The “rolling resistance” of a tire is defined as the physical drag a tire exhibits while in motion (rolling). This drag is measured as a force. Obviously, the more drag, the more fuel used.
In the average truck tire, for every 1% improvement in rolling resistance or reduction in force, a one-third % improvement is realized in fuel economy.
Truck tires are made up of many components, including “steel” cord in many areas. The steel cord, though, has an insignificant contribution to rolling resistance as compared to the rubber components – in particular the tread area.
It should be no surprise that when it come to improving the tire for better fuel economy, tire engineers focus heavily on the tread area which contributes 50% to 60% of the rolling resistance on the average truck tire. But engineers must make sure they manage improvements in rolling resistance without affecting the other performance characteristics of the tread area, including wear rates and irregular wear fighting capabilities.
Our engineers are doing a great job in reducing rolling resistance . . . as evidenced by the performance of Double Coin TBR tires against Michelin and Continental in an independent test. Click here for test results.
The Double Coin OptiGreen™ series of SmartWay® tires features a total of eight product lines, including the FR605 steer tire, FD405 drive tire and the FT105 trailer tire. We also have two super wide tires in the Optigreen line-up -- the FT125 super wide trailer tire and FD425 super wide drive tire. All of the OptiGreen tires are SmartWay verified, meaning that they have met the EPA's requirements for low rolling resistance.
Below are some key definitions of the key factors affecting rolling resistance in tires:
Tread Compounds: Low Hysteresis Rubber is more resilient than High Hysteresis Rubber. Hysteresis is the difference between the amount of energy absorbed when a rubber is stretched and the amount of energy released when the rubber is relaxed. High Hysteresis indicates a high loss of energy and so is it is good for energy absorbing applications. Using a Low Hysteresis compound will contribute significantly to lowering the rolling resistance of a tire.
Tire Inflation: If a tire has too low of an inflation pressure for a given wheel load, it results in greater sidewall distortion or tire deflection as we call it. With poorly inflated tires, the more distortion experienced in the sidewall, footprint or contact area (area of tread touching the road), the more heat and energy are generated. As heat or energy increases, the tire becomes less efficient for rolling resistance.
Tread Design: The less disruption a tread design offers to the direction of rotation, the less heat buildup. As stated before, heat and energy make a tire less fuel efficient. More modern fuel efficient tread designs and compounds are trending towards using ribbed grooves, narrower grooves widths and fewer grooves to reduce this disruption.
The quest for lowering the rolling resistance in tires is ever evolving; who knows where the future will take us in compounding, computer optimized tread designs and so on. One thing’s for sure – the engineers involved with the Double Coin tire brand will always be pushing the envelope.