I am a casual rider. I don't race. My trails are single track with mixed pitches, sharp turns, logs and branches and lots of New england rocks (1-2 feet big) all over the place. 7 y ago I got a 29er (niner) and liked the better climbing (less bob). But I miss the tossability, huckability and agility of my older 26" wheeled stumpjumper. So I am going to try 27.5" wheels on my niner. I read a lot about people using wider tires in the front. - for example on their 29ers 2.6 and 2.5 in the front and 2.4 or 2.5 in the rear. On a 27.5" wheel I'd prob go up a bit in width.But what is the rationale of different tire widths?