Bridgestone expert puts the heat on rolling resistance

ERJ staff report (PR)

Manchester, UK - Up to around 20 percent of the fuel used by a vehicle is accounted for by energy consumed by tire deformation, friction with the road surface and air resistance, according to Keizo Akutagawa, general manager of materials development at Bridgestone Corp.

Of these energy-losses, 80-90 percent is due to rolling resistance as the tire deforms from a round to a flat shape as it contacts the road. It is, therefore, important to reduce energy loss in deformation, Akutagawa said in a keynote speech at the opening of the IRC RubberCon 2014 conference, held 14-15 May in Manchester.

“Everyone thinks tire is a nice round shape, but if you look at the contact area you see a round shape and a flat shape at the same time,” he explained. “The transition to a flat shape causes huge deformation of the tire rubber and is the main factor for tire rolling resistance.”

Reducing these losses, said Akutagawa, is now a top priority for Bridgestone Corp. as it seeks to operate more ‘in harmony with nature … and reduce Co2 emissions’ – in abidance with a corporate mission statement drawn up in 2011.

Using a series of advanced laboratory techniques, the Japanese tire maker has analysed the behaviour of the rubber compounds during deformation down to a molecular scale. These studies have identified the links between heat-energy losses and strain concentrations in areas where reinforcement particulates coalesce - even at relatively low strain levels within the rubber compound as a whole.

To illustrate the point, Akutagawa showed a video of tests in which cars fitted with different tires were rolled down a ramp from a truck. A test car riding on optimised low-rolling-resistance tires was seen to travel 43 percent further (85.4m. compared to 59.6m) than one fitted with conventional tires.

The improvement, said the Bridgestone expert, was due to the reduction in kinetic energy converted into heat by the deformation of the rubber.

(More details in the next issue of European Rubber Journal)