OP, funny you should mention 27" wheels, touring, and lack of available parts should things go sideways like they did on my last tour. blew all my tubes and ended up riding on a flat for a few miles, like seven, before i remembered the tire was a 27" and i might have a devil of a time finding a new tire if i ruined it. so i walked (thank god for MTB shoes) the last six miles to Hayfork, Ca. they had one pitiful hardware store. no presta valve tubes, but to my surprise the only narrow (like 28mm) tire was a 27".
and to think i could have ridden the flat all the way into town rather than suffering the humiliation of having to walk!
