My current drive train is pretty much used up and needs replacement. I thought with this occasion, I could replace my curret drive train (2 chain rings, 10 speed cassette) with a singe chain ring and 11 speed cassette.

Currently I've got the following parts:

Chainset
Brand: Race Face
Type: Turbine
Sprocket 1: 26 Teeth
Sprocket 2: 36 Teeth

Cassette
Brand: Shimano
Type: Deore XT / CS-M8000
Ration chainring: 11-40 Teeth

I would like to get a single chain ring so I can remove a shifter and also gain more space to the ground. It did happen to me quite a few times that the larger chain ring caught a rock or a tree.

What size of chain ring (teeth) would I need so I'd have about the same transmission as with the current setup (especially regarding climbing)?

  • 3
    When going from 10 to 11 speed cassette you also need a new rear derailleur and shifter. – airace3 Dec 6 at 13:03
  • Yes I am aware of that. – Herr Derb Dec 6 at 13:05

Currently the gear ratio of your lowest gear is:

26/40 = 0.65

The Shimano XT cassette with the largest range is 11-46. To get the same lowest gear with this cassette you would need an chain ring with 46*0.65 = 29.9 teeth

You would need a 11-46 cassette and an chain ring with 30 teeth to get the same lowest gear with an 1x setup.

But your highest gear will be lower. At the moment the gear ratio of your highest gear is:

36/11 = 3.27

With the setup from above it would be:

30/11 = 2.73

This is approximately the same ration as the second largest gear you have at the moment with

36/13 = 2.77

  • 1
    If the OP changes everything anyway, he could also go with SRAM, where cassettes with a (slightly) bigger range are available, 10-42. Or the possibility of aftermarket cassettes with even more range (both Shimano and SRAM, although then no longer supported by the manufacturer's limits on derailleurs). – StefanS Dec 6 at 14:28
  • Yes I even had a look a the 9-46 cassette from e thirteen. But I'm a bit sceptical about this one. – Herr Derb Dec 6 at 15:30
  • Can always go to SRam Eagle at 1x12 - 10-50 – mattnz Dec 6 at 19:33
  • 1
    Fitting any of the Sram cassettes with a 10 tooth cog will require a new rear hub with XD driver, which will significantly impact the cost. NX Eagle (1×12) fits a standard freehub and has an 11-50 cassette which would widen the range a fair bit. – Carbon side up Dec 7 at 5:27

I am inferring (maybe incorrectly) that you already have the 11 speed cassette as an 11-40 and you are trying to keep your cost down. I (age 76) ride a fsr 29er with an 11 speed 11-40 and 30 tooth chainring. I can climb most mountain trails in the Phoenix area. My compromise is that my top end is about 15 mph. I don't care much, but, if I were to do it now. I would buy an 11-46 and use a 32 or 34 chainring. Be sure buy a narrow wide chainring like Raceface. Between the tension switch on your new Shimano m 8000 derailleur and the narrow wide chainring you won't need a chain retainer. If you are not trying to squeeze cost by using parts you already have, the previous answers are better than mine.

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