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  1. #1
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    When to use a Long Cage vs Short Cage Derailleur?

    I have a new SRAM X9 long cage derailleur, and another X9 that I now realize is "not long". Both are brand new, but the short one is ~16mm shorter.

    What is the proper application for long versus short cage derailleur? Will the short one work with a 11/34 cassette? Does it matter if the bike has a rear suspension or is a hardtail?

    Is my shorter X9 a "short" cage or "medium" cage? Thanks //kct

  2. #2
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    You've got a medium cage. Sram makes a short cage mountain derailleur in the X.0 line, but only goes as low as a medium in the X.9.

    <u>Quick answer</u>: The medium cage will work, but you'll drop your chain if you accidentally shift to the small-small combo. Suspension *could* be a factor, depending on how much "chainstay growth" your frame experiences as your suspension cycles.

    <u>Long answer</u>:

    Derailleurs have a rated capacity. This is their ability to take up excess chain. After all, you need just about all of your chain to run in the big-big combo, whereas you have a bunch of extra links doing nothing when you run in your small-small combo.

    Not that either of those cross-chain combos are normal to run in, but let me get to that in a minute.

    Manufacturer stated derailleur capacities are as follows:
    Shimano long = 45T; medium = 33T
    SRAM long = 43T; medium = 37T; short = 30T

    Speaking from experience, Shimano is a bit conservative in their capacity rating. I can only assume the same is true of SRAM (I'll get to that, too).

    The easy capacity formula is to add your big ring & cog sizes, then subtract your small ring and cog sizes. It looks like this:

    <b><i>cap req'd (T) = (BIG ring - small ring) + (BIG cog - small cog) </i></b>

    ...so for a typical 44-32-22 mountain crank & 11-34 cassette...

    <b><i>T = (44T - 22T) + (34T - 11T)
    .. = (22T) + (23T)
    .. = 45T</i></b>

    Using this simple forumla, you would need a derailleur with a 45T rated capacity to absorb all the possible extra links of a typical 27-speed drivetrain.

    (I make the assumption SRAM stated capacity is conservative, since they list 43T as the long cage capacity -- 2T short of what is required by this forumla).

    Where do shorter cage lengths come into play? Right here!

    Even though the long cage will, in theory, take you down to the 22x11 gear combo and hold adequate chain tension, let's be logical: 22x11 is a combo you don't use!

    Rather than use the generic formula, let's map out the capacity for each gear combination (based off of a Shimano cog pattern; SRAM will be slightly different):

    <img src="http://www.booboodog.net/images/derailleur-capacity.gif">

    44x34 starts off at zero because in that combo, all of the chain is being used up by the ring and cog, and the derailleur needs to take up none of it. As you shift through the cassette range (moving down the column), the amount of free chain increases as the cog size decreases.

    Take a look at the useable gears, which I've outlined in green and yellow. Those fall near the stated capacity of the medium cage derailleurs. (I mentioned that Shimano's stated capacity is conservative, and in practice, I find their medium cage to be closer to 39T.)

    For instance, in the middle ring (32) and the small cog (11), the table shows you've got to absorb 35T. This is near the stated capacity of either of the <b>medium cage</b> derailleurs. This gear combo remains useable, but you'd be better off shifting to your big ring for better chain tension.

    You can also see that to use a SRAM <b>short cage</b> derailleur (30T capacity) on this drivetrain would leave you with <u>two or three <b>un</b>usable gears</u> while in the middle ring, and only about three <u>useable</u> gears from your granny ring. (Any number greater than 30T on the table would be near the limits of the short cage derailleur.)

    Oops! Accidentally shifted into the unusable "red zone"? Nothing major: the derailleur cage folds back on itself, the chain droops, and you maybe drop the chain if you don't catch it in time.

    In my opinion, it'd be stupid to size a chain any smaller than what is required to shift into big-big. If you accidentally force a shift into that combo, which is certainly possible when you're tired or "in the moment", you don't want to break anything. <b>So chain length will be the same no matter what derailleur you choose.</b>

    <img src="http://www.booboodog.net/images/chainlength.jpg">

    Benefits of a shorter cage length?
    - snappier shifts
    - better chain tension
    - less chain slap / greatly decreased drivetrain noise (!)
    - better obstruction clearance / improved spoke clearance.
    - slight weight loss -- but you gotta be a real weight weenie to appreciate this one.
    Last edited by Speedub.Nate; 07-02-2006 at 11:23 AM.
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  3. #3
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    As a fyi

    Sram's X9 in short cage (not available to the public though yet ... pre production)
    Attached Images Attached Images

  4. #4
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    Thanks to Speedub.Nate for an outstanding explanation! Comprehensive and well written.
    //kct

  5. #5
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    I second that.

    Nate, you totally explained something that had mystified me. Very, very nicely done!

  6. #6
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    Nate!

    I'm sitting here thinking of the same choice in XTR derailleurs. Amazingly clear, concise and helpful.
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  7. #7
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    How would I calculate it if I run a single 38 in the front and a 11x32 in the rear? What size derailleur would I need? I'm interested in buying a Shimano Saint for my Specialized P.2 but I'm having trouble deciding what size I should get.
    Last edited by InnovateorDie; 10-30-2006 at 03:05 PM.

  8. #8
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    That's an easy one... go as short as you can possibly go.

    See, it's not the *size* of the front chainring that factors in, but the *range* between the biggest ring and the smallest ring.

    With an 11-32 in the rear, you've got a 21T spread, well within the capacity range of Shimano's short cage derailleur.

    (The capacity requirement for the front rings is Zero on your setup because it doesn't change at all.)
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  9. #9
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    I also found this info useful some time ago -

    http://www.beyondbikes.com/bb/tech/?section=rdr
    Last edited by energetix; 10-30-2006 at 06:41 PM.
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  10. #10
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    One of the most impressive responses I've seen on these boards. Great work speedub.nate!
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  11. #11
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    one more question...

    Great explanation..but whats the diff between "rapid rise" and "non rapid rise"? thanx in advance....






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  12. #12
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    "Rapid Rise" is Shimano's trademarked name for what is otherwise known as a <i>low-normal</i> derailleur. This means spring tension pulls the chain in/up the cassette to the lowest gear, and cable action pulls it out/down to the high (small) cog.

    The reverse of this is <i>high normal</i>, where the thumb press / cable pull drags the chain up the cassette towards the lowest (biggest) cog.
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  13. #13
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    thanx!

    great info..I love these forums!
    "I won't sell these for a penny less than $60.00. I'd rather put 'em back on the shelf and keep 'em! "

  14. #14
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    Speeddub.Nate - wow that explained so much

    Thanks
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  15. #15
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    med cage

    I'm finding my SRAM XO med cage works great with 11-34 cog. In fact it can accommodate the extreme large-large gear combo, but as we all know, it's not recommended with full-susp bikes (chain growth upon compression). The shifts are definitely snappy, quick and precise- partly due to the shorter cage, and mostly to SRAM's shift system.
    Question to a custom frame builder..."So what makes your bikes climb better?"....his answer, "Uh, your legs?"

  16. #16
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    Quote Originally Posted by HTail
    I'm finding my SRAM XO med cage works great with 11-34 cog. In fact it can accommodate the extreme large-large gear combo, but as we all know, it's not recommended with full-susp bikes (chain growth upon compression). The shifts are definitely snappy, quick and precise- partly due to the shorter cage, and mostly to SRAM's shift system.
    That, and my lasting impression during my first ride after switching to a medium cage on my 1x9 (32/11-34) was how remarkably quite my bike had become.
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  17. #17
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    Quote Originally Posted by HTail
    The shifts are definitely snappy, quick and precise- partly due to the shorter cage, and mostly to SRAM's shift system.
    Oh, so that's why my new SRAM X9 (long cage) doesn't feel as snappy as my old XTR medium cage. Also more chain slap and noise. I wondered if the medium cage X9 would handle the 34-11 rear cog with a normal triple chain ring... and apparently it will.

    Thanks.
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  18. #18
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    Again, med cage should be fine as long as you're conscious about your gear combos and follow the chain length guide measuring- large chainring to large cog + 2 links.
    Question to a custom frame builder..."So what makes your bikes climb better?"....his answer, "Uh, your legs?"

  19. #19
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    Smile

    Another big thanks to Speedub.Nate!!!

    Its been nearly 7 months, and his outstanding tutoral still goes VERY much appreciated

  20. #20
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    Thanks for great info~

    wow, it's great explanation nate. I think I have to dig these forums in,,

  21. #21
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    Thanks Man!

    Holy Cow. Speedub.nate awesome posts. Getting ready to replace my rear Derailleurs on one of my FS bikes. Still remember when I owned my Iron Horse HP how helpful you were to all of us in that forum. Thanks man for this post! This should be a sticky.

  22. #22
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    medium cage derailleur with bashguard

    thanks for the great info. I just replaced my big ring with a bashguard (and shortened my chain accordingly). The middle ring is still 32t, and my cassette is 11-34. so it seems to me, since i need to replace my bent (xtr - goddammit) derailleur, i could go with a shimano medium cage der. My bike is a heckler / 5.6" travel. Is this correct?

  23. #23
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    With that answer, I believe that Speedhub.Nate could really be....

    Time's "Man of the Year"

    Very nice. I know it's old, but that don't change it. It also saved me from making a jackhammer out of myself with what would have been my pathetic answer.


  24. #24
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    awsome thread, i always thought the longer the derail cage the better but maybe a med cage would work better for a 22-32 F, 11-34 R setup

  25. #25
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    I have an older RD-M951 XTR that's seen better days. Not quite sure of its cage length, but looks to be 2.75 inches between pulleys, short maybe? So w/ my current setup of an 8 speed 28-11 cassette and a 3 ring 44-32-22 giving me a capacity of 39...a Shimano RD-M960-GS needs to find a home on my Jamis, eh?

    It's interesting going around LBS and seeing a bunch of long cage setup stock. Guess they don't wanna see folks breakin' stuff.

    Thanks so much for your explanation Speeddub.Nate. I even managed to create my own little "good gear" pic.


  26. #26
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    I'm trying to figure out how having a single 34t chainring in the front would affect this.

    For example I have a 34t chainring in the front, and 11-34 in the rear. As far as I can use your formula I'm getting:

    (34-0)+(34-11)=34+23=57T

    Seems to work fine with a short cage though.

    Great sounding explanation but it's so late it's going over my head!

  27. #27
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    short cage is fine

    dropadrop-
    actually your setup requires a derailleur with only a 23 tooth capacity. when you run a sinle chainring, the difference up front is zero because you're not shifting up there, (the way to think about it is: biggest ring you are running - smallest ring, and your single ring is considered to be both of these, so its 34-34 = 0) and the formula reduces to the difference between the top & bottom cogs, which is 23.

  28. #28
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    What an excellent thread. I learned a ton reading through it. I am a relatively new rider and trying figure out mechanically why a shorter cage would offer better tension and smoother shifting if the chain stayed the same length. Is it based on lever mechanics? Tension on the end of the longer cage is less due to the mechanical advantage?

  29. #29
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    Quote Originally Posted by Bartj
    ...why a shorter cage would offer better tension and smoother shifting if the chain stayed the same length. Is it based on lever mechanics? Tension on the end of the longer cage is less due to the mechanical advantage?
    Right! Think of the cage as a lever arm. As you know, a longer lever is easier to displace against a fixed counter force.

    In this case, the fixed force is the tension spring, which is same spring regardless of which cage length it is installed on.

    The bouncing chain is attempting to operate the lever arm (derailleur cage) and displace the spring. Longer cage = easier to move. Shorter cage = more difficult.
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  30. #30
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    I would assume that if I'm reading correctly that a 11-32 with a 22-32-44 front would work great although I might have to watch the lower cogs in the back when in the 22?

    Thanks!

  31. #31
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    Quote Originally Posted by Speedub.Nate

    Oops! Accidentally shifted into the unusable "red zone"? Nothing major: the derailleur cage folds back on itself, the chain droops, and you maybe drop the chain if you don't catch it in time.

    In my opinion, it'd be stupid to size a chain any smaller than what is required to shift into big-big. If you accidentally force a shift into that combo, which is certainly possible when you're tired or "in the moment", you don't want to break anything. <b>So chain length will be the same no matter what derailleur you choose.</b>
    I see that the debate "long cage vs medium cage" is centered on the risk of destroying the derailleur if the chain is crossed in the big ring/big cog combo.
    In my opinion this is not correct.
    If the chain lenght is right, the only gear combos to avoid are the small ring/small cog - and the result of a wrong combination would be slack chain, and not a stripped derailleur.
    So the medium cage can be used without any risk even with a typical 22-32-44 crankset and 11-34 cassette, assuming that the chain lenght is correct.
    What is your opinion on this?
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  32. #32
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    Quote Originally Posted by Juanmoretime
    I would assume that if I'm reading correctly that a 11-32 with a 22-32-44 front would work great although I might have to watch the lower cogs in the back when in the 22?

    Thanks!
    According to my post above, this is correct.
    Hope that other opinions will follow.

    fab
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  33. #33
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    Quote Originally Posted by Ausable
    I see that the debate "long cage vs medium cage" is centered on the risk of destroying the derailleur if the chain is crossed in the big ring/big cog combo.
    In my opinion this is not correct.
    You are correct. My opinion is the "chain will be too short/drivetrain will break" argument is missing the obvious.

    I always suggest sizing the chain according to the "big-big" method prescribed by both Shimano and SRAM, no matter what cage length is chosen.

    <img src="http://www.booboodog.net/images/chainlength.jpg">
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  34. #34
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    I'm still not completely understanding this and I've read this thread twice in the past two days.

    I busted my derailleur and hanger tonight after a pretty nasty spill on asphalt; the turn was pretty sharp, I was goin pretty fast, and I missed a wet spot... So, now I'm in need of a new derailleur for my GT hardtail. I've got a new FS frame on the way as well, and this new rear derailleur I would like to be compatible with my new frame.

    Everything on the GT 1.0 is still stock since when I ordered it almost 10 months ago. So I'm assuming it has standard cogs up front, and standard rings in the back. The only thing I cannot confirm is whether or not the chain has been sized correctly. From that picture that Nate posted, it looks to me as if they left no room at all for a derailleur in the big-big combination... correct?

    I'd like to get the smallest derailleur possible, while still retaining the ability to use the majority of my gears. I like the crisper shifting, and reduced chain slap benefits of the smaller cage. However, I need someone to help me pick one out.

    Also, are chains usually sized correctly right from the factory?

  35. #35
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    Quote Originally Posted by bigsurf75
    From that picture that Nate posted, it looks to me as if they left no room at all for a derailleur in the big-big combination... correct?

    I'd like to get the smallest derailleur possible, while still retaining the ability to use the majority of my gears. I like the crisper shifting, and reduced chain slap benefits of the smaller cage. However, I need someone to help me pick one out.

    Also, are chains usually sized correctly right from the factory?
    Correct... well, sort of. When you do the "big-big+2" and actually shift the bike into the big-big combo, the derailleur cage should be sticking pretty well forward. That's the intention.

    My impression is that stock chains are often a few links long, but not always. Also take into account chainstay growth when the suspension cycles.

    With stock 27-speed gearing, you can definitely get away with a snappy shifting medium cage. Just know your limitations: shifting to maybe 1/2 of your small-small gears will result in no chain tension, and likely a dropped chain.
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  36. #36
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    I wonder if I could shorten the chain enough to make a 1/4 of the small-small combos unusable, and a 1/4 of the big-big combos unusable.

    I think I would probably find myself using these combos less frequently.

  37. #37
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    Quote Originally Posted by bigsurf75
    I wonder if I could shorten the chain enough to make ... a 1/4 of the big-big combos unusable.
    Yes, absolutely. But is is prudent? Maybe 99.9% of the time you'll catch yourself. But all it takes is that one epic ride, topping that forever long climb, transitioning into a saliva-inducing descent (maybe a little short of O2 to the brain), when you mis-shift and rip your rear derailleur into your spokes, or bend the big chainring, or fold over your cassette.

    So yeah, it'll work, but it's a personal call with risks to consider. I'd never recommend it.

    <img src="http://www.booboodog.net/images/bent-surly-ss-ring.gif">
    Last edited by Speedub.Nate; 01-06-2008 at 04:06 AM.
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    Hmm, Maybe I will just go with a long cage.

    However, at the same time I was looking at BR's in a few other threads and I may make the switch to a 2x9 with a 24-36 up front. I'm gonna try riding around for a day or two ( I think I can nurse two days out of the busted deraileur) without using the big ring and see if I miss it. If that's the case, I'm goin to a med. cage rear.

  39. #39
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    Speedub.Nate.......Thanks for your explanation!!! Great job!!!

    I'm using 44-32-22 crankset & 11-34 cassette, and deciding to buy a new sram X.0 med cage RD. But I still have a question about how to determine the proper chain length.

    Somebody told me that when I shift the chain on the largest chainring on the front and the smallest cog on the rear, if the the top pulley is sitting directly above the lower pulley, the chain is the proper length. So, can I apply this theory if I'm using a med cage RD?

    Thanks!!!

  40. #40
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    Quote Originally Posted by Sealama
    ...I still have a question about how to determine the proper chain length.
    Stick with the Big-Big +2 technique I posted the graphic of a few posts up (post #33). That's the best way to ensure you have just enough chain to shift to Big-Big without breaking anything.
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  41. #41
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    The new stumpy is equipped with a Med cage and it's standard up front and 11-34 out back.

  42. #42
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    Quote Originally Posted by HTail
    I'm finding my SRAM XO med cage works great with 11-34 cog. In fact it can accommodate the extreme large-large gear combo, but as we all know, it's not recommended with full-susp bikes (chain growth upon compression). The shifts are definitely snappy, quick and precise- partly due to the shorter cage, and mostly to SRAM's shift system.
    It's a myth that a shorter cage shifts better. The shift is made when the ramps line up with the chain on the cassette. If your chain hangs slack in some gear combinations, you're more prone to skipping or chain suck in those gear combinations.

  43. #43
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    Quote Originally Posted by MikeDee
    It's a myth that a shorter cage shifts better. The shift is made when the ramps line up with the chain on the cassette. If your chain hangs slack in some gear combinations, you're more prone to skipping or chain suck in those gear combinations.
    Is your "myth" assessment coming from analyzation or from use out on the trail? I suspect the former. Cage length does make a noticable difference in shifting and performance.

    Sure, shift ramps help some with a shift, but they're not necessary. The shift occurs when the idler pulley on the derailleur (that's the upper wheel) changes alignment with the cassette cog.

    But behind that is maybe sixteen inches of chain, stretching from the lower tensioner pulley (that's the lower one) to the chainrings.The further away that chain is from the anchor point / pivot points of the derailleur, the more difficult it is to move precisely. Think of a fat piece of nigiri at the end of a L-O-N-G set of chopsticks.

    As for your "chain slack" assessment, it's not as if the derailleur cage is magically decreasing in tension in certain useable gear combinations. Either is doesn't have tension in certain unusable small-small combos (as previously discussed), or it's got FULL tension (and, more importantly, higher tension than a longer cage -- simple physics there).

    If my some Shimano voodoo longer cages shifted better and held better tension, that's all they would offer, and roadies would be riding with derailleur cages hanging scant millimeters off the ground.
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  44. #44
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    I have a X.9 Med cage sitting here on my desk along with a set of X.9 shifters (series prize), and am thinking about putting them on the new Anthem (which has a Shadow on it). However given I have tons of 11-34 spares and only a Deore 11-32 sitting around, for now I might have to leave the XT on there - since numerous people have pointed out the problems of putting a Med cage with an 11-34 cassette on a duallie.
    Quote Originally Posted by tom2304
    Yep farkin.net is mostly immature kids asking how to put dual crown forks on hardtails and such.

  45. #45
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    i need help. im running a x0 short cage with a 11-23 cassette and a 38T front chainring. should i be running a short cage or long cage??
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  46. #46
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    Quote Originally Posted by downhillross13
    i need help. im running a x0 short cage with a 11-23 cassette and a 38T front chainring. should i be running a short cage or long cage??
    Do you mean 11-32 cassette? Either way, you are fine with a short. Run the numbers for yourself - Nate laid it all out for you on the first page using caveman-easy math.

    Cheers, Chris
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  47. #47
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    Quote Originally Posted by Trentkc
    I have a new SRAM X9 long cage derailleur, and another X9 that I now realize is "not long". Both are brand new, but the short one is ~16mm shorter.

    What is the proper application for long versus short cage derailleur? Will the short one work with a 11/34 cassette? Does it matter if the bike has a rear suspension or is a hardtail?

    Is my shorter X9 a "short" cage or "medium" cage? Thanks //kct
    General rule

    1 ring - short cage
    2 rings - medium cage
    3 rings - long cage

    Since us MTBers typically use the largest range cassette possible, I think this is a pretty good rule.

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    naw im running a dura-ace 11-23 cassette. yea i did the math and ended up with 50T. i dont know what the range is per dif. type of cage
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    Quote Originally Posted by downhillross13
    naw im running a dura-ace 11-23 cassette. yea i did the math and ended up with 50T. i dont know what the range is per dif. type of cage
    Gotcha. With only a single ring up front, the first part of Nate's equation is 0 (whatever ring size minus itself), so all you have to account for is the 'big cog minus small cog' teeth spread. That's basically what's behind the "single ring -> short cage" rule-of-thumb.

    Cheers, Chris
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    Quote Originally Posted by willtsmith_nwi
    General rule

    3 rings - long cage
    Generally the "safe" recommendation, especially if you don't want to go through the lengthy explanation and/or math. I enjoy the benefits of the medium cage on my 3x9, however.

    Rules of thumb are great, but it's good to know what's at the foundation of the rule, too.
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  51. #51
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    xtr vs xo

    Quote Originally Posted by Speedub.Nate
    Right! Think of the cage as a lever arm. As you know, a longer lever is easier to displace against a fixed counter force.

    In this case, the fixed force is the tension spring, which is same spring regardless of which cage length it is installed on.

    The bouncing chain is attempting to operate the lever arm (derailleur cage) and displace the spring. Longer cage = easier to move. Shorter cage = more difficult.
    ~~~~~~~~~~~~~~~

    Echoing the others: Thanks so much! Your posts have been quite educating.

    Now my question would be (for Speedub.Nate , or for anyone who would know): For an apple-to-apple comparison, which one (which brand) has the higher/stronger tension spring (ie. xtr med vs xo med)? Has anyone done any actual measurments to compare?
    Thanks in advance!

    Cheers!

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    Its pretty obvious that the Shimano short (GS) cage length is tailor made for the Ultegra 12-27 cassette and 22-32-44 triple combo. . .

    I've been running said combo since early '05 and have not missed the 44-11 gear at all. I ride a road bike and learned to spin decades ago. I really find little need to go much faster than that on a hardtail anyway. Runs nice and quiet and affords much tighter ratios for fine tuning on fireroad time trial sections. I use the phat low mount style XT front D so I can confidently bail to a lower chainring and have NEVER dropped the chain with that long pivot masterpiece.

    And. . .since my pushed/shoved Xtc weighs less than 21 lbs I never need any lower than the 22-27 granny either. I find myself making up lots of time climbing 1mph faster too.

    Hey thanks for the clarification and chart that shows me I'm locked outa the 11-32 as I had suspected, but never really tried.

  53. #53
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    Sorry to bring this back from the dead.
    But I need a new derailleur pretty bad. Im looking at either a short cage x9 or med cage.

    As of now Im running a single 32 up front with the possibility of going to a 34 for the summer. With a road cassette 12-23 in the back.

    What would you run and why?
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  54. #54
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    Quote Originally Posted by motormonkeyr6
    Sorry to bring this back from the dead.
    But I need a new derailleur pretty bad. Im looking at either a short cage x9 or med cage.

    As of now Im running a single 32 up front with the possibility of going to a 34 for the summer. With a road cassette 12-23 in the back.

    What would you run and why?
    Short. Why would even consider (given the choice) using a medium with that setup?

    Cheers, Chris
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  55. #55
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    Quote Originally Posted by Chris130
    Short. Why would even consider (given the choice) using a medium with that setup?

    Cheers, Chris
    My bike see's alot of abuse, its all Freeride and DH so maybe with a longer derailleur the load would be lessend on the derailleur itself.

    Would a short accommodate a 12-27 cassette?
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  56. #56
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    Quote Originally Posted by motormonkeyr6
    My bike see's alot of abuse, its all Freeride and DH so maybe with a longer derailleur the load would be lessend on the derailleur itself.

    Would a short accommodate a 12-27 cassette?

    the cassette is a moot issue more or less, when running a single ring, you want the shortest cage possible.

    i run a 36T ring up front with a 11-26 road cassette. you'll be fine.

    i also have a spare wheelset with a 11-34 cassette - the short cage works fine here too.
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  57. #57
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    Quote Originally Posted by jcaino
    the cassette is a moot issue more or less, when running a single ring, you want the shortest cage possible.

    i run a 36T ring up front with a 11-26 road cassette. you'll be fine.

    i also have a spare wheelset with a 11-34 cassette - the short cage works fine here too.
    Thanks for clearing that up guys!
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    Still needing help



    Ok...I've read and re-read but still am finding this a bit confusing. First with my setup. I ride a full suspension with 11-32 and 22-44. I will be replacing my current Shimano XT rear derailleur (long cage) and would like to know if I would benefit using a medium cage (2008 Shimano XT). If I size the chain to Big-Big+2 how do I take into account for the rear suspension? Also, after sizing the chain, would I be able to use ALL the gear combinations with no problems or would I have to make sure not to use certain combos? I don't want to have to worry about shifting into the wrong gear so should I just stick with a long cage?

    Any help would be really appreciated.

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    Quote Originally Posted by 1singletrack


    Ok...I've read and re-read but still am finding this a bit confusing. First with my setup. I ride a full suspension with 11-32 and 22-44. I will be replacing my current Shimano XT rear derailleur (long cage) and would like to know if I would benefit using a medium cage (2008 Shimano XT). If I size the chain to Big-Big+2 how do I take into account for the rear suspension? Also, after sizing the chain, would I be able to use ALL the gear combinations with no problems or would I have to make sure not to use certain combos? I don't want to have to worry about shifting into the wrong gear so should I just stick with a long cage?

    Any help would be really appreciated.
    if you're sticking with the 3x9, then you're probably going to want to retain the long cage...you can go with a medium cage, but you'd have to be mindfull of your shifting, ie: no big-big combo (44 up front, 32 in the rear) which you shouldnt't be doing anyway as that is major cross-chaining.
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    Quote Originally Posted by 1singletrack
    I ride a full suspension with 11-32 and 22-44. I will be replacing my current Shimano XT rear derailleur (long cage) and would like to know if I would benefit using a medium cage (2008 Shimano XT). If I size the chain to Big-Big+2 how do I take into account for the rear suspension? Also, after sizing the chain, would I be able to use ALL the gear combinations with no problems or would I have to make sure not to use certain combos? I don't want to have to worry about shifting into the wrong gear so should I just stick with a long cage?
    The total capacity you need is 44-22+32-11, or 43. Shimano recommends 33 or thereabouts for their medium cage, so you're definitely a candidate for the long cage. If you use the medium cage, the derailleur will be unable to take up all the slack chain for certain gear combinations and you'll have a drooping chain.

    When you're sizing your chain, move the suspension through it's range of travel (taking out your shock or deflating it can help with this), and see what the max chain length required is. Use the big-big+2 rule at that max length to size the chain.

  61. #61
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    Quote Originally Posted by jcaino
    if you're sticking with the 3x9, then you're probably going to want to retain the long cage...you can go with a medium cage, but you'd have to be mindfull of your shifting, ie: no big-big combo (44 up front, 32 in the rear) which you shouldnt't be doing anyway as that is major cross-chaining.
    No... no small-small combos. Always size your chain to accept a shift into big-big, unless you're willing to deal with the consequences.
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    Quote Originally Posted by 1singletrack
    Ok...I've read and re-read but still am finding this a bit confusing.... I don't want to have to worry about shifting into the wrong gear so should I just stick with a long cage?
    In your case, with your statement, yes, stick with long cage. That will cover you in all possible gears without having to "worry about shifting."

    Once you're willing to avoid cross chaining to small-small, a medium cage would likely work fine on your setup.

    As for measuring chainstay growth, get a piece of dental floss and tie it on your crank's spindle. Zip tie the loose end to your rear quick-release -- so it's taut, but still slides when you tug on it. Now cycle your suspension, then go back to the dental floss. It should be hanging a little loose, unless your bike is a URT or BB-concentric pivot. Pull the floss taut again through the zip tie. For each 1/2" of floss you pull through the zip tie, you'll need to add an inch (2 links) of chain to account for chainstay growth.
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    Quote Originally Posted by Speedub.Nate
    Once you're willing to avoid cross chaining to small-small, a medium cage would likely work fine on your setup.
    Speedub.Nate...so if I do decide to go with the medium cage, the only gear combination I would need to avoid is the small-small one with my 11-32+22-44? If that's it then perhaps I'll go with a medium in order to have crisper, more precise shifting. Also, thanks for the tip on sizing the chain with a FS bike.

    Thanks so much guys for getting back to me so quickly...this forum is absolutely amazing.

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    Quote Originally Posted by 1singletrack
    Speedub.Nate...so if I do decide to go with the medium cage, the only gear combination I would need to avoid is the small-small one with my 11-32+22-44? If that's it then perhaps I'll go with a medium in order to have crisper, more precise shifting. Also, thanks for the tip on sizing the chain with a FS bike.
    Take a look again at that color table I put together in the first post. All the gear combinations in green are ok to use. The ones in yellow and red -- the smaller half of your cassette range when you're in your smallest chainring -- are going to be the ones you'll want to avoid using.

    The grey ones are "big-big," and though you'll size you chain accordingly so that shifting to these combos won't damage anything, these cross-chain combos are best avoided, no matter what cage length you choose (due to chain stress & drivetrain wear).
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    It would probably be more than just the small-small combo, a few more combinations up I would imagine. If you accidentally shift into one of the no-no combos you won't damage anything, but you could drop your chain. Honestly I would just go with the long cage, it was made for the triple ring.

  66. #66
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    guys...i know i might be kicking a dead horse all over again, but i need some guidance...ok, i raced for the first time, and i decided to become a weight wenie....thus far, i came up with some weight reductions...my bike dropped about 3 lbs...so i have been looking at the possibility to throw a short cage derailleur and go 2x9...please either explain a bit more to me about the pros and cons of doing this or guide me to the right forum or thread...i will really appreciate it...

  67. #67
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    Quote Originally Posted by doctorholguin
    ...so i have been looking at the possibility to throw a short cage derailleur and go 2x9...please either explain a bit more to me about the pros and cons of doing this or guide me to the right forum or thread...
    With a 2x9 setup you may be able to use a short cage der, and almost certainly a medium cage.

    Take the difference in teeth of your max and min cogs, and the difference between the chainrings, and add them up. For example, if you want to run an 11-34 in the back and 22-32 in front, the difference is 23 in back, and 10 in front. For a total of 33. Your chosen derailleur should have a max capacity of at least that much.

    In the same example, if your derailleur has a capacity of less than 33, it's still no big deal. Size your chain to accept the big/big combo, and just remember to never shift into small/small, because the derailleur may be unable to take up all the chain slack, and your chain will droop. Conversely, you can size your chain a few links short, so that it's okay in the small/small combo, but then you should never shift into big/big because it may damage your derailleur.

  68. #68
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    Quote Originally Posted by doctorholguin
    ...so i have been looking at the possibility to throw a short cage derailleur and go 2x9...please either explain a bit more to me about the pros and cons of doing this or guide me to the right forum or thread..
    Lyndonchen hit all the points you need to consider, but here's where 2x9 is different:

    With 3x9, you're always going to have a bunch of cross-over gears and "illegal" cross-chain combinations. It's those illegal gears that allow a medium (GS) cage to be used on a triple-ring setup.

    With 2x9, you're eliminating a bunch of cross-over gears, but you're not necessarily eliminating cross-chain combinations that should be avoided. It depends on where you set your chainline. In theory, the entire 2x9 range could be useable.

    But you may want to set it up with where one ring or the other (your primary chainring) is centered on the cassette, for optimized use of the full range of gears, or you may want to bump your outer ring out for better chain alignment in your hammer gears. All depends.

    So basically: Make a gearing matrix like the one in my original post. Decide what gears you want to use, and highlight those that you consider unnecessary (if any).

    For certain, medium cage will work with any full-range 2x9 setup. Based on your needs, a short cage <i>may</i> work if you're planning to eliminate some gear combinations.
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    New question here. Chain suck potential?

    Anyone want to comment more on chain suck potential when one has a choice between Long vs Med cage? My hypothesis is that with a long gage the "lever" is longer thus keeping more tension on the chain in the granny gear(22/34 in my case). My experience is the opposite I have on bike with XTR med cage and never get chain suck. I have another with long cage X0 and get chain suck in dirty conditions. Both are typical 22-32-44 , 11-34.

  70. #70
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    Quote Originally Posted by sheppardk
    My hypothesis is that with a long gage the "lever" is longer thus keeping more tension on the chain in the granny gear(22/34 in my case).
    It's exactly the opposite. Switch it up, and think of the derailleur cage as the lever arm that allows the bouncing chain to act against the tensioner spring.

    The chain has more authority over the tensioner spring when connected by longer cage lengths; less with shorter.

    That's the reason for the quieter drivetrain when shorter cage lengths are used.
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  71. #71
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    Med cage good

    I've been running a medium XO for a year now and finding it works fine, even when accidentally in extreme cassette/chainrg combos. I've also noticed I haven't gotten chain suck since switching to the med cage derailleur.

    In general just very happy with SRAM XO versus my previous Shimano XTR.
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  72. #72
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    Quote Originally Posted by lyndonchen
    The total capacity you need is 44-22+32-11, or 43. Shimano recommends 33 or thereabouts for their medium cage, so you're definitely a candidate for the long cage. If you use the medium cage, the derailleur will be unable to take up all the slack chain for certain gear combinations and you'll have a drooping chain.

    When you're sizing your chain, move the suspension through it's range of travel (taking out your shock or deflating it can help with this), and see what the max chain length required is. Use the big-big+2 rule at that max length to size the chain.
    lyndonchen, you are treating the chain sizing issue separate from the cage sizing issue for full suspension. If you have to add chain (beyond the standard big-big +2) to account for chain stay growth, the dérailleur has to take up that extra chain when the suspension is in it's "short chain" position.

    Based on everything I have read in this thread, it seems like the process should be:

    1. Determine chain length using Big-Big + 2 + (2 links for each 1/2 inch of chain stay growth)
    2. Determine cage size accounting for extra links for chain stay growth, where:
      cap req'd (T) = (BIG ring - small ring) + (BIG cog - small cog) + (extra links)

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    This is a a great thread - Thanks speedub.nate.

    I agree that med cage seems like a much better choice in most situations. Last week I got a med cage X0 and replaced a long cage X9 and there is much more chain tension with low gears. It is also quieter and I have had no chain suck so far. On my normal ride I ride through a small creek. If I had not cleaned my chain for more then a couple of rides then I would get chain suck going uphill after the creek. I have ridden 5 times(about 7 hours) without cleaning my chain and have had not chain suck with the med cage X0. The proof will come when I ride in the mud, but so far so good. It is hard to understand why one would choose a long cage for most cases.

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    After installing the med cage a couple yrs ago, I thought I'd have to baby it on the trails, but just the opposite, it actually feels more robust. I really think the long cage is overkill, unless they go to 10 speeds someday.

    I also think that those of us that ride regularly also use a narrower range of gears, for instance, rarely use the granny + I'm not doing a lot of technical stuff day to day. Maybe long cage is better for those that need the wider range either because of the trails or personal heft!
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  75. #75
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    The sticky pointing to this thread says there is no short cage X9, only X0. I thought I have a short X9, and one is mentioned in this thread... I'm confused! I know have 1x9 and need to switch to 2x9, trying to decide if I also order a new rear deraileur...

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    Quote Originally Posted by dropadrop
    The sticky pointing to this thread says there is no short cage X9, only X0. I thought I have a short X9, and one is mentioned in this thread... I'm confused! I know have 1x9 and need to switch to 2x9, trying to decide if I also order a new rear deraileur...
    Where's the confusion?

    A quick Google search shows lots of short cage X.9s available, and lists a chain capacity of 32T.

    Note the date of the original post. Product lines change. The calculation remains the same -- all you need to know is your derailleur's chain capacity.
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    short cage rear derailleur

    interesting thread!

    question:
    what is the biggest cog a XTR RD-M950 short cage can catch (yep, pretty old rear derailleur )?
    Can this take up to 28 tooth in the rear? Or is it recommended to use this one with a road cog set, lets say 12-26?

    thanks!
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  78. #78
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    Quote Originally Posted by Speedub.Nate
    Where's the confusion?

    A quick Google search shows lots of short cage X.9s available, and lists a chain capacity of 32T.

    Note the date of the original post. Product lines change. The calculation remains the same -- all you need to know is your derailleur's chain capacity.
    Thanks. I should have looked at the date, I just thought the sticky had all the essential information from this thread combined and updated and did not think about googling.

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    Rather than use the generic formula, let's map out the capacity for each gear combination (based off of a Shimano cog pattern; SRAM will be slightly different):

    <img src="http://www.booboodog.net/images/derailleur-capacity.gif">
    THanks, Awesome!!! Now I finally know why when I am in my 1-9(short-short) gear while biking it sounds like it is an unstable gear and like it doesn't want to be there. Which makes me shift either to 1-8 or up to 2-5. Great Post.

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    Nate -

    I didn't do very well in math class... If I have a 11/34 cassette and only run two rings up front (small & medium w/ bash guard, no big ring) , should I use a SRAM short or medium cage and what length chain? Thanks a ton!

    (P.s. You have my vote for the 2008 Nobel peace prize ! http://nobelprize.org/ )

  81. #81
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    Quote Originally Posted by gregoryb02
    Nate -

    I didn't do very well in math class... If I have a 11/34 cassette and only run two rings up front (small & medium w/ bash guard, no big ring) , should I use a SRAM short or medium cage and what length chain? Thanks a ton!

    (P.s. You have my vote for the 2008 Nobel peace prize ! http://nobelprize.org/ )
    you can use a short cage, providing you dont cross-chain, and use the big-big combo, which shouldnt be done anyway.

    a medium would also work wonderfully.
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  82. #82
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    Quote Originally Posted by jcaino
    you can use a short cage, providing you dont cross-chain, and use the big-big combo, which shouldnt be done anyway.

    a medium would also work wonderfully.
    A medium cage is the safe bet and a necessity if the bike has a high forward single pivot (think Santa Cruz Bullit).
    Thats with two rings, no bigger than about 38 on the big ring.

    I just found all this out, the hard way tonight.
    I bought a med cage dérailleur for my single pivot by mistake.
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    Great Read! Thanks alot guys, especially Nate!

    I just ordered my SLX 662-GS (Med Cage). for my 2x9 and probably eventually 1x9 setup.

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    Quote Originally Posted by ZenkiS14

    Great Read! Thanks alot guys, especially Nate!
    Hey, no problem, you're welcome. The ironic thing is that I haven't used derailleurs since about 2002, with a couple of exceptions.
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    Yeah But...

    When asked about a 1x9 setup and der size requirements:

    Quote Originally Posted by Speedub.Nate
    That's an easy one... go as short as you can possibly go.

    See, it's not the *size* of the front chainring that factors in, but the *range* between the biggest ring and the smallest ring.

    With an 11-32 in the rear, you've got a 21T spread, well within the capacity range of Shimano's short cage derailleur.

    (The capacity requirement for the front rings is Zero on your setup because it doesn't change at all.)
    I have a Ultegra short cage der on its way for my new 1x9 hardtail. The spec on the Shimano website states:
    Maximum Sprocket 27T
    Minimum Sprocket 11T
    Maximum Front Difference 16T
    Total Capacity 29T

    I get the "Total Capacity" limitation from the above, most excellent explanation, however I am concerned that the "Maximum Sprocket" may make my 11-34 unusable in the lower two gears on the cassette.

    So, whaa???

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    Quote Originally Posted by chexem

    I have a Ultegra short cage der on its way for my new 1x9 hardtail. The spec on the Shimano website states:

    Maximum Sprocket 27T

    …I am concerned that the "Maximum Sprocket" may make my 11-34 unusable in the lower two gears on the cassette.
    Yeah, there's a "rise" and a "reach" component: the reach is the easy part, but the rise (will the derailleur clear the cog?) is the question. And that's independant of cage length, since the body of the derailleur seems to remain constant with any particular model.

    What I can tell you is I ran a short cage road derailleur on a 1x9 setup on a folding bike recently (before converting it over to a gear hub). The cassette was a mountain range 11-32T. The derailleur was either Ultegra or Dura Ace, can't remember.

    I had to snip a portion of the cage off, the part that loops around the guide pulley. But it was due to a clearance issue with the frame. The pulley cleared the cassette with no trouble.
    speedub.nate
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    I'm just checking to see if all of my drivetrain will be compatible when I set it up: 11-32 Sram Cassete, Sram x7 rear derailleur short cage, sram x7 front derailleur low mount, truvativ stylo 22-32-44, and sram pc 991 cross step.
    thanks

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    Quote Originally Posted by RebaRox246
    11-32 Sram Cassete, Sram x7 rear derailleur short cage, sram x7 front derailleur low mount, truvativ stylo 22-32-44
    Your rear derailleur needs to have a chain capacity of 43 or more. (44-22)+(32-11) = 43. I don't know what the capacity of the short cage is but it's likely not enough.

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    Quote Originally Posted by RebaRox246

    I'm just checking to see if all of my drivetrain will be compatible when I set it up:
    I'd go nothing shorter than a medium cage if you're ok with the limitations outlined in the original post.
    speedub.nate
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  91. #91
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    Med cage good

    I agree med. cage is the best all around. You can still push the large/small gear limits (though not recommended) and still get more taught chain tension and spiffy shifting.
    Question to a custom frame builder..."So what makes your bikes climb better?"....his answer, "Uh, your legs?"

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    I want to change the 11-34 on my cannondale bad boy to a road 11-23 or 12-26, should I go for a X9 medium cage at the back instead of the long cage I have now?
    Thanks all

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    You can use a med cage on 11-34, with marginal performance at the extremes. Definitely if your gearing higher, go for a med cage to keep the chain taught.
    Question to a custom frame builder..."So what makes your bikes climb better?"....his answer, "Uh, your legs?"

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    Quote Originally Posted by mrwibble
    I want to change the 11-34 on my cannondale bad boy to a road 11-23 or 12-26, should I go for a X9 medium cage at the back instead of the long cage I have now?
    Thanks all
    Depending on your ring setup (if you're running doubles), you could go short cage.
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    Speedub.Nate spent the night at a Holiday Inn

    Short cages tend to pack quicker during wet conditions - there's not enough room between the pulleys.

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    Quote Originally Posted by emptybe_er

    Speedub.Nate spent the night at a Holiday Inn
    I totally agree! I used to be the night auditor. Spent the night? I had the run of the damn joint! Night after night after night after.... zzzzzz....

    Uh, what'da ya say?!?

    The only thing better than short cage is no cage!
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    Forgot to say guys, chainring is 48-36-26 again with long cage X-9

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    Quote Originally Posted by mrwibble

    chainring is 48-36-26
    Then medium cage, for sure.
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  99. #99
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    Go Short (SS) Cage

    An SS cage will have no problem with a 12-26 and 48-36-26 gearing.
    *** --- *** --- ***

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    sorry i meant medium cage, i don't think they make a X7 short cage

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