Note that the KH26 frame 2.5 is designed to accommodate a 2.3" to 2.5" tyre. Kris Holm says "My opinion is that there is a very good reason that modern Freeride and Downhill mountain bike tyres are in this size range - it is a very good balance between the competing demands of rolling efficiency, traction, and shock absorption. The same goes for an All Mountain unicycle; it really works well for both climbing and descending in this size. The wide rim gives a 2.3" - 2.5" tyre the stability of a much larger tyre without the extra weight."