About to change drive train to a 2 chain-ring set up, using a 40/28 combination and a 36-11 rear cassette. Has anyone run a short cage on this set up? Rear mech capacity appears to be 35, but that set up is 37 so it s going to be close.

Medium cage?

In my experience (running 2×9 22/34 chainrings and 34t cassettes) it’s best to use a medium cage mech with a few chain links removed. A 2 x 10 set up would also allow a clutch mech to be used to keep things nice and tight.

ive just changed mech on a 36/ 22 and 11-34 2×9 set up. I used a medium cage (GS) Saint mech and it only just had enough capacity to take up all the chain

Well, technically its a meduim cage, but shimano designate long cage (SGS) or short cage (GS). Long cage is 48 capacity, but i like the idea of running a short cage if i can.

Rear mech capacity appears to be 35, but that set up is 37 so it s going to be close.

If it’s a FS factor in the swing arm movement as well.

Have a short cage X9 on the big bike with a 36T & 11-28 cassette. The mech would be toast with an 11-34 cassette. The same mech works fine on the jump bike.

I think the issue with the short cage is how close the derailleur gets to the cassette, I think they would touch with that size cassette.

I think the issue with the short cage is how close the derailleur gets to the cassette, I think they would touch with that size cassette.

Nope, GS and SGS are both rated to the same largest cassette sprocket size. The cage length only affects the length of chain the mech can cope with.

Fair enough, everyday is a school day! 😉