XTR rear mech compatibility question.

qooqiiu
qooqiiu Posts: 212
edited October 2012 in MTB workshop & tech
Is the XTR rear derailleur - Shadow - RD-M980-SGS compatible with the XT crank FC-M780 42 - 32 - 24.

I'm looking to swap my XT rear mech for an XTR one. Why i ask is the XTR has a maximum capacity of 41 teeth and the one i currently have has a max of 43. AM i right in thinking il have issues if i change what i currently have?

Thank you.

Comments

  • Chunkers1980
    Chunkers1980 Posts: 8,035
    They are not directly related. You need capacity, which includes the rear too.
  • nicklouse
    nicklouse Posts: 50,675
    qooqiiu wrote:
    Is the XTR rear derailleur - Shadow - RD-M980-SGS compatible with the XT crank FC-M780 42 - 32 - 24.

    I'm looking to swap my XT rear mech for an XTR one. Why i ask is the XTR has a maximum capacity of 41 teeth and the one i currently have has a max of 43. AM i right in thinking il have issues if i change what i currently have?

    Thank you.
    all it is saying is that the max range it can cope with is 41 teeth. if your set up has a greater range you will have some gear combos that you can not use.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • cooldad
    cooldad Posts: 32,599
    It will work any any cassette up to 11/34 safely, although as you shouldn't be using big/big you can get away with more.
    Get it wrong though and you could rip the mech off.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • qooqiiu
    qooqiiu Posts: 212
    Basically what im asking is: i have this crank

    67199.jpg

    with this derailleur:

    67201.jpg

    but want to change it for this one:

    54861.jpg

    Will i have problems shifting?
  • qooqiiu
    qooqiiu Posts: 212
    i have a 11-36 cassette :(
  • nicklouse
    nicklouse Posts: 50,675
    and we can not answer your question as we have already said.

    the mech has a capacity of 41. what do you have?

    or do you not know what range is? or how to work it out?

    it is covered in the FAQs.

    or you could tell us what cassette you have. big and small cog sizes then we can work it out and tell you.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • nicklouse
    nicklouse Posts: 50,675
    whatmeansthecapacitymaizl5.jpg

    work it out
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • qooqiiu
    qooqiiu Posts: 212
    Crank is an XT 42 32 24
    Cassette is XT 11-36
  • The Rookie
    The Rookie Posts: 27,812
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    The Beginner wrote:
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.
    you miss the granny and big ring size :wink:

    for all gears he needs 43 range.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Chunkers1980
    Chunkers1980 Posts: 8,035
    The Beginner wrote:
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.

    Can't fault your maths. Should've gone to spec savers though.
  • The Rookie
    The Rookie Posts: 27,812
    Worked it out before he posted the 24 granny size .......
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    The Beginner wrote:
    Worked it out before he posted the 24 granny size .......
    before the first post :lol:
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    nicklouse wrote:
    The Beginner wrote:
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.
    you miss the granny and big ring size :wink:

    for all gears he needs 45 range.
    FTFY
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    The Beginner wrote:
    nicklouse wrote:
    The Beginner wrote:
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.
    you miss the granny and big ring size :wink:

    for all gears he needs 45 range.
    FTFY
    sure

    42-24 = 18
    36-11 = 25

    18+25 = ??
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Let me fill the ??.


    That is 43.... How many times can you be wrong before you give up.
  • cooldad
    cooldad Posts: 32,599
    The Beginner wrote:
    nicklouse wrote:
    The Beginner wrote:
    44-22 = 22 teeth at the crank, 36-11 = 25 teeth at the cassette, so 22+25=47 you'll need a rear mech with a capacity of 47 or more, 41 isn't going to work! You'll need to stay long cage.
    you miss the granny and big ring size :wink:

    for all gears he needs 45 range.
    FTFY
    Excellent. Keep digging.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • Chunkers1980
    Chunkers1980 Posts: 8,035
    Oh, and btw, there are a lot better ways to spank £150. Like shifters for example.
  • The Rookie
    The Rookie Posts: 27,812
    Oops, wasn't wearing my glasses and read the 42 as a 44 as in my sum - lesson, wear glasses more often!

    43 it is, still too much for a 41!
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • qooqiiu
    qooqiiu Posts: 212
    This bike has the shadow plus rear and a 42-32-24 up front so why cant i run that rear mech with the same 42-32-24 albeit an XT crank as opposed to an XTR featured on that bike?


    http://www.bmc-racing.com/fr-en/bikes/2 ... 9/xtr.html
  • nicklouse
    nicklouse Posts: 50,675
    qooqiiu wrote:
    This bike has the shadow plus rear and a 42-32-24 up front so why cant i run that rear mech with the same 42-32-24 albeit an XT crank as opposed to an XTR featured on that bike?


    http://www.bmc-racing.com/fr-en/bikes/2 ... 9/xtr.html
    like we have already said you can but you will not have use of all cog combos.

    either the chain is to short or the chain is too long the mech does not have the range to cope.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown

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