Looking to add some lower gears to a compact setup. Will a 9 speed mtb mech work with 10 speed road shifters and are the 10 speed cassettes the same for road and mtb? Ta

Yes for shifters. Road cassettes are 1mm narrower, Shimano alleged there were compatibility issues, but never seen any problems whatsoever. So, to all intents and purposes, yes.

AS njee says

I’ve done it and it works just fine – not even any snags at the extremes of the cassette (ran a bike 1×10 for a while, so used lots of either end)

My BIL just showed me his Dirty Disco with 105 10spd Brifters, Deore 9 speed non-shadow mech & 10spd 11-36 block. Worked a treat!

My BIL just showed me his Dirty Disco with 105 10spd Brifters, Deore 9 speed non-shadow mech & 10spd 11-36 block. Worked a treat!

Perfect! Thanks very much all. 😀

Works for me Geoff. I have an XT cassette on the tourer

and do I need a long cage if only running a double compact or can I get away with a medium cage?

Looking at this http://www.wiggle.co.uk/shimano-xt-m771-9-speed-rear-derailleur/ with an 11-36 block

Ta

Two people tonight have now used the term ‘brifters’. I insist that no one ever uses it again, horrendous term

Medium cage will be fine!

Medium cage only has a capacity of 35T, so long cage needed?
(50-34 plus 36-11 equals 41T)

Long cage it is then!

Arse, yes, sorry, I’m thinking MTB gaps. It would probably work, but I’d go long to be sure.

I’ve done it with a short cage but that was 11-32 so prob. best going long.

Sometimes it can over-shift very sightly, even with all stock items. Not sure why as sometimes it’s bob on. I’ve had to re-position the cable on the rear mech a few times to stop the overshifting, so just keep an eye out for that.

Ultegra 10sp STIs working with a 10sp 12-30 Ultegra cassette and a 9sp XTR medium cage rear mech on my CX bike, works fine.

Next thing is to try it with a 12-36 XT cassette for the Three Peaks.

Also, I agree with njee20 on use of the term “brifter”. Use of that demands immediate death by firing squad.