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Thread: Cage Length

  1. #1
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    Cage Length

    How do I know what size rear derailleur cage I need? What does chain wrap refer to?

  2. #2
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    You need to pick the rear derailleur cage length based off of what capacity you need. Capacity refers to the sum of the range of teeth on the cassette and the range of teeth on the crank. IF you have a 11-34 casette, the range is 23 teeth and for a crank with 22-32-44 gearing the range is 22 teeth. The total capacity required for this set-up would be 45. If you use a rear derailleur with too low of a capacity, it will not be able to take up the slack or provide adequate chain tension in some gear combos. If you use a 3x9 set-up, you need a long cage (SGS) rear derailleur, if you use a 2x9 set-up, you can use a medium cage (GS) rear derailleur.
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  3. #3
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    Quote Originally Posted by seachicken11
    How do I know what size rear derailleur cage I need? What does chain wrap refer to?
    You need a long cage if you are running a triple ring crank. If you run double ring up front a medium cage works nice. I have a 2X9 with medium cage XTR on my trail bike which works well.
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  4. #4
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    Thanks Guys....

    Thanks it all makes sense now.

  5. #5
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    Ooosp, gues I made a Boo BO then Right now I'm running a MEDIUM cage XT RD using a tripple crankset and 11-32 casette. Real fact of the matter is that most bikes using tripple ring cranksets come with the long cage for all those people who don't know what's considered bad gear combos, if you use the correct gear combos the medium cage is even fine (can be a bit on the close side) for a 11-34 cassette and tripple cranks.

    Good gear combos.... granny ring and no higher than 5 cog(could push 6 in a pinch), middle ring and 2-8 on cassette (can in a push go to 1 or 9) Big ring and now lower than 4 on cassette (in a pinch u could go 3). I have my chain length set up so that in BIg Ring and 4 cog tha cage is pointed straight to the ground/vertical (with my 11-32 cassette on) and it works fine with both my 11-32 and 12-25 cassettes.

    I switched ot the medium cage to try to use a shorter chain and hence get ride of chain slap and it has worked very well for me so far - don't hear that damn chain slapping all over my chainstay now when I'm bombing down rough stuff, gear combo also plays a part in this.
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  6. #6
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    A medium cage will generally just be barely enough to handle up to a 32t cassette on a triple standard crankset of conventional spread such as a 22-32-44 while still keeping tension on all gear combos and allowing for 44-34 crossover. This is an oversimplification as there are other factors but it should give you an idea of what to expect. Long cage is pretty much the one size fits all of rear derailleurs.

  7. #7
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    When you size your chain, if you size it so it is just long enough to wrap around the big cog and big chainring combo instead of adding the extra two links, this will work with a medium cage derailleur. This does provide you with better shifting and less chain slap.

    However, if the rider is in the large cog and accidently shifts into the large chainring instead of the small chainring, it could result in frame damage. This is why Shimano does not recommend doing this.
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