Can I use the same chain length for 2 derailleurs?

on-yer-bike

I use an 11-25 Campag cassette and may want to change it to 13-29 for the Marmotte.

I'm also in the process of upgrading my Centaur to 09 carbon and so will be buying a new rear mech.

I know I need to change to a medium cage rear derailleur. Can I use the same length chain whilst I'm using the 11-25 with the med cage derailleur? As I'm not definite about the Marmotte I don't want to have to change my new KMC £45 chain until nearer the time. I think I would with an 11-23 cassette.

Are there any disadvantages with using a med cage derailleur full time instead of a short cage?

Mister W

The optimum chain length is determined by the size of the chainrings and cassette, not the length of the rear mech.

I can't see any problem with running a medium cage mech all the time. It will just move a little less than a short cage mech.

rickhotrod

If a short mech will clear the 29 sprocket you could just run a short cage mech.

Assuming 50/34 chainrings are used, and a range of sprockets from 11 to 29...make sure the chain is long enough to go round the short mech when on the largest chainring and sprocket ie. the 50 and 29. Assuming the short mech can cope with a combined front and rear teeth difference of 29, you can go down to the 16 sprocket when on the small chainring. If you want to run a smaller sprocket when on the small chainring, fit a medium mech.

John.T

A medium cage mech will need a longer chain as there is a longer run between the cassette and the bottom jockey. Probably no more than 1 link. No reason not to run a medium mech. They look fine and would handle all the combinations that you mention without any changes. Set your chain length for the largest ring/sprocket combination and it will handle anything smaller with no trouble.