Touring - Capacity Question

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voshchev
09-05-07, 04:03 PM
So, I would like to move to a Shimano Ultegra 9spd short cage derailler, but I'm not sure about the capacity. The derailler has a 29 teeth capacity. On my bike I'm running a super compact double (46-30) and a 12-27 cassette, thus--if I'm calculating correctly--I need a RD with a 31 teeth capacity. So, the question is whether I can use an ultegra short cage (they look SOOO much better than long cage models) with this set up?

seeker333
09-05-07, 07:20 PM
sounds like you need long cage


http://bike.shimano.com/catalog/cycle/products/component.jsp?PRODUCT%3C%3Eprd_id=845524441770437&FOLDER%3C%3Efolder_id=2534374302053476&ASSORTMENT%3C%3East_id=1408474395181785&bmUID=1189041855186
brucewiley
09-05-07, 07:23 PM
Hmmm, I believe the 29 tooth capacity you refer to for the rear derailleur means the maximum cog size on the wheel end of the drivetrain. In otherwords you'll be fine with a 12-27 & short cage. On my road bike, I use a short cage (with 50-34 on front) and it's good up to 27 teeth on the cogset I think. Long cage would be more appropriate for a triple.

On the touring bike I use a 44-32-22 though with a 12-30 rear, hey, I'm old and need the advantage.

Bruce

seeker333
09-05-07, 08:36 PM
capacity for rd = (big ring-little ring)+(big cog-little cog).

the rd cage has to take up all the slack chain, whether it comes from rings or cogs.

in addition shimano normally specifies a min and max cog size.