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Zippy · 05-09-2008, 04:55 PM

Long? Short? I know rear derailleurs come in various lengths, but why? Is one better than another? Are they designed for specific applications?

Definitive knowledge please, not: "It's not the size of the cage, but how you use it that counts..."

Thanks!

jeffj · 05-09-2008, 05:02 PM

Depends how much slack it has to take up due to the various chain lengths needed for various gear combinations.

A road bike two-chainring setup may get away with a short cage derailleur with a cassette that doesn't have a wide range.

Derailleurs usually state how much of a difference in range they can handle expressed in 'teeth'.

A long cage RD can handle something like a 42 tooth difference between 1x1 and 3x9 on a MTB. Add up the teeth on both extremes of the shifting range and see what the difference is.

On a MTB, it may be an advantage to use the shortest cage that works so the derailleur doesn't hang down as far and present itself to rocks and other snags.

davidB · 05-09-2008, 05:03 PM

good thread about this and most everything you'll want to know is in the 2nd post

lukewiens · 05-09-2008, 05:04 PM

i believe the longer the cage the better quality and more consistent shift you will get. shorter cages are beneficial in clearance situations or when you are bashin' through a bunch of rocks!

that's what i've been led to believe anyway!

check this...
http://www.beyondbikes.com/bb/tech/?section=rdr

now i know!

Zippy · 05-09-2008, 05:19 PM

Quote:

Originally Posted by davidB

good thread about this and most everything you'll want to know is in the 2nd post

Excellent answer. Thank you.

evdog · 05-09-2008, 07:04 PM

That is a great (technical) explanation. Practically speaking I have always understood that a short cage D would normally be used only on a 1x9 application, such as a DH bike, as there is less variation in chain length. On a 2x9 or 3x9 there is more variation, therefore you need the longer D to take up more slack. I guess thats the gist of what he says.

05-09-2008, 04:55 PM	#1 (permalink)
Zippy Small, but Mighty	Der Cage Length: What's it mean? Long? Short? I know rear derailleurs come in various lengths, but why? Is one better than another? Are they designed for specific applications? Definitive knowledge please, not: "It's not the size of the cage, but how you use it that counts..." Thanks! __________________ L8 APEKS: "Never underestimate the power of stupid people in large groups." Swim, bike, run. www.zippyathlete.blogspot.com

05-09-2008, 05:03 PM	#3 (permalink)
davidB Secret Squirrel Society	good thread about this and most everything you'll want to know is in the 2nd post __________________ "The Path is simply the best bike shop in Southern California." - Brewmaster www.thepathbikeshop.com

05-09-2008, 05:04 PM	#4 (permalink)
lukewiens Reformed Triathlete	i believe the longer the cage the better quality and more consistent shift you will get. shorter cages are beneficial in clearance situations or when you are bashin' through a bunch of rocks! that's what i've been led to believe anyway! check this... http://www.beyondbikes.com/bb/tech/?section=rdr now i know! __________________ "when you get hurt and all of your sacrifice adds up to nothing, are you willing to put it all on the line again?" - conrad stoltz MY BLOG - EMTB Quest for 24 hours solo Last edited by lukewiens; 05-09-2008 at 05:07 PM. Reason: added link

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05-09-2008, 05:02 PM	#2 (permalink)
jeffj Bloated Ogre	Depends how much slack it has to take up due to the various chain lengths needed for various gear combinations. A road bike two-chainring setup may get away with a short cage derailleur with a cassette that doesn't have a wide range. Derailleurs usually state how much of a difference in range they can handle expressed in 'teeth'. A long cage RD can handle something like a 42 tooth difference between 1x1 and 3x9 on a MTB. Add up the teeth on both extremes of the shifting range and see what the difference is. On a MTB, it may be an advantage to use the shortest cage that works so the derailleur doesn't hang down as far and present itself to rocks and other snags.

05-09-2008, 07:04 PM	#6 (permalink)
evdog Senior Member	That is a great (technical) explanation. Practically speaking I have always understood that a short cage D would normally be used only on a 1x9 application, such as a DH bike, as there is less variation in chain length. On a 2x9 or 3x9 there is more variation, therefore you need the longer D to take up more slack. I guess thats the gist of what he says.

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