Originally Posted by seeker333

For 26" wheeled bikes, 26 x 1.4-1.8" tires usually work best for primarily paved surfaces. Anything smaller tends to wear out really fast; more than 1.8" seems to just add more rotating weight with no significant benefit. This obviously depends a great deal on the particular tire, but the good ones again are in the 1.5-1.75 range. Furthermore, most 26" bike frames/forks do not permit use of tires over 2".

Newer 27.5" wheeled bikes with >2" tires are likely better for non-pavement tours.