish]

I am going to guess that the chain is overly long, with no tension on the rear cage. The clearance is the result of the untensioned chain drooping. Going to the twelve cog takes up just enough slack to create some tension in the system, and the resulting interference.

[carpediemracing]

Is there some play in the derailleur such that cable tension causes the derailleur to tighten up and in the process move up?

Hm I need to be in front of a bike and fiddle a bit to see what it might be.

[lhuerta]

Chain too long? In the 34 11 the chain looks slack. In the 34 12 the chain tightens and rubs the derailleur. Maybe?

THIS...


I am going to guess that the chain is overly long, with no tension on the rear cage. The clearance is the result of the untensioned chain drooping. Going to the twelve cog takes up just enough slack to create some tension in the system, and the resulting interference.

...and THIS

[thwart]

As long as you're going to mess a bit further with it... get a newer ultra narrow chain while you're at it. Shifts a bit better and is quieter, at least IME.

You can pick up a Veloce version for $30 or less.

[parallelfish]

It is simple. Look at it from the other perspective. If it is too long on the 12, it is too long on the 11.

The chain is too long.

[AngryScientist]

i always size my chains big-big. do that and shorten the chain so the RD is stretched out to almost max there and i bet your problems are solved.

[ultraman6970]

U sure it is a 12T cog?

[carpediemracing]

Sorry for being unclear. It is rubbing the pulley/cage guide tab on the rear der. See the attached photos. The top photo is 12/34, the bottom photo is 11/34.

1697927564

The lower photo, in the 11, clearly shows the chain sagging. You'll need to shorten the chain a bit.

You can also screw in the B screw or whatever the one is called that does the same thing but is on the lower body. However that will pull the pulley down from the cogs so you'll reduce shifting accuracy across the range. Best to shorten the chain.

I'm guessing two pairs of links. You want to be 1 link shorter, at least, than what you have in the 12. Add 2 links because you're not even on the 11 yet. Based on installing chains on my bikes I usually end up shortening one pair past when you have in the 12, which means taking a pair out on top of a pair.

Therefore I'm guessing two pairs of links.

This would give you the long version of "proper chain length", which I follow. If you go minimum chain length in big-big + one pair of links, aka Shimano, you'll probably need to shorten 3 pairs, maybe 4 pairs of links.

[djdj]

Thanks all for the advice. This is an Ultra-narrow chain. I originally had the chain one link shorter, which was outside the clearance that Campag recommends in the small-small. I was also getting a lot of chain drop at that length. It seems there is no Goldilocks length with this frame.

[thwart]

This is an Ultra-narrow chain.

My apologies... Campy must have changed their graphics recently. That C10 labeling was used for their earlier generation of 10 spd chains... which were 6.1 mm instead of 5.9 mm, IIRC.

Good luck with your chain length issues. Worse case scenario (that is, until you can get someone with Campy expertise like Old Spud to actually lay eyes on it), the problem only occurs when you're in 11/34 or 12/34, so that sounds like something you can work around... 'should' avoid cross-chaining anyway.