Tire pressure, tire diameter, tire construction, tire tread and other factors all effect rolling resistance.
On smooth surfaces the higher the pressure, the less tire deformation and thus less rolling resistance. On rough surfaces (off road) the reverse is true. The lower the inflation pressure, the lower the rolling resistance. This applies on hard gravel roads and soft dirt tracks. Low pressure offers less resistance to adapting to the rough surface. By sinking into the ground less, the rotational mass handles the uneven surface more easily.
With tires at the same pressure, the wider tire will roll more easily than the narrow tire due to less deformation of the tire carcass. Smooth tread will roll easier than course treads, in part because of the tread giving a “rough road” effect. Also, simple logic tells us that it takes energy to make noise and course treads make noise.
While it is true that at equal pressure a wide tire will roll easier, racers use narrow tires because the narrow tire can be built to withstand more pressure than the wide tire. This combined with the lower rotational mass gives better performance for the racers needs.
Bottom line — For the recreational rider, a wider tire is more comfortable and nearly equal in speed to the hard riding narrow one.
source: “Schwalbe Tire Technical Info”
