Overdrive Magazine

June 2019

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34 | Overdrive | June 2019 E Q U I P M E N T W hat are the biggest fac- tors affecting your fuel economy? Engine inefficiencies are first, followed by aerodynamic drag. Then comes the rolling resistance of your tires. The biggest factor in that resistance, and the easiest and cheapest to address, is inflation. Imagine rolling two basketballs, one inflated correctly and one lacking pressure, says Tom Clauer, a senior manager with Yokohama Tire. "The one with the correct air pressure will roll much faster and further due to its [lower] rolling resistance," he says. So tires inflated to the recom- mended pressure should perform well. But if those tires are not designed for low rolling resistance, there could be more savings to grab by investing in tires built for that purpose. Tire makers achieve lower rolling resistance by manipulating features that include casing materials, rubber compounds and tread designs to sta- bilize ribs and blocks. These aspects affect the tires' tread depth, mileage range and traction. "A tire's tread can account for up to half of a tire's rolling resistance," says Mahesh Kavaturu, Goodyear's commercial technology director. LRR tires seek to reduce the amount of energy lost through tread deforma- tion, he says. "This can be achieved by reducing the tread block's height, by stabiliz- ing the tread elements using higher angle drafts, by designing the tread elements to take more rigid shapes or by increasing the surface area of the tread block to increase its stiffness," he says. Tire makers test rubber com- pounds for new products in part by evaluating "rebound." "Think of bouncing a rubber ball," Kavaturu says. "The higher the ball bounces, the less energy it has lost in its collision, or deformation, with the ground. Compounds with good rebound properties tend to exhibit lower rolling resistance." Weighing the tradeoff One widely held belief is that an LRR tire's lifespan is shorter than that of a standard tire. Mike Graber, Toyo's director of sales for commercial truck tires, says that is true only because the LRR tire usually is designed with less tread depth. The rubber itself doesn't actually wear measurably faster. "When measuring miles per 32nd of an inch of tread, the difference between the two is much closer," he says. "The deeper the tread blocks, the better the grip and wear, but the worse for fuel economy," says Sharon Cowart, product marketing direc- tor for Michelin North America. "However, through tire design, it is possible to utilize technologically advanced compounds and tire con- struction techniques to minimize a tire's rolling resistance while striving to maintain other performances. There are some design options avail- able that can lower the rolling resis- tance in areas not related to grip or other performances — internal com- ponents, for example." Customers who haven't tried LRR tires in years might be surprised at the improvements. E Q U I P M E N T E Q U I P M E N T The tread's deformation can cause half of a tire's rolling resistance, and LRR tires are designed to reduce that energy loss, according to Goodyear. Lifespans extended for fuel-saving tires BY JASON CANNON E Q U I P M E N T

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