got a 38/24 on at the mo but would like to up the big ring to a 40 or 42. has anyone done this, not sure if a jump from the 28 to a 42 is too much an ask?

I have 28/42 on my sram cranks.

I’ve used a shimano mech and a sram mech.

I’m not sure this has any bearing.

But the sram chain rings are really expensive.

There is a 40-28 option I believe.

not sure if a jump from the 28 to a 42 is too much an ask

I run the standard 40/28 and it’s a noticeable difference but that’s to be expected. I usually crawl hurtle around in the 40t but if I have to make the shift to the little ring then it’s because I’m weak as piss the terrain requires it and the difference is exactly what the situation demands. It’s a bit like the debate over compact with road rings; some like it, some not so much.

Road mechs are definitely able to jump 14 as most chainsets are / were 39/53.
I’m fairly sure some of the hardcore hardtail Konas had a 22/36 combo a few years ago.

A 14 tooth difference is about the max recommended for mtb chainsets, I’ve got 24/38 no problem. I might try 26/40 as I need more speed! It’s not to say a bigger difference won’t shift though.

28/42 works well, used to run that years back.

Should be a go-er.

I had a middleburn Duo with unramped rings that would shift (more or less) OK at those sizes, so I’d imagine that a new XT mech and ramped chain rings would manage fine.

im running a dura ace FD so that should work, its for my cross 6 gravel / cross frankenbuild..

poh come to think of it, i have a XTR m970 3 ring crank in the garage, any one running these as a double – is it a case of just taking off the granny?

Fine. It’s only 14 t and a road compact is 16. Mine is used with a Campag compact front mech and works fine.

The 14t jump is fine. With a double specific front mechs I ran 36-22 on one bike and 38-24 on another. I tried a 38 22 on the Ibis as an experiment and ended up with only a whisker of chain rub/rattle by cross chaining it in the workstand, and probably only because the front mech was DM. I suspect a band-on on a straight tube would have been more tweakable.