mixing road and mtb components?
 

I have a CX bike that I plan on take touring. I have equiped it with rack and fenders and bar-end friction shifters. Currently I think the gearing is a bit high and I mostly use the small ring in the front. I have a 9-speed XT rear mech that I am not using. My question is, will there be any problem if I change to a 9-speed cassette with with large cogs in the read and use the xt mech (it is currently all 10-speed shimano 105)? I guess I have to change the chain as well but apart from thet is there something I should think about?

Cheers,

Claes

No problem. If it is a rapid rise derailleur it will reverse the direction of the bar end shifter's action.

Aren't the 9 speed cassette sprockets spaced wider than 10 speed?

The OP says the shifters are friction, so cog spacing doesn't matter.