For a loaded longtail cargo bike (Xtracycle FreeRadical) with 26" rims, what size tires would you use? 26x1.75 seems to be a pretty common size on a lot of the street tires I'm looking at, but I've seen a few 26x2.0 size tires as well. Seems regardless of the size the psi on most of these runs around 58 psi for the lower range up to about 70 psi on some models. Would the higher psi be better for a loaded cargo bike? I'd also be looking for tires with a decent tread, but not overly knobby, so maybe something like Continental Contact or Vittoria Randonneur. Opinions/suggestions?