current setup is Shimano M-615 SGS rear derailleur, Shimano Deore M591 shifter and Shimano CS-HG81-10 11-36T cassette

My idea is to return to 9-speed while not throwing the derailleur. Wanna change the shifter to SunRace M95 (9sp shimano compatible, dunno if pull ratio should be changed to be DynaSys compatible) and some 9sp cassette with alu spider (the hub has alu freewheel body) or at least to remove one of the cogs.

Any ideas if the 9sp shifter will work with the 10sp derailleur? Thanks in advance

  • Why do you want to do this?
    – Batman
    Commented Jul 4, 2017 at 19:41
  • -1 cog lowers weight on rear, -1 cog gives me more centered median gear, some 9sp shifters are a lot better than 10sp ones, 9sp chains are way more durable than 10sp (have >40k km on 9sp and another 10k on 10sp - 10sp chain is too worn than 9sp chain) ... otoh 9sp chain is somewhat heavier than 10sp
    – 1000Gbps
    Commented Jul 4, 2017 at 19:56
  • 3
    The weight differences will be washed out by your lunch. If you don't like your current cassette you can pick a different one with better spacing or whatever for your riding style. Ditto for the shifters -- there are bad 9 speed shifters as well (though I'd think the Deore ones are fine). Even if you perfectly maintained a chain, I would think a chain used for 40000 km is way beyond worn out. You might get a few more miles out of a 9 speed chain, but not that many.
    – Batman
    Commented Jul 4, 2017 at 20:02

1 Answer 1


Shimano 9 and 10 speed mountain stuff have different cable pulls.

So, if you want to use a Shimano 10 speed mountain derailleur in a Shimano 9 speed setup (i.e. 9 speed shifter + cassette) you either need to:

  • Buy a friction shifter, which obviously doesn't care about the speeds

  • Buy a device which can change the cable pull appropriately (in this case, a JTek Shiftmate 6 would work) and use a Shimano-compatible 9 speed shifter. Note that this will likely cost more than the 9 speed derailleur.

10 speed cassettes in a 9 speed system introduce another level of complication since the cogs are a different distance apart, and would require a different adjustment to cable pull. It'd be like you cascaded a JTek Shiftmate 2 and 6.

  • Great but I don't see the price of Shiftmate 6
    – 1000Gbps
    Commented Jul 4, 2017 at 20:01
  • Find a retailer in your country and see what it is -- it's a niche product, so not many people carry it, but expect to pay something between 35 and 60 USD. Some retailers (e.g. SJS Cycles in the UK) ship internationally, which might save you some money if you're not there.
    – Batman
    Commented Jul 4, 2017 at 20:08
  • 1
    Note that the cost of the Shiftmate likely exceeds the cost of your favorite 9 speed derailleur.
    – Batman
    Commented Jul 4, 2017 at 20:17
  • I know but the idea to transplant a clutch and stronger coil on 9sp Alivio is still on the drawing board
    – 1000Gbps
    Commented Jul 5, 2017 at 19:39

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