I’m changing the wheels on my CdF shortly to some Hope hubs and thought while I’m at it I might sort the gearing at the same time. I want to drop to a single ring up front but don’t know what to go for on the rear, I’ve seen most 10 speed road mechs only go upto a 32 cog so should I just go with a standard MTB mech (SLX?) so I can push it to a 36 (with the option of a 40/42 if needs be?).

A 10spd shimano mtb mech won’t work with Shimano Sti levers.

You’ll need to use a 9 speed shimano mtb rear mech, with the 10 speed shimano road shifters. You’ll be able to run a 36 cassette no issue, but 40/42 didn’t work for me (even with a long b-screw) as it always caught in the biggest cog

^^^thats what I’ve got on mine. 36 cassette, 9 speed mtb mech, 10 speed shifters.

Me too with 105 and SLX, and Rival, Apex mix on another.

Probably should have mentioned, I run flat bars with some standard Deore shifters currently so there’s no problem regarding shifter compatability!

One other thing, if I go 38 on the front will that be too light for general commuting duties?

One other thing, if I go 38 on the front will that be too light for general commuting duties?

Yeah, I’d say so. I’ve got a road double and my ‘easy’ sprocket is 42t, and that is too slow on anything vaguely downhill.

What have you got on there now? if it’s a standard double 39/52 see how you get on only using your inner ring.

I use 11-36 with a 42 ring and quite like it, 42×11 is ok on the road downhill or sprinting and I haven’t found much I couldn’t climb offroad. Lower than that might be annoying on road but if you stick to offroad or aren’t in a big hurry it’ll probably be fine. I’d be tempted to go for a 40T ring tho.

38×11 is still a higher gear than I have on any of my mountain bikes.

Yeah that’s my thinking, my Santa Cruz is running a 32 with 11/36 and I used to commute on that. The current setup is a 34/50 up front.