Not full auto, just synchro for TT and why aren't you using 1x, anyways? Ha!

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wovebike.com | Wove on instagram

Only the 11-34 cassette requires a spacer and it's because it uses the XT/XTR style construction of having the biggest 3 (or 4?) cogs on a single carrier. The biggest cog actually hangs inboard of the shoulder of the XT/XTR freehub body. Road freehub bodies are wider, so you need a spacer to fill up that extra space.

That being said, yes, in theory you could do the same thing to fit a 12th cog, just hang it inboard of the shoulder. But then I think you would start getting dangerously close to the spokes. Kind of like how if you have a 10-speed freehub body, you can use the Edco Monobloc 11-speed cassette where the biggest cog sits inboard of the shoulder, but that cassette doesn't play nice with all wheels depending on were the spokes are.

I know sram says that the etap is only compatible with 11 speed, but is there any reason to think the RD couldn't be compatible with a 12 speed?? would that entail just a software update? or is there something about the function of the RD itself that would require a new one if sram went to 12 speed??

At some point in time the stepper motor and linkage would run out of travel. Did they put in enough physical travel for 12 speed....no idea. If the mechanism travels enough then it should just be a software update. The one thing to consider about all this is I think they added the 12 cog by getting closer to the centerline of rear wheel and using the room created by the spokes angling inwards to make room. This room doesn't exist for a smaller 12th gear....so if you are looking for a 11-32T or really anything less than a 50T, 12 speed cassette you aren't going to get it using this method.

I think pyrhana's response above was perfect ^

Shimano XT 11-40 11-speed cassette sits on a 10-speed hub. I think one more gear in there would be great! That 11-13 jump is brutal.

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/kj

http://kjmcawesome.tumblr.com/

This is Slowtwitch...you are supposed to correct me on some pedantic detail and in the process question basic engineering practices!!

I agree! I have my cx pit bike setup with a 44t front and an 11-40 rear. It's actually really nice gearing for general road riding and gravel riding. It's just that damn 11-13 jump! It makes it awkward in the 40-43 km/h range - where I seemingly spend more time than I thought. What I've started doing when riding that bike, is just using a higher cadence than I normally would in the 13t before I shift to the 11t so it doesn't feel like such a jump. This isn't always possible, but it's actually good cadence training when using this bike. I wouldn't be happy racing with that jump though.

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