"In the real world...  We have instrumentation to measure rolling resistance, there are limits of coarse but a wider tire at the same PSI will have LESS rolling resistance than a narrow tire because the tire will deform less....The reason you see all these narrow tires is NOT because of function, its for funding road racing. The reason they use narrow tires is to aerodynamically shave off tenths of a second... Narrow tires have zero purpose on an everyday commuter bike or something to cruise around on.."