I am upgrading (or downgrading ? :P) my MTB to 1x, currently on compact 2x10.

I will be changing chainring, derailleur and cassette. I will get 11-42 Sunrace MS3 10-Speed Cassette. Also Shimano XT M8000 Shadow+ 11 Speed Rear Mech

I will be using the mech with 10 speed shifter, I read and was told on multiple places they work better than 10speed mechs with the large cogs.

What I don't know yet is if I should go for long or medium cage? Im on a hardtail

  • Generally, the length of the cage on the rear derailleur is governed by the number of teeth on the largest cog of the cassette. You then need to look at the spec of the derailleur you want to fit.
    – PeteH
    Jul 16, 2016 at 7:51
  • Looking at shimano I cant see mention of cage size. bike.shimano.com/content/sac-bike/en/home/components11/mountain/…
    – Giannis
    Jul 16, 2016 at 8:08
  • no, they gave their site the "marketing treatment" a year or 18 months ago. It has a lot less useful information now. Certainly you can deduce that the range of that particular derailleur is 11-42T. But it's not clear from that page whether that derailleur even ships with cage options.
    – PeteH
    Jul 16, 2016 at 8:20
  • 1
    Personally I'd try it out with whatever you already own. This costs nothing more than time. Then if it doesn't work you know you need to buy something else.
    – Criggie
    Jul 16, 2016 at 8:40
  • I am looking to buy now, it looks like I most likely want medium, just wanted a second opinion :)
    – Giannis
    Jul 16, 2016 at 8:42

1 Answer 1


For 1 by X, a medium cage has enough capacity (11-42 needs only 31).

Refer here for details of compatibility between different drive line equipment.

Using an 11 speed derailleur with a ratio of 1.1 vs 10 speed is 1.2, with a cable pull of 3.4mm, across 9 shifts, gives an error of 3mm. If you have have the derailleur perfect in the center, you are out by 1.5mm at the outer cogs, which is getting to be a little far out for my liking. Many say it works, but I have seen no one report back after the chain, cassette and cables are no longer new and shiny and in perfect working order. However, I have also heard and suspect it to be true, that the M8000 provides a better 10 speed 11-42 setup than a 10 Speed derailleur.

Better alternates to the M8000 if you don't want to go to 11 speed are third party upgrades to your 10 speed derailleur, e.g. Rad Cage, Goatlink, or both.

I looked at going 1x for my 3x10, and decided it was either go the whole hog and do it properly with 1x11 or stick with what I had.

  • Great answer. I think I will be trying how it works with 10spd, and if I have problems I can sell the cassette and go for 11spd shift/cassette /chain
    – Giannis
    Jul 16, 2016 at 9:40
  • I used an 11sp M8000 with a 10sp Sunrace cassette and 10sp XTR shifter and it worked brilliantly for 600km until I decided to go 11sp. Just set the limit screw on the mech
    – Adam Hey
    Aug 5, 2021 at 13:04

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