Does anyone understand the compatibility/running options for the new 2011 XTR drivetrain?

As far as I can tell, it's 10 speed only but with the option of a double or triple chainset. I presume the double will be the 'race' version set up and the triple will be the 'trail' version? If you want to move from a triple to a double do you then need to buy a new shifter as well?

Also, If I want to run any of the new stuff with the current 9 speed stuff I'm guessing I wont be able to, other than the front mech?

Is the trail and race stuff all cross compatible?

I read somewhere that a double trail version would be coming a bit later. That's all I know.

The shifters are the same for double and triple (with a switch to select the relevant set-up) The spacing for the chainrings is different to M970, and the cable pull is different. Unfortunately, everything pretty much needs to match (though i'm sure you could use dyna-sys XT or SLX chain and cassette). The only thing that puts me off, is the cranks are different for the different ring setups, so once you've chosen your ratios you're stuck. I fancy the 40/28, though it's not as pretty as the 38/26.

Much as shimano make good kit, they are right twunts for incompatability

I tried to get an old 9sp rear mech working with a new 10sp set-up and it just wasn't having any of it. The only bit that would work was the old front mech. Shimano now have loads of different mechs too, a move away from the universal ones. 🙁 Ones for double, ones for triple, E-type, it's a right nightmare.

Much as shimano make good kit, they are right twunts for incompatability

too true. Shimano's road stuff is full of sneaky gotchas between 9 and 10 speed, now we'll get the same with dynasplinge

Mainly compatible with a large wallet

Do the new 10spd cassettes fit on existing 9spd freehubs?

Compatibility is pretty easy for new XTR. The shifters do both 2×10 and 3×10, the only specific parts for 2×10 are the chainset and front mech.

All Shimano 10-speed Dyna-Sys cassettes fit on existing 9-speed freehubs.

The reason a 9-speed rear mech won't work with new 10-speed is that the cable pull is different.

mtbfix yes they do.

Much as shimano make good kit, they are right twunts for incompatability

The flip side of this of course, is that Shimano make stuff that's supposed to work together as a groupset…it's only us who try to bodge bits of this and that together, and the combinations are pretty endless, making everything compatible with everything else would be nigh on impossible.

Still, it is pretty annoying….

Not a hijack, but if I wanted to run XTR 10 speed shifters, 10 speed XT front and rear mechs and cassette, and an older 9 speed SLX crank – that'll be OK wouldn't it?

Ive heard that the big problem is going to be getting the cranks to fit so they dont hit the swingarm on most f/s bikes as the q factor is so narrow – my 2c wait till next year so they can get the bugs sorted out..

thebunk, I don't think so, aren't the 10 speed chains narrower? might not run on a 9 speed crankset.

thebunk – You can use 9 speed SLX cranks but should realy fit the Dyna-Sys chainrings as the ratios are different, as is the spacing between the chainrings due to the narrower chain.

RepacK – The 2x10s chainsets have a narrower q factor as they are designed mainly for XC hardtails. For FS bikes there is a 2×10 38-26 option which has the same q factor as the triple and M970 XTR chainsets.

What would the consequence be of running chainrings with the wrong rations and spacing?

It probably won't shift that well. if at all really.

The shifting won't be as good and there will be more torque placed on the freehub. Dyna-Sys is all about useable close ratio gears so using a 9-speed chainset won't really reap any benefit.