• 04-18-2015
    Shimano 10-speed rear derailleur with 9-speed cassette?
    Hey MTBR,

    My plan is to gradually (eventually) change my drive train from 3x9 to 2x10.

    I am wondering if it is possible to use a 10-speed rear derailleur with a 9-speed set-up.

    - 2014 Kona Prcept DL
    - Shimano CS-HG80 9-speed 11-34T Cassette
    - Shimano XT HG-93 9-speed chain
    - Shimano SLX RD-M662 9-speed Derailleur w/ Shadow
    - Shimano SLX Front Derailleur (don't remember the model at the moment)
    - Shimano Deore 3-speed, 22-33-44T, Crankset

    Will using something like...say...Shimano XT RD-M786 work with the current set-up? I am not sure if there is a different ratio between 10-speed and 9-speed.

    Any insight would be greatly appreciated!

  • 04-18-2015
    I thought sure there was a sticky for 9/10 speed compatibility...but sure enough I checked and it's not there.

    I think you'll find this does not work.

    Best of luck on your setup.
  • 04-18-2015
    9 and 10 speed derailleurs are not compatible, however 10 and 11 speed are, now that the XT M8000 group has been announced, you will have more options for your upgrade. It also looks like there are some aftermarket cassettes coming out soon to add to the mix. A 2x10 speed drivetrain using an 11 speed derailleur will give you more options when you buy it and down the road.
  • 04-18-2015
    There is no difference in performance between slx and xt for the rd anyway, just slight weight difference. I own both and a Shimano zee currently fitted. Rds ALL SHIFT THE SAME bit slx vs xt shifter, that you notice.

    But 10 speed rd not compatible with 9s shifter. Other way around works (not the smoothest shifting, very slight margin to get shifting right).

    If you feel you need an upgrade then just go 10speed. Not sure how many deals are left but over the winter you could go full xt for like $175. Shifters, rd (fd doesn't matter) and cassette (kmc chains that I use are $27 a piece as of last check)
  • 04-18-2015
    The break in compatibility is why my older bike is staying some manner of 9-speed until I can't get the parts anymore. Judging by availability of stuff to keep a 2x6 drivetrain running, I think I'm good until at least 2045.

    You pretty much have to bite the bullet on the shifters, rear derailleur, cassette and chain all at once. I've heard conflicting things about front shifting.
  • 04-18-2015

    Originally Posted by tigris99 View Post
    But 10 speed rd not compatible with 9s shifter. Other way around works (not the smoothest shifting, very slight margin to get shifting right).

    If that's your version of working I feel bad for your drive train.
  • 04-18-2015
    Worked fine for a year and a half. Shifted far better than anything I had previously owned. 9 speed slx rd and 10speed slx shifter. I say not smoothest because now I'm running xt shifter and zee rd and its smoother. But never access wear on chain, cassette or anything. And even my now xt/zee combo took a couple tries to get shifting perfect.
  • 04-19-2015
    Sounds unlikely - a 10 speed Shimano shifter pulls almost twice as much cable as a 9 speed shifter.
  • 04-24-2015
    Thanks for all the information from everyone! It looks like I'll have to do a full upgrade to switch to 2x10 (or 2x11).

    I'll definitely keep an eye out for any new and upcoming SLX / XT parts.
  • 04-29-2015
    Shimano 10-speed rear derailleur with 9-speed cassette?
    9 spd SRAM shifter and 10-spd Shimano rear derailleur, with 9 speed cassette works. Many have done it, including myself. The trick is a small spacer at the rear cable anchor point to tweak the ratio perfectly. (Works without it but not great). This only works since the 10-spd Shimano rear D has a ratio very close to a SRAM 9-spd rear D.