I have a 105 5700 50/34T chainset on my Cotic Escapade, with 105 10sp drop bar STIs and a 105 front mech.

I’m thinking about moving the XT M785 cranks across from my MTB and using something like the XT Trekking chainrings (come as 48/36/24T; I’d ditch the smallest).

The BB shell width of the Escapade is 68mm, whereas MTB ones are usually 73mm. Will I have any problems, or will my cunning plan work just fine?

What’s the actual gain? Making climbing harder and high speed sections slower? 🙄

road & mtb chainlines are different – would road front mech reach outer mtb ring? Hardly any gain apart from smaller jump between front rings i guess, try different chainrings on the road chainset instead?

your chainline will be about 5mm further to the right, which will make the chain run at a much larger angle in the middle and in particular outer ring in the mid-lower gears on the cassette.

The front mech might not have enough reach to go far enough across.

You can help (pretty much sort with a 68mm shell) with the chainline by putting all your BB spacers on the left hand side of the BB shell, but this may cause your right crank arm to foul the chainstay – all depends on the stay design.

Hang on, I’ve just realised you’re thinking about ditching the smallest ring on the xt cranks. What are you trying to achieve with this set up?

if you want smaller chainrings on your existing set up, just get some of these, you’ll have a lot less faff.

Outer:-
http://www.spacycles.co.uk/products.php?plid=m2b0s149p293

Inner:-
http://www.spacycles.co.uk/products.php?plid=m2b0s149p292

Oh dear – just to be clear…

I’m running a single ring on the XT crank (on my MTB) at the moment.

I’d like to know whether I can use it on my Escapade (road build), together with larger chainrings – as an alternative to buying a new 105 chainset?

If not, then that’s fine!

yes, you can, it’ll be a faff… but just buy those rings in the link I posted!