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  1. #1
    Habitual (Bike) Tweaker ATX 6Speed's Avatar
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    Swapping Rear Derailleur Cages?

    I'm looking to swap the SGS (long) cage on my Shimano XT M771 rear derailleur with a GS (medium) cage off of a Shimano XT M771. The derailleurs are pretty much the same minus the cage length, so will this be doable? If so, how would I go about getting the parts for the changeover?

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    bike whisperer Kimmo's Avatar
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    I'm certain it's doable. You can prolly swap the cage from a whole bunch of Shimano derailleurs.

    Whether you can get the cage as a spare is another thing... NFI. But it doesn't sound too urgent...

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    Gear Combo Guru Chris_W's Avatar
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    I recently replaced an Ultegra short cage with a medium cage from a 105 that had a broken knuckle. It was pretty straightforward, and the resulting derailleur looks and works as it should.

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    Habitual (Bike) Tweaker ATX 6Speed's Avatar
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    Awesome, I'm wondering where I'd be able to find a replacement cage. Do you think Shimano sells the inner plates?

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    that's great for sure.

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    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by ATX 6Speed View Post
    I'm looking to swap the SGS (long) cage on my Shimano XT M771 rear derailleur with a GS (medium) cage off of a Shimano XT M771.
    After you do that, what do you think you will have accomplished?

  7. #7
    Bianchi Goddess Bianchigirll's Avatar
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    I doubt that you would be able to find the parts as replacement/spare parts. most component compaanies don't work that way. your best bet is to find a broken donor derailer like Chris did.
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    Retro Grouch's question is a good one. After all of that work, what will you have accomplished or improved?

    As to replacement parts, they generally aren't available and your only source would be to cannibalize another derailleur.

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    Senior Member sonatageek's Avatar
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    When I read the question I assumed the OP had the units in his possession and one or both where broken.

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    The cage takes up the slack in the chain on a chainring. The long cage is to take the slack in the chain on a triple between the small ring and the large chain ring; on a double, a short cage is used; compacts can use any combination though I find medium tend to work the best.

  11. #11
    coprolite fietsbob's Avatar
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    If so, how would I go about getting the parts for the changeover?
    There lies the issue.. I got an Olympus Campag short cage MTB from the mid 80's, in the late 80's ..
    and not long after, early in the 90's, got a long cage plate pair..
    .. fitted it on my Touring bike, Triple crank..
    26t [50t outer 24t granny] wrap needed..

    Campag, though, is (was) better about small parts than Shimano..

    I'd expect just getting the RD you need as a whole the path of least resistance..
    Last edited by fietsbob; 12-27-10 at 04:49 PM.

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    Quote Originally Posted by fietsbob View Post
    Campag, though, is (was) better about small parts than Shimano....
    Yeah, that reputation lingers despite it not having been correct (except for brifter repairs) for years.

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    bike whisperer Kimmo's Avatar
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    How many years? I got some derailleur bits... 10 years ago

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    Gear Combo Guru Chris_W's Avatar
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    Quote Originally Posted by Al1943 View Post
    Shimano does not offer a road derailleur with a medium cage, 105 derailleurs are either short or long. There are some Shimano medium cage mountain type derailleurs however.
    That is incorrect. Here's a quote direct from Shimano's own website about their 105 (road) rear derailleurs "The new derailleur is available in both short and medium cage lengths."

    Shimano calls the road RDs short and medium cages, and the MTB versions are medium or long cages. I believe the road medium cage and MTB medium cage are about the same length, which means that this naming system is useful because it is consistent, but I've never done a direct comparison between the MTB medium and road medium cages, so I can't verify this.
    Last edited by Chris_W; 12-28-10 at 03:07 AM.

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    Ride, Wrench, Swap, Race dddd's Avatar
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    There's no correlation as far as cage "lengths" between road and mtn derailers. Each size is specific to the application, each type is different.
    I.e., between XT and Ultegra there have always been 4 different cages (at least since 1996, and I'm not counting the Shadow models).

    They can be swapped about, I've done it, but can anyone confirm that the upper and lower (A and B) pivot springs are the same stiffness for all the different cages?
    If not, one would want to swap both springs to go with the particular cage being put into service.

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    Quote Originally Posted by Chris_W View Post
    That is incorrect. Here's a quote direct from Shimano's own website about their 105 (road) rear derailleurs "The new derailleur is available in both short and medium cage lengths."

    Shimano calls the road RDs short and medium cages, and the MTB versions are medium or long cages. I believe the road medium cage and MTB medium cage are about the same length, which means that this naming system is useful because it is consistent, but I've never done a direct comparison between the MTB medium and road medium cages, so I can't verify this.
    Ok, the 105 medium cage is a new design. Before Shimano road rear derailleurs have always been short and long, not medium. Campagnolo has had a medium for several years.
    Last edited by Al1943; 12-28-10 at 05:51 PM.

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    Habitual (Bike) Tweaker ATX 6Speed's Avatar
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    To answer everyone's questions I don't actually have another derailleur to work with. I did manage to order up the inner and outer plates from Shimano through my LBS. Once they get in I'll have the shop swap the plates and do some other work. As for the reasoning, there are a few reasons for doing it. Weight is a silly reason, but it would weigh a tiny bit less. I am removing the granny ring off of my triple front and don't really need such a long cage for my 12-26 cassette. Also, it would certainly look a lot nicer on there. Realistically these aren't huge reasons and there is no major benefit, but it does give me something to do.

  18. #18
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by ATX 6Speed View Post
    As for the reasoning, there are a few reasons for doing it. Weight is a silly reason, but it would weigh a tiny bit less. I am removing the granny ring off of my triple front and don't really need such a long cage for my 12-26 cassette. Also, it would certainly look a lot nicer on there. Realistically these aren't huge reasons and there is no major benefit, but it does give me something to do.
    Oh oh! Those are CBTD (Compulsive Bicycle Tinkerers Disorder) symptoms. There's no known cure so you might as well just go along and enjoy it. Don't ask me how I know.

    (FWIW, once I got the idea into my head I'm sure I would have done the same thing.)

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    Having a shorter cage is beneficial when using a compact crank as tension on the middle to small ring shift will be better when bouncing around on a trail lessening a chance of dropping the chain. That's my opinion anyways. Same reason applies for preventing chain slap on downhills while coasting.

  20. #20
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    Quote Originally Posted by ATX 6Speed View Post
    To answer everyone's questions I don't actually have another derailleur to work with. I did manage to order up the inner and outer plates from Shimano through my LBS. Once they get in I'll have the shop swap the plates and do some other work. As for the reasoning, there are a few reasons for doing it. Weight is a silly reason, but it would weigh a tiny bit less. I am removing the granny ring off of my triple front and don't really need such a long cage for my 12-26 cassette. Also, it would certainly look a lot nicer on there. Realistically these aren't huge reasons and there is no major benefit, but it does give me something to do.
    Well, to really look better a new derailleur would have done the job, and you could have done the work yourself.

    As to the weight, you are really getting obsessive. You might as well carry a tablespoon less water in your bottle as shave grams off with smaller side plates. Your speed would have increased immensely more if you had spent the time used on this forum, plus the time sourcing the parts, and the time you will spend traveling to and from the LBS with your bike in actually riding instead!

  21. #21
    Gear Combo Guru Chris_W's Avatar
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    Quote Originally Posted by Al1943 View Post
    Ok, the 105 medium cage is a new design. Before Shimano road rear derailleurs have always been short and long, not medium. Campagnolo has had a medium for several years.
    Not so "new" actually. My quote was about the 5700 series, but they used the same nomenclature for the 5600 series also (i.e., short and medium, not long). It does appear that this wasn't the case for the 5500 series, but that was discontinued 5 or 6 years ago.

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    Quote Originally Posted by Chris_W View Post
    Not so "new" actually. My quote was about the 5700 series, but they used the same nomenclature for the 5600 series also (i.e., short and medium, not long). It does appear that this wasn't the case for the 5500 series, but that was discontinued 5 or 6 years ago.
    This is interesting but also frustrating. The current Shimano "tech docs" show that the 5700 and 6700 RD's are either short or long, not medium: http://techdocs.shimano.com/media/te...9830702474.pdf
    What we need to know is what the real differences are in cage lengths and wrap capacity specs. I'm going to keep looking for this info.
    Thanks for pointing out that I may not be correct. I like to post accurate information but sometimes the manufacturers don't make that easy.
    The new 105 spec sheet shows the 5700 GS-S to have a capacity of 39 teeth, typical for a long cage RD and same as the Ultegra 6700. The 105 and Ultegra short cage RD's have capacities of 33 teeth typical for short cage RD's: http://bike.shimano.com/publish/cont...e-rd_road.html
    So what is the capacity of the medium cage? And where do we find the specs?
    Last edited by Al1943; 01-01-11 at 11:17 AM.

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