How low can you go? Operators must weigh pros and cons of low rolling resistance tyres

Rolling resistance in tyres is largely the result of three factors – aerodynamic drag, road friction, and internal friction (also known as hysteresis of materials, which in this case is the rubber in the tyre). The latter is responsible for up to 95% of energy losses, and refers to deformation of the rubber as it meets the road and flattens slightly under the weight of the vehicle and morphs to fit the surface of the road.

The tyre, an elastic material, is continuously changing shape, which requires energy. Some of this is recuperated when a section of the tyre reverts back to its normal shape, but the rest dissipates, released as heat energy. On a heavy-duty truck, which typically has 18 wheels, these losses add up – according to the North American Council for Freight Efficiency (NACFE), rolling resistance costs a Class 8 or above truck around US$0.21 per mile, equating to around 30% of total fuel cost.