Shimano 2011 XTR 2 X 10 > 1 X 10 conversion

[digit3]

I'm ordering up some parts for a new build. Getting my first geared bike in many years and have a few questions about the new XTR cranks. I want to run the new XC Race Crankset in a 1 X 10 set up using a 36T as my single ring along with an eThirteen XCX guide.

1. There are two different 2 X 10 offerings in XTR currently, the M980 and the M985. The M980 has 104 X 64 BCD which would allow me to chose from many aftermarket 36T rings. The M985 is the new 88 X 4 BCD pattern which would force me to custom order a ring. The M980 says "for Chain Line 46.8mm" and the M985 says "for Chain Line 49mm". What does this mean?

2. Going with the 2 X 10 cranks and converting them, I assume that I could choose either the outer or inner position for my 36T single ring depending on clearance from the chain stay. Anything else that I should be thinking of?

3. My plan is to go with 36T up front and 11-34 in the rear. Am I correct in going with the GS rear derailleur versus the SGS?

Thanks in advance!

[njee20]

If you're going 1x10 you should get the 11-36 cassette, if you're only gonna get the 11-34 why bother with the extra cost and weight of 10 speed, just go 1x9.

I've got a 36t ti 88mm BCD ring from Mathias Hellore, it's been excellent. Mounted in the outer ring position, not sure you'd get one on the inner ring position on many frames.

For simplicity I'd probably just get the M980 chainset though, you'll get decent money for the chainrings second hand, and can just buy any 104mm chainring to fit.

GS mech will be fine yes.

[digit3]

Thanks for your input.

I ordered the M980 2 X 10 with 104 bcd to allow for better chainring choices.

As to cassettes, the 11-34 has plenty of gear for me and will allow me to run less chain and hopefully have less slap than running a 36. With a 34T ring up front I'll have 1:1 for serious climbs.

[njee20]

But that totally defeats the point of 10 speed. You may save 1 chain link!

Get an 11-36 and either go for a 36t ring, keep your 1:1 bottom, and have a higher top gear, or stick with the 34t and enjoy a slightly lower gear. Or, save weight and money and get 9 speed...

[nitropowered]

With 10 speed, it is stupid not to go 11-36 when running single ring.

If you are worried about chainslap, get the Shadow Plus GS derailleur.

I am running XTR 980 shifter and the shadow plus rd, 38T front and 11-36 cassette. Works like a dream.