Originally Posted by
jayr
Bike originally came with 700x28c and I didn't notice much difference in rolling resistance going up to 32 but the ride improved immensely.
Thats probably because wider tires have less rolling resistance than narrow ones, all other things being equal. Of course, all other things are usually not equal, and rolling resistance is only a small part of the total drag on a bike once you are at speed, but simply switching to wider tires will almost definitely not significantly increase rolling resistance.
From
http://www.schwalbetires.com/tech_in...ing_resistance:
Why do wide tires roll better than narrow ones?
The answer to this question lies in tire deflection. Each tire is flattened a little under load. This creates a flat contact area.
At the same tire pressure, a wide and a narrow tire have the same contact area. A wide tire is flattened over its width whereas a narrow tire has a slimmer but longer contact area.
The flattened area can be considered as a counterweight to tire rotation. Because of the longer flattened area of the narrow tire, the wheel loses more of its "roundness" and produces more deformation during rotation. However, in the wide tire, the radial length of the flattened area is shorter, making the tire "rounder" and so it rolls better.