So, trying to use some 10 speed double chainrings (28-40) with an otherwise 9 speed set up (it was a triple up front).

I have:-

9 speed SLX shifters
9 speed Xt cassette
9 speed xt shadow rear mech

I want to run 40-28 double on the front (the rings fit to my xt 9spd triple crankset just fine). My old triple mech fouls the rings and gives other issues, so i installed a double front mech.

I have a 9speed KMC chain which is now catching on the 40t outer ring pick up pins in the top three sprockets.

A chimano HGX 10speed chain is narrower and I assume doesn’t catch on these pins…

So, the question after that pre-amble is….

Can I run a 10speed HGX chain through a 9 speed mech and cassette??!

Has anyone tried this? Will another 10speed chain (i.e. KMC work? actually I could try that tonight with one off the road bike)

I’ve run kmc 10sp chains on 9sp gear before, no probs

Yes it’s fine.

Sorry to hijack but I am doing something v. similar. What do you do about the front gear shifter, which I presume is a triple SLX? Do you just have a redundant position and stop chain jumping off using the limit screws? Or is there someway of altering internals on a left shifter? I did delve into one when it broke but couldn’t do any thing with it.

I just use the limit screw – so I effectively only use the lowest two positions of the shifter. You physically can’t move the shifter into the 3rd position.

Works great. I do it on the road bike too – triple sti with a double front mech and chainset – it’s actually how one of the bikes came set up from new.