Would an XT front mech cope with a dual-ring setup: with a 22t inner and 40t outer? Obviously it's an 18t jump. This falls within the info on the shimano website which states a capacity of 22t, but that's spread across three rings, not two.

Any thoughts on whether I'm asking the front mech to do too much with an 18t jump?

If so, what's the largest tooth jump a front mech could cope with? I'm looking for dual-ring only, with the biggest middle ring I can manage.

Cheers

negatory

its a 14 tooth jump max really and even thats dubious … 12 is best for a nice smooth shift

it can be done 22:40 just dont expect clean reliable shifts in either direction and likely to drop chain off the inside.

26:38 and an 11:34 at the back = much better idea – 22tooth is a waste of space on an MTB – can walk quicker and use less effort

I used 22:38 for a bit, and it shifted OK, but the jump between them in terms of the size of the change in ratios was uncomfortable and difficult to adapt to. I went back to three rings in the end.

Thanks folks, I thought as much but just wanted it confirmed. Damnit.

I've got a pile of spare 22t inner rings (kit inventory last night produced 6 spare inner rings – how the hell did that happen?). I do find 22t too small most of the time but it would've been nice to find a use for them.

I think I'll try 26t-40t front set-up using my existing 32-11t cassette will be best at the moment, then replace the cassette with a 34-11t. I'm using 22t-34t at the moment but 34t is too small and I don't think 36t would be much improvement. I'm avoiding a 3-ring setup as I've got a dual-ring chain device fitted.

Oh, should say I'm used to big jumps between ratios and not having a particularly low lowest gear – I use an Alfine on a 29er and the easiest ratio isn't that easy…

22tooth is a waste of space on an MTB

TR, totally disagree. Granted that bottom gear with an 11-34 cassette is no quicker than walking, but stuff like Bhein a Bhuird, Carn Ban Mor, and even most of my local trails demand some time in bottom gear on a 22T. And not I'm not that unfit. I would argue that there is no point in anything bigger than a 36T

I am with CaptainMainwaring. I run 22/36 chainings. I use the 22 quite a lot. A lot is about style – do you like to turn a fast cadence climbing – if so the 22 is useful.

36 /11 top gear allows high 20s mph which is plenty for me offroad

I can't remember the exact calculations, but I also use an 8-speed Alfine hub with 23t sprocket and 32t chainring on a 29er (to further confuse things). IIRC this setup on a 26" wheel was equivalent to a 22t granny driving a 25t cog on the cassette. Basically i'm saying I manage fine with something a bit "tougher" than a 22t chainring for the riding I do, I must be more of a grinder than a spinner.

I find I never use the 44t outer ring but a 32t middle is too small, hence looking for a 2-ring compromise to allow a chain device too.

I'm going to try 26t-40t and see how I get on with my current 32-11 cassette.