Looking at some of his later pics (I have been following his trip on flickr), it looks like he uses WTB Nano Raptors. I run them on my Fargo, and they seem to be a decent tire for mixed terrain; they won't make you walk too often because of lack of tread, but the center is fairly constantly treaded, which makes for a faster rolling knobby. Not my choice for a road-only route, but for his trip, they are an excellent choice.