Q: Campagnolo chain wrap and rear derailleur cage size

[telenick]

Does anybody know what rear derailleur cage size I'll need for a 34-50 11-23? This is for '07 Campagnolo.

My LBS guy says it's a medium. Perhaps the forum can confirm or deny.

Many thanks.

[Dave]

Campy used to claim that the short cage only had a 27T wrap capacity, but since they started making compact cranks, it's listed in the instructions as compatible with the 50/34 and up to a 13-26, which is a 29T wrap.

http://www.campagnolo.com/pdf/7225195_Rear_derailleur.pdf

The key to success is adjusting the chain length properly, so it will handle any cassette, except a 13-29.

Two tests will determine if the chain is the correct length. First, it must not hang loose in the little ring, little cog combination. If there is no tension on the chain in the little ring, little cog combination; remove two links (one inch) at a time, until there is. When the ends of the chain are brought together, some movement of the lower pulley should occur, indicating tension is being applied. Two more links (another inch) may need to be removed, beyond the point of absolute minimum tension, to keep the chain from rubbing on the chain guide tab as it passes under the upper derailleur pulley. If you want to see how much lower pulley movement will occur, without removing the extra inch of chain, shift up four teeth (11 to 15 or 12 to 16). This has the same effect as removing two links. Once this is done, the chain is set to the maximum useable length. Removing additional links will do nothing but reduce the derailleur's capacity.

Second, the chain must be long enough to avoid over-extending the rear derailleur when shifted to the big ring and biggest cog combination. If the chain is set to the maximum length as described, it should always pass this test, unless your setup exceeds the derailleur's stated wrap capacity. If you deliberately exceed the derailleur's capacity and the derailleur is over-extended in the big ring/largest cog combo, then you must either avoid that combo or add another inch and avoid using the little chainring and the smallest 3 or 4 cogs (since the chain will hang loose).

[telenick]

Did you just pop out of a phone booth, Dave?

Your response was faster than a speeding bullet.

Thank you.

[marcus]

I run a 53/39 and a 13/29 with a short cage, cause that's what I had available. This is a 30 tooth wrap, which is right at the limit of what is possible. Your combo requires a 28 tooth wrap, so a short cage will work.

[djcwardog]

...on a 2007 Campy Centaur short-cage RD. It seems to work fine: extra movement possible with the RD in the big/big combo - not that I ride that, just want to avoid putting the RD into the spokes if I hit that combo by accident!

BTW - also running a 53/39/30 external BB triple, and a long-cage DA RD with an IRD 11-28 (Shimano setup) cassette on my other bike - and it works fine also.

The key is to adjust chain length on the initial install. Get the chain as long as you can in the little/little combo as written about above - then check it for big/big before you cut the chain. My Campy instructions call for a 10-15mm vertical height of the chain over the lower pulley... a bit confusing by their illustration but you get the idea...

[ERDR]

i run that exact setup with a standard (short) derailleur. absolutely do not need the mid size. btw, that is a perfect range, nearly a straight block with plenty on both ends for nearly all conditions. enjoy.
s.