derailleurs cage size?

[mr_dove]

rear derailleurs come with medium cage or long cage.

What the heck does that mean? and does it matter? Will it affect the fit on the bike or it's functionality?

[rfemurfx]

no it does not effect the fit nor its functionality. o.k. well it kinda effects how the whole drive train works.

the only reason there are now two types of cages is to serve one purpose. YOU. depending on the gear combination you are running, both front and rear you will only have one choice. either long or short. if you look close at the rear der. cage you will see a couple of numbers stamped on it. one says Max. and the other says Total.

Max.-32t... that means the largest gear that der. can handle is a 32t cog. (cassettte)
Total-32t... that means that the total tooth difference between the front chianrings and cassette is 32 teeth. to figure that out simply subtract the largest chain ring from the smallest chainring then do the same on your cassette, add the two numbers together and Whoop There it is!!!

if you run a short cage der. when your numbers say to run a long cage, what happens is that the cage can not take up the slack of the chain when in the smaller gear combos and shifting may not be so hot.
THAT's IT!!

[GrahamKracker]

For most 3-chainring mountain applications, you will only ever use the long cage version. DH'ers and people running 2-ring setups can use the short cage, anyone else will suffer lessened shifting performance.