He adds that the M157 also deploys a four steel-belt package to ensure uniform growth of the tread area. “This design reduces rolling resistance while also helping to reduce irregular wear; the result is an improvement in fuel mileage.”
According to Tim Miller, Goodyear’s customer marketing manager-Commercial Tire Systems, other examples of mpg-oriented tires are within Goodyear’s Fuel Max line, including these models: G316 LHT, G572 LHD, G662 RSA, G305AT LHD, G392 SSD, and G394 SST. “Goodyear’s Fuel Max Technology incorporates cool-running compounds and construction to help reduce truck fuel consumption,” he remarks. “Goodyear also offers retreaded tires with Fuel Max Technology.”
“Tires today are much more fuel-efficient than they were just a few years ago and as technology evolves, this will improve even further,” contends Yokohama’s Phillips.
“Currently, tires actually play a relatively small role in fuel efficiency when compared to the engine and aerodynamics,” he adds. “But as vehicle manufacturers continue to improve on those factors, tires will play a larger role. So the engineering will continue to be a work in progress.”
As to whether fleet owners should be concerned that the harder push now on for tire/retread mpg gains might lead to trade-offs in durability and retreadability, Double Coin’s Murphy says there’s no doubt that’s a consideration when any manufacturer modifies its products.
“The durability/retreadability can’t suffer due to these mpg/GHG requirements or the overall tire costs to a fleet will increase,” he continues. “The key for us is to optimize all aspects of the tire’s functionality and performance so that the lifecycle costs of a Double Coin tire continue to be attractive to the end user.”
Yokohama’s Phillips points out that “typically, fuel-efficient tires run cooler than non-fuel-efficient tires so the cooler operating temperature actually helps prevent casing fatigue. This in turn helps the retreadability and durability of the tire.
“However,” he continues, “there are certainly other trade-offs for fuel efficiency. Fortunately, engineers have several ways to lower the rolling resistance in a tire. So depending on how the product is designed and manufactured, you may notice a little less mileage or a little less resistance to cuts and snags. The challenge is to utilize all the tire’s components in a way that deliver the expected fuel efficiency without compromising the total performance of the tire and its intended application.”
Continental’s Stansbie recommends that tire buyers continue to “pay close attention to what tire makers offer to ensure expected tread life and retreadability within the parameters for low rolling resistance.”
Phillips says Yokohama’s approach to the mpg/lifecycle trade-off is to “combine different elements of the tread, the rubber compound, the casing, and also the manufacturing process to deliver fuel efficiency as well as other performance standards.
“A common way to lower rolling resistance is simply to shallow the tread design,” he adds. “However, we were able to design and produce the 703ZL drive tire at 32/32 [tread depth] with low enough rolling resistance to be verified by EPA as a fuel-efficient product. It’s currently the deepest tread depth on the EPA list of verified products.”
Double Coin’s Murphy says the GHG rules being imposed on truck OEMs are creating further impetus for lowering the rolling resistance of tires. “Double Coin is not only now providing EPA SmartWay-verified tires for those users that participate in the program, but we’re also reviewing all tires in our lineup for rolling resistance. Our goal is to lower these values on core products such that we can assist OEMs to meet the new [GHG] guidelines.
“Some products we supply already meet the [GHG] guidelines, and we’re continuing to work on others to reduce the rolling resistance,” he adds. “It’s an ongoing process that utilizes technology in tread patterns, casing components, rubber compounds, and a myriad of technical developments.”
Michelin’s Crehan says that to meet the specifics of the federal GHG category for heavy-duty trucks, there are six approaches OEMs can access to meet the targets. These are aerodynamics, weight reduction, extended idle shutdown (such as via APUs), speed limiting, and drive- and steer-axle tires with low rolling resistance.
“Selecting from these choices, the OEMs can make various adjustments to meet the heavy-duty GHG goals,” he explains. “For vocational trucks, though, only the steer and drive tires will matter, as those vehicles are not running fast nor do they have persons sleeping in them.”
Crehan notes that Michelin’s “general position” on both the SmartWay program and the CARB and GHG rules is positive. “Environmental sustainability and fuel efficiency are the targets and that is being well communicated to the trucking marketplace.”
Closing the loop
Bridgestone’s Walenga reports that the tire maker has been working with truck OEMs it supplies for the past three to four months to get them the tire data they will need for their GHG calculations.
“The way it’s working is that if an OEM expects to use a particular tire on a certain truck, they need average rolling resistance quotients from us,” he explains. “And they need that data for each and every tire model they will buy. As it happens, our line of tires that are SmartWay-verified will handle most of the expected truck applications under the GHG rules.”
Along with his contention that the advent of SmartWay-verified retreads will help close the mpg loop, Walenga says the positive upshot of the GHG rule will be “more fleets ending up with more fuel-efficient tires on their new trucks. From there, more fuel-efficient tires will get out into the marketplace. And fleets will be wise to buy replacement tires and/or retreads that are fuel-efficient to keep the mpg gains going for them.”
“In the replacement market,” he continues, “there are many applications where the need for verified technology is not mandatory due to applications or other requirements. I will say that both power unit and trailer OEMs are focusing heavily on the SmartWay-verified technology products at this time. Fleets and other end users seem to be turning towards products that can help their bottom line and lower costs.”
Yokohama’s Phillips says that fuel-efficient tires have “absolutely” become a de facto standard spec at many fleets. He says the truck’s application helps determine the need for fuel efficiency, “but for most linehaul and many regional operations, fuel efficiency plays a major role.”
“There’s always a risk involved when buyers feel forced to do something,” Michelin’s Crehan observes of the impact of the CARB and GHG rules on fleets. “But to be sure, a balanced approach is being taken by tire makers.”
He says it’s Michelin’s view that “no compromise in tire performance is required to meet the new rules” and that fleet owners should have “no inherent concerns around performance” about the tires they will be getting.
“That being said,” Crehan cautions, “it will still be important for fleets to work with their [dealers] to spec trucks—including their tires—correctly for the best performance in their given application. Plenty of fleets already approach fuel-efficient tires as de facto specs,” he advises. Yet others do not view them that way.
“Per CARB, fleets operating in California will need SmartWay-verified tires and others will need them if required by certain [green-conscious] customers and, of course, new trucks starting in 2014 will come with low-GHG tires,” notes Crehan.
“To be sure, the awareness of the effect tires have on fuel consumption is becoming more clear,” he adds. “Still, right now, there are many fleet managers who can ‘see’ their tread wear—but not the impact tires have on their fuel costs.”
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