which size tires for RTW trip
 

what size tires are the easiest to get in places around the world 17" or 18" for the rear tire?

in Africa, I'd say 18" is easiest. the real issue is cross-section: I had to use a 110 section skinny hoop on the back of a well-laden XR650L

In southamerica i will guess 21´in the front and 18´at the back.Then 17´.
Pirelli,Metzeller and others then.Think of usd 100 for a set aprox.(MT)
Bye
KH

IMHO most of the developing world run around on 125's so skinny tyres for these beasts is all you can normally find, or at least in the less developed countries.