rm -rf

I replied to a PM about my use of a 13-29 with a short cage derailleur. This isn't supposed to work, but it often does work OK. So I'm posting the info on this old thread, too.

Here's the question to me:

Hi,

I've got a 13-29 Campy cassette, never mounted, and am looking at mounting it on a setup very similar to yours: 50-34 compact chainset, short throw derailleur, and the 13-29 cassette.


Some questions, if you don't mind:

Did you make up a chain specifically for this setup? If so, how long was/is it?

Approximately how long are your chainstays?

Did you make any adjustments to your rear derailleur?

Are there any other tips or ideas you can share?

Thanks in advance.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Fitting a 13-29

I just used my existing chain. I had a 13-26 before.

The 13-29 is "supposed" to be too big to work with the short throw derailleur, but a lot of riders had success with it. Actually, I don't remember anybody posting that the 13-29 didn't work for them.

Fit isn't necessarily related to chainstay length, I don't think. Probably the chain stay length and the angle of the dropout all work together.

Just swap the cassette and use your existing chain. I have a bike stand, so I could shift to the big chainring-big 29 cog and see if the chain was long enough for the big-big combination, and also not too long for the small-small combo.

Go to the big chainring, then carefully shift up to the 29 cog.

In the big-big combo, my derailleur still isn't stretched out flat. It still has a small angle to take up the slack. The top derailleur pulley doesn't hit the 29 cog. It's very close though. I adjusted the "B screw", the rack and pinion adjustment at the base of the top pulley, counterclockwise to have a little less tension on the cage rotation, to lower the top pulley slightly. Edit--that didn't shift very well--I moved it back to the middle of it's range--much better.

In the small-small combo, the derailleur is almost folded back all the way. But there's still tension on the chain, and the chain doesn't touch the top pulley again as it passes out of the bottom pulley. (Even it if did touch, it would still work reasonably well--I unkowningly rode it that way when the bike was new with a 12-25, because the LBS left the chain a little too long.)

I this is actually the reason the 13-29 isn't recommended by Campagnolo, because on some bikes, the short cage might not be able to take up the slack on the small-small.

If the chain is too short for the big-big, you'll need to extend it. That's tricky to do correctly, maybe you have the leftover chain from when it was cut to fit. Make sure you use the replacement pins that come with a new chain. Never re-use a pushed out pin.

If it's too long, you'll need to shorten it. But before shortening, kind of hold it by hand with a couple of links pulled together in your fingers, and see if that looks correct. Remember, you always have to remove an outside and an inside link, making the chain 1 inch shorter.

You might want to use this quick link, Wipperman Connex 10 speed narrow. These work great, and you don't have to be technical with the pin install. The quick link replaces one of the outside links, and connects to two inside links.