i've been riding thailand, cambodia, vietnam, laos, southwest china on and off for the past five years.
h'bar bag at 5 pounds, 30L panniers with about 20-25 pounds, and my 185 pounds. usually running
26*1.75, kenda or cheng shin or local no-name. if shoulder profile and raised center bead, then no
problems. paved, dirt, cobbles, floods, landslides, jungle. i wouldn't be comfortable on 1.5's