Short/Medium Cage Derailleurs?

[Greg]

I've heard recommendations to go with a shorter cage derailleur when I need to replace it. I guess the reason is obvious - less chance of it getting ripped off over rocky techy sections. Question is why do manufacturers usually default to a long cage? Is there a benefit to it? Is it only needed if you run with the biggest ring?

 

[Gremf]

I always understood it as a requirement for the number front rings and their sizes you are running. On my IH I have a long but really only need a medium because I am running a bash guard where my large ring used to be.

 

[bvibert]

AFAIK the longer cages are to give you enough chain to work on the big ring and bigger cassette cogs while still being able to take up the slack to work on the small ring and smaller cassette cogs.

 

[Highway Star]

Is that anything like a short to medium sized halfpipe?

 

[Marc]

AFAIK the longer cages are to give you enough chain to work on the big ring and bigger cassette cogs while still being able to take up the slack to work on the small ring and smaller cassette cogs.

Correct. If you're using a chain (generally speaking) on wide range of cog/ring sizes, you need a long cage to have capacity to take up the slack of using a chain that's really way to long on your smallest cog combo.

Remember the 'cage' is really just a chain idler. The more slack you have, the bigger the idler needs to be. The wider your range of cog sizes, the bigger the chain has to be, the more slack will be present on the smallest combo.

 

[eatskisleep]

I run a Shimano Deore SS Short Cage road derailleur on my mountain bike. Better than any other derailleur I've used on the bike.

 

[bvibert]

I run a Shimano Deore SS Short Cage road derailleur on my mountain bike. Better than any other derailleur I've used on the bike.

Do you only run 1 or 2 rings up front, or are you just really careful about gear combinations?

 

[eatskisleep]

I run two rings up front... I had no problems with two rings up front and 9 speed in the rear. Currently I run two rings up front and 5 cogs on the rear cassette, I dropped the gears I used least, it's a sweet setup and it gives me a really straight chain line too.