Bigger = Better, IMHO. Currently running 29er 3.0 and 2.6 tires on the Karate Monkey. Big guy, full load, cushier ride. This summer my travels will see all kinds of riding surfaces, dirt, single track, dirt roads, gravel and pave. Last year I used the geax tattoo, a sort of slick that were 29 x 2.3, great tires.