geneman
03-02-04, 02:22 PM
Ok, these are installed on triples but are they there to accomodate a larger cassette or because you need to take up slack from using a small chainring (like a 30)?
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Road Cycling - long cage derail.
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brokenrobot
03-02-04, 03:10 PM
Ok, these are installed on triples but are they there to accomodate a larger cassette or because you need to take up slack from using a small chainring (like a 30)?
-mark
Both? It's to account for a larger range. Either a small ring in the front with a normal-length chain or a bigger large cog in the rear with a correspondingly longer chain will result in more "droop" in some gear combination - the long cage is to take up that extra droop.
At least, that's what my novice logic sez ;)
-chris
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Both? It's to account for a larger range. Either a small ring in the front with a normal-length chain or a bigger large cog in the rear with a correspondingly longer chain will result in more "droop" in some gear combination - the long cage is to take up that extra droop.
At least, that's what my novice logic sez ;)
-chris
Stubacca
03-02-04, 03:31 PM
It effectively accomodates both, but mostly works out to be about the range of the crankset (particularly on a triple, where you shouldn't need the biggest cassette sprockets). Both a short- and a long-cage rear derailleur specify the same maximum sprocket size (at least for Shimano, all = 27T).
The longer cage allows for more chain slack to be catered for through a larger total capacity (total capacity = front range [biggest crank ring - smallest ring] - rear range [biggest sprocket - smallest sprocket]).
I've just asked a question in the mechanics forum to help confirm my understanding for a cassette change I want to make... :) From what I figured out, on a standard double (39/53) the short cage derailleur will work with all Shimano road cassettes (largest they make is Ultegra 12/27).
The longer cage allows for more chain slack to be catered for through a larger total capacity (total capacity = front range [biggest crank ring - smallest ring] - rear range [biggest sprocket - smallest sprocket]).
I've just asked a question in the mechanics forum to help confirm my understanding for a cassette change I want to make... :) From what I figured out, on a standard double (39/53) the short cage derailleur will work with all Shimano road cassettes (largest they make is Ultegra 12/27).