9 speed - 10 speed

morleyman200
morleyman200 Posts: 513
edited April 2012 in MTB workshop & tech
right im converting my current 2x9 to a 1x10, i'm buying new cranks, with suitable chainrings, i'm buying a new cassette and a chain and rear shifter. but i was thinking about the rear mech. I know people say buy a 10 speed one, but i've thought about it, and hear me out before you dismiss this, i was wondering if you could still use a 9spd one.

my thinking behind this, is the 10 and 9 spd cassettes are bother the same width (as they both fit on the same freehub) and isn't it the shifter which determines the size of the steps to change from sprocket to sprocket, so as the rear mech just simply moves up and down, wont this be the same as the 10 spd one function the same as the 9 spd one?

i know it sounds a bit stupid, but if i am wrong could you explain why

tom

Comments

  • styxd
    styxd Posts: 3,234
    You need a 10 speed one.
  • benpinnick
    benpinnick Posts: 4,148
    The angles on the mech are different to work with 10 speed (annoyingly). To go 10 speed you need new rear shifter, mech and cassette. Front mechs, shifters and chain sets are interoperable between 9 & 10 however.
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  • warpcow
    warpcow Posts: 1,448
    No, it's not just the shifter. The 'geometry' of the rear-mech is different too; e.g. the pivots are slightly differently placed to match the amount of cable pulled to the distance across the cassette.

    If your thinking was correct then SRAM mechs would work with Shimano shifters, and vice-versa.
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  • benpinnick
    benpinnick Posts: 4,148
    Oh, and I think the reason why is that shimano wanted to keep the throw (the amount the lever moves) the same for 9 & 10, so they had to change everything else to compensate, otherwise the 10 speed cassette would have been 1/9th wider than a 9.
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  • cooldad
    cooldad Posts: 32,599
    And make it fit on existing freehubs.
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  • The Rookie
    The Rookie Posts: 27,812
    Just to clarify, If you used a flat bar road shifter, then you can use your existing rear mech, no-one really understands (though you've had some guesses - I prefer they realised they would make more money this way) why Shimano then went and FUBAR'd it up for 10sp MTB stuff, as the road mechs are full compatable 8 to 9 to 10speed.
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  • njee20
    njee20 Posts: 9,613
    The Beginner is right. 9 speed MTB and 10 speed road stuff is interchangeable, so it can be done like that if you really want. The 10 speed Dynasis MTB shifters are nicer though, so I'd just do it and change your mech too.

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