Which rear mech for 42t 10-speed?

steve_sordy Posts: 2,441
edited September 2019 in MTB buying advice
I need a mech for an 11-42t cassette.
The Shimano M6000 Shadow Plus has been recommended and I looked it up and found this:
https://www.wiggle.co.uk/shimano-deore- ... P2EALw_wcB

It says Capacity : 41t (med GS version) and 43t (long SGS version)
Max large sprocket : 42t (med GS version) and 36t (long SGS version)

I can see that the long cage version would have a bigger capacity, but why does it not also deal with the larger sprocket? It looks like a typo to me, but long ago I learned that assuming does not always work in my favour.

I would have automatically bought the long cage version SGS, but now I'm not so sure. Advice anyone?


  • whyamihere
    whyamihere Posts: 7,686
    The geometry of the parallelogram and jockey wheels is different. You need the mech to move differently for a wide range cassette compared to a narrower range, so that it is both close enough to the small sprockets for good shifting and capable of clearing the large sprocket. This is the reason that Sram use an offset upper jockey wheel on their 1x systems, but they will not work with a front mech, while the Deore will.

    The cage length on the long cage just means it can take up more slack, so if you're running a triple, it can cope with the difference in chain length needed, and I assume they decided that not many people would be running a triple with an 11-42 cassette.
  • robertpb
    robertpb Posts: 1,866
    I think it's because Shimano can't even get their own website factually correct. If you look at the EU and USA sites there is a mix up in the information as they call both of those mechs 'medium' then refer to one as long, but if you go to other mechs info it doesn't add up between long and medium. Looks more like someone paste the wrong info in the wrong boxes.
    Now where's that "Get Out of Crash Free Card"
  • Thanks @whyamihere and @roberpb: It looks to me then that what I need is the medium cage GS.

    Would you agree with that?
  • whyamihere
    whyamihere Posts: 7,686
    Thanks @whyamihere and @roberpb: It looks to me then that what I need is the medium cage GS.

    Would you agree with that?
    Yes. What I should have mentioned in my last post is that I bought a medium cage M6000 for an old bike on 10 speed with an 11-42, and it worked perfectly.
  • Excellent!
  • Long cage is for doubles or triples but with a 11-34 or 36t cassette I think.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.