What's the difference between short cage and medium cage Rear Derailleur?

Discussion in 'Cycling Equipment' started by biserker1, Jun 14, 2011.

  1. biserker1

    biserker1 New Member

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    Wanted to know the difference between the two. Is one better then the other??

    An example Shimano RD 6700 GS vs Shimano RD 6700 SS

    one more question: what's the significance between a rear casset that is 11 - 28 vs 12- 27?


    Thanks!
     
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  2. alfeng

    alfeng Well-Known Member

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    FWIW. I would always choose the rear derailleur with the longer cage & the front derailleur with the wider inner plate (i.e., the front derailleur which is Triple-capable) UNLESS I knew that I was always going to use a tight ratio rear cluster ...

    The longer GS cage allows for more drivetrain options without worrying about the chain become slack ...

    • a slack chain is more of a problem with MTBs ... and, is mostly a cosmetic issue with Road bikes

    In the distant past, so-called Touring rear derailleurs were not as stiff & the shifting was considered to be slightly less precise -- that may have been more fiction than fact and/or a matter of comparing apples with oranges (i.e., comparing a Campagnolo rear derailleur with a Huret rear derailleur). Regardless, I don't believe that there is a perceptible difference with how well a short cage or a medium cage or a long cage derailleur functions (at least, Shimano's in the past dozen years, if ever), now ...

    The actual chain length does not have to be any longer with a long cage rear deraiIeur for any given combination of chainrings & cassette cogs than it would be with a short cage rear derailleur; but, if the chain which is in place is maximized for the long cage derailleur's capability, then the 4-or-more additional links will be dragged around as the rider pedals.

    • Professional racers have derailleurs with short cages

    I would generally choose the cassette with the wider ratio ...

    BUT, the tighter ratio allows the rider to potentially maintain a more consistent cadence -- if you don't need an 11t (few do for riding on most roads), then having an 11t cog excludes having an intermediate cog.

    FYI. By my reckoning, the reason that Shimano originally had a cassette with only a 27t largest cog was the consequence of implementing 11t pulley wheels ... that is, a 27t cog was the largest cog that could be safely implemented if those derailleurs were installed on an older frame which had a minimum-drop derailleur hanger which had been designed for the vertical Campagnolo Nuovo Record rear derailleur.

    IMO, if you need a 27t, you may as well get the cassette with the 28t cog; otherwise, you may want to consider a cassette with a 26t-or-smaller largest cog ...

    • the terrain you ride on & your strength should determine the range of cogs on the cassette you use
     
  3. biserker1

    biserker1 New Member

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    Thanks for all this info!

    My bike currently has 12 - 27 back cog with a medium rear DR. All Shimano 105 with a compact crank 50/34. My shifters are Shimano Ultegra. I thought about taking the cog, chain, back/front DR up to ultegra so i have matching group.

    Would the 11 - 28 cog be the better choice? Also per you recommendation i would go with a medium cage back DR? would the short DR also work with this set-up?

    Thanks again!
     
  4. An old Guy

    An old Guy Member

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    It is sort of foolish to change components just to make them match. But I have done foolish things in the past.

    It is difficult to know what cassette to recommend without knowing more about how strong you are. But if you are using compact gearing, most likely you do not need the big gears.

    I have been happy with a 16-27 (16,17,18,19,20,21,22,23,25,27) Shimano Ultegra 6600 10 speed B (junior gearing). I have no desire to pedal over 30mph and a 27 gets me up the hills a bit easier than a 25.
     
  5. biserker1

    biserker1 New Member

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    ok, good advice. New to cycling and trying to figure this all out. I thought that a matching group would perform better then a mixed.
     
  6. swampy1970

    swampy1970 Well-Known Member

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    The only real difference between the short and medium cages for the road groups are their ability to handle double or triple chainsets. If you plan on using a double (either standard 53/39 or a compact such as 50/34) then a short cage will work fine. If you ever need to use a triple chainset then you would at least need a medium cage 105 or ultegra. If you wanted to run a cassette with more than 28 teeth then you'll need something like a Deore long cage. The latest dura ace, ultegra and 105 offer a 28 tooth rear, the prior versions only do a 27. Shimano say the slightly older rear mech such as the 6600 ultegra will not handle the 28... But in the real world it'll probably work fine.
     
  7. biserker1

    biserker1 New Member

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    The only real difference between the short and medium cages for the road groups are their ability to handle double or triple chainsets. If you plan on using a double (either standard 53/39 or a compact such as 50/34) then a short cage will work fine. If you ever need to use a triple chainset then you would at least need a medium cage 105 or ultegra.

    If you wanted to run a cassette with more than 28 teeth then you'll need something like a Deore long cage.

    The latest dura ace, ultegra and 105 offer a 28 tooth rear, the prior versions only do a 27. Shimano say the slightly older rear mech such as the 6600 ultegra will not handle the 28... But in the real world it'll probably work fine.

    Is there a real difference in feel between the 27t and 28t? I have been riding a 27t and really working on my climbing skills. I just did a 32 mile ride that had a good amount of climbing although there were no rated hills. I noticed some guys sitting and spinning pretty fast while i was out of the saddle really pushing it.
     
  8. Adam-from-SLO

    Adam-from-SLO New Member

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    the difference between a 28T - 27T = 1 tooth /img/vbsmilies/smilies/smile.gif
    Thus, the 28T will have a slightly larger circumfrence then the 27T ring. In which case, the 28T will be slightly easier to push when riding uphill (given the same front chainrings being used).

    So, the only way to use a 11-32 or 11-34 cassette on a road bike (if using Shimano 10-speed shifters), is to go with a mountain bike rear-derailleur (like Deore, XT, etc. , with long cage ) ? Can a Ultegra Medium cage do a ring larger then 28T ?
     
  9. alfeng

    alfeng Well-Known Member

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    You must have been away during recent discussions ...

    Here are two bikes which I set up which have Shimano ROAD rear derailleurs ...

    This is the drivetrain on my OLMO which has a Shimano 105 rear derailleur + 11-32 XT Cassette:

    [​IMG]

    This is another drivetrain which has a Shimano DA rear derailleur + 12-34 XTR Cassette:

    [​IMG]

    Some people say that they can simply adjust the B-screw to achieve clearance for an 11-32 Cassette ...

    In both cases, I replaced the 11t upper pulley wheel with a 10t pulley wheel ...

    • for the OLMO, due to the short derailleur hanger, I also needed to adjust the B-screw so that the smaller 10t jockey wheel could clear the 32t cog
     
  10. oldbobcat

    oldbobcat Well-Known Member

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    So the 28t cog will be 1/27th easier than the 27t. That's 3.7 percent.

    And, yes, the only way to use a wide range MTB cassette for 10-speed Shimano shifters is to use a non-10-speed Shimano MTB rear derailleur. Pull rates are the same for all Shimano rear derailleurs except the new 10-speed MTB range.

    And no, the Ultegra GS will nominally not handle more than a 28t cassette cog. That's because the length of the body is the limiting factor on cassette size, and the GS and SS derailleurs use the same body. The GS extends just the cage, which only takes up more chain slack, which only allows a wider range of chainrings up front.

    The length and shape of the derailleur hanger are also factors in the actual maximum cog that the derailleur can handle. Many riders and other tinkerers have extended the range of their road derailleurs by fiddling with the B-screw, flipping the B-screw, or substituting a longer B-screw. Shimano makes no promises to reward this kind of resourcefulness. In other words, your own mileage may vary.

    If I had a foundry I would manufacture extra long derailleur hangers for the popular road bikes.
     
  11. okhealthy

    okhealthy New Member

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    i agree "the difference between a 28T - 27T = 1 tooth
    Thus, the 28T will have a slightly larger circumfrence then the 27T ring. In which case, the 28T will be slightly easier to push when riding uphill (given the same front chainrings being used)." good job! thax @biserker1 . /img/vbsmilies/smilies/biggrin.gif [​IMG]
     
  12. ambal

    ambal Active Member

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    What a stupid discussion..... several years later. :ph34r:
     
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