Tire Makers Expect GHG Proposal to Boost Low-Resistance Model Sales
Federal regulators have taken steps to push the trucking industry toward greater adoption of low-rolling-resistance tires on trucks and trailers in the years ahead, but developing these increasingly efficient tires involves more than simply tweaking a rubber compound, manufacturers said.
Low-rolling-resistance, or LRR, tires likely would play a crucial role in meeting the Phase 2 greenhouse-gas standards proposed by the U.S. Environmental Protection Agency and the National Highway Traffic Safety Administration.
That proposal, issued in June, charts out increasingly stringent emission and fuel-economy standards for commercial vehicles — including tractors, trailers and severe-service and medium-duty trucks — from 2018 through 2027.
But creating tires to meet the demands of the various applications included under that proposal would require a lot of work from manufacturers, especially in the proposed rule’s later stages.
“Our engineers are constantly pushing the envelope and developing new technologies to make better products,” said Rick Phillips, vice president of truck tire sales for Yokohama Tire Corp. “I think we are definitely at the top of the learning curve, and the gains are sometimes subtle. But there is always room for improvement, and . . . we are dedicated to designing and manufacturing quality products and providing smart solutions to the industry.”
LRR tires, which EPA currently recommends under its SmartWay program, are designed to help fleets improve fuel economy by limiting the amount of rolling resistance they generate while traveling down the road.
Tire makers describe a process similar to baking, where research and development efforts hunt first for the ideal ingredients to blend with rubber and then switch to the optimal process for curing and assembling the finished tires. Manufacturers guard their finished recipes zealously and speak of them only in general terms.
“Curing the rubber at high temperatures and [quickly] leads to high-rolling-resistance tires,” said Brian Buckham, general manager of commercial tire marketing for Goodyear Tire & Rubber Co. in Akron, Ohio. “Curing at lower temperatures and slowly is better for low rolling resistance. You have to optimize a big system,” Buckham said of the design challenge.
Calculating just how thrifty the tires can be is hard to quantify because of all of the variables involved among fleets, Buckham said. However, the Goodyear website does have a savings calculator that allows fleet managers to develop an estimate based on the particulars of a given carrier’s operations.
Madhura Rajapakshe, a test engineer with Smithers Rapra Technology Ltd., an Akron-based materials testing firm, said that there are varying degrees of rolling resistance for different tire positions. Trailer tires can work well with the least rolling resistance. Steer and drive tires, however, still can be considered LRR, even when they have much more resistance than a trailer tire. Trailer tires can trade off traction considerations for less rolling resistance, but steer and drive tires cannot.
Indeed, while wheels naturally are inclined to roll, scientists and engineers have invested a lot of time studying what keeps them from rolling farther. For truck tires, deformation from weight is a big factor.
Load up 18 inflated tires with a total of a tractor-trailer’s allowed weight of 80,000 pounds (more than 4,400 pounds per tire, on average) and the shape changes, wasting energy in the process.
“If a tire is underinflated, rolling resistance increases, which means it takes more energy to roll it along,” said Gary Schroeder, a sales director for Cooper Tires, including its Roadmaster brand.
“EPA estimates that if all the tires on an 18-wheeler are underinflated by 10 pounds per square inch, fuel consumption increases 1%. This is the reason that the Phase 2 proposed rule contains references to automatic tire-inflation systems and tire-pressure monitoring systems,” Schroeder said.
Heat also is an enemy of LRR tires. When energy turns to heat rather than propulsion, it’s wasted.
“You want to dissipate heat more efficiently, and you don’t want to generate as much heat in the first place,” said Walter Weller, vice president of sales for Double Coin Tires.
“We search for cooler-running compounds,” Weller said, adding that LRR tires make up about 25% of Double Coin’s current sales in U.S. and Canadian heavy-duty truck and trailer tires.
The emission and efficiency standards that EPA and NHTSA propose could prove difficult for tire makers and their fleet customers in the outer years, said Glen Kedzie, energy and environmental affairs counsel for American Trucking Associations.
The tire section of the massive proposal is complicated, Kedzie said. There are standards for several types of trailers and several types of trucks, and the standards will change during the proposed rollout period of 2018 through 2027.
“We have lots of concerns about tires,” Kedzie said. “Are the anticipated costs correct? What will the wear characteristics be like? How will they perform on retreadability, and safety and braking? We have far more unanswered questions than answered questions.”
EPA measures rolling resistance in terms of kilograms of force to be overcome per metric ton of load. Like a golf score, lower numbers are better, and the numbers get lower over time. Kedzie said he has worries about whether the manufacturers can develop tires that will meet the 2027 proposals by that date.
All tire makers contacted for this story said they have research and development departments working on design and manufacturing improvements.
Paul Crehan, the director of product marketing for Michelin Truck Tires, described the company’s LRR tires as “benchmark products in the balance between tread wear, scrub resistance, traction and durability at the best possible rolling-resistance level.” He said Michelin offers more than 50 steer, drive and trailer tires with low rolling resistance, and it is the company’s fastest-growing truck tire segment.
“The combination of tread life and fuel efficiency, while maintaining our commitment to safety, is a key pillar of environmental impact by reducing carbon dioxide emissions, fuel consumption and waste of tires with tread life,” Crehan said.
Bridgestone Americas Inc. is eager to work with regulators and legislators on the standards, said Matt Loos, a marketing director for the tire maker.
“We try to anticipate those moves and want to stay ahead of them,” Loos said.
However, tire makers are simultaneously grappling with another challenge — fleet acceptance.
While there is little question about the desirability of saving on fuel spending or that LRR tires help with that, the tires have posed conflicts with two other prized qualities: traction and durability.
Goodyear’s Buckham said tire engineers work on the triangle of fuel mileage, traction and durability. He said that it is easy to improve one or two of those points significantly by curtailing a third but noted that is a poor strategy. Rather, Buckham said, Goodyear works to maintain all three points through innovations in rubber compounds and tread and casing designs.
R.E. West Transportation, a truckload carrier based in Ashland City, Tennessee, puts LRR tires on its 130 power units and is sufficiently concerned with vehicle mileage that it has used Smithers Rapra for testing, said maintenance manager Dustin Stricker.
The LRRs require more maintenance, he said.
“Traction is high, but we did lose a little in tread life,” Stricker said of the switch to LRR. “You really have to pay attention and rotate your tires more.” West’s technicians move the tires left and right, forward and backward, and check inflation scrupulously with automated systems, he said.
West trades in tractors after 500,000 miles, Stricker said. Shortly after switching to LRR tires, he was using 3 to 3½ sets of tires for a 500,000-mile life. With the addition of some new maintenance procedures, Stricker got that down to two sets of LRR tires per 500,000 miles.
Despite the extra work, “the fuel-mileage gain overrules everything else,” Stricker said.
Smithers Rapra’s Rajapakshe said tire makers have gone through a lot of innovation to find a “sweet spot” where mileage, durability and traction are reasonably well-balanced.
Despite manufacturers’ research and development efforts, truck tires probably will never catch up with the current railroad wheel. Steel wheels on steel track endure only the most minute levels of wheel deformation.
“Even the lowest-rolling-resistance truck tire has 10 times the rolling resistance of a railroad wheel,” Rajapakshe said.
With 240 U.S. locations, the TravelCenters of America-Petro chain of truck stops provides a good perch for watching fleet preferences on tires, said Gene Kanzigg, the chain’s tire program manager. Fleets don’t organize their tire purchases around truck stops, he said, but they do buy a lot of replacement tires there in the event of blowouts.
“SmartWay-verified tires are of high importance, especially to larger fleets and in California. We’ve moved toward SmartWay-verified tires because the market has driven us,” Kanzigg said.
But unless someone is a tire professional, LRR tires look like any other.
“They’re black and round; you can’t tell the difference just by sight,” Kanzigg said.
Easier to spot is tread depth. Kanzigg said a full inch used to be common on tires and that it made for longer wear — but at the cost of higher rolling resistance and a decrease in fuel mileage. New LRR tires start with much less tread depth.
Bridgestone’s Loos said an LRR trailer tire is about 12/32 of an inch, a steer tire about 20/32 and a drive tire 28/32.
