By Paul Abelson
senior technical editor
Five years ago, Michelin surprised the trucking world by introducing X-One wide-base single tires, direct replacements for dual low-profile 22.5 wheels and tires.
Unlike Goodyear’s 425/65R22.5 Super Singles, which are high-capacity oversized tires with conventional aspect ratios, the X-One came out as a 445/50R22.5, requiring a 14-inch wide wheel.
- Lower tire and rim weight/increased payload;
- Ease of maintenance - no inside dual tire pressure to match or maintain;
- Elimination of mismatched dual height and/or pressure, which could provide more uniform wear;
- Reduced tire and rim inventory;
- Improved fuel economy;
- Potential to lower rig’s center of gravity for improved handling and stability.
- Tires/wheels not standardized in fleet;
- Increased treadwear rate;
- Possible reduction in wet traction;
- Limited availability on road;
- Reduced vehicle resale value.
- Possible legal restrictions of nonsteer axle application of wide-base singles should be thoroughly investigated before finalizing size selection.
- From the 2004-2005 Recommended Engineering Practices Manual.
Subsequently, Bridgestone brought out its wide single, the Greatec. With either Michelin’s X-One or Bridgestone’s Greatec, the rolling radius of a properly mounted tire is the same as for the 22.5 duals it replaces. In an emergency, duals can be mounted on one axle end, with a wide single on the other.
Are these new tires for you? Land Line asked each of the three major tire makers - Bridgestone, Goodyear and Michelin. We also checked with some OOIDA members on the Maintenance Forum on the association’s Web site.
Bridgestone is selective about its wide-base applications.
Guy Walenga, their commercial tire engineering manager, said they’re excellent in an application where weight savings can readily convert to increased revenue through greater payload, but fuel economy can be improved about as well using fuel-efficient M720 drive and R195 trailer tires. The duals offer more miles to removal.
Although there are some improvements in ride and stability, Walenga primarily recommends Greatec for weight-sensitive loads. They’re not for spread axles because of excessive scrub.
Michelin has taken a more aggressive approach, according to Michael Burroughs, product manager. The advantages in ride, handling and at least 4 percent fuel economy are as important as the weight reduction. By going from four sidewalls per axle end to two, there is a 15 percent improvement in spring rate.
“That’s equal to going from a spring to an air suspension,” he said, adding that there’s improved geometry, too.
“Even though each tire’s outer edge is slightly inboard of duals, overall track increases by three inches. That improves torsional stability and raises the rollover threshold by about 3 mph, a significant safety improvement.”
Michelin officials think most operators can benefit using X-Ones. They have a satisfaction guarantee. If a buyer is not satisfied with the X-One’s ride and handling within the first 60 days, Michelin will buy them back at the full purchase price for the tires and 75 percent for the wheels, plus a $30 per wheel end service allowance. They also offer a conversion incentive of $400 per vehicle, tractor or trailer, for up to 10 vehicles.
Michelin added 455/55R22.5 sizes for waste and urban trade applications. At 130 psi, each axle can support 23,400 pounds, about 3,000 more than the 445/50R22.5 at the same pressure. The smaller size can support 17,640 pounds per axle at 100 psi.
Goodyear has taken a wait-and-see attitude, according to Al Cohn, marketing manager. He sees a niche market where “the pluses don’t often outweigh the minuses. We’re staying on top of it, testing our own tires, but we’re not ready to introduce (any) at this time.
“Each fleet has to determine its own circumstances. A 300,000-mile life may drop to 200,000. Two retreadings may drop to one or none. And fleets need to monitor air pressure very closely. I don’t know of any owner-operators using wide singles. If they do, the successes probably involve bulk hauling,” Cohn said.
Based on comments posted in the OOIDA members Maintenance Forum, owner-operators have mixed feelings about wide-base tires.
One member indicated success with the X-Ones that came on his new truck. That overcomes one major concern, the cost of switching from duals and buying wheels with tires.
Concerns expressed on the forum related to the inability to limp home with a damaged tire, problems carrying a spare, difficulty handling the extra-heavy tire and wheel assembly, and the lack of field service. Michelin addressed the last item with service providers including 1,100 dealers and 160 truck stops including Petro, Pilot, Flying J and Bosselman locations.
Paul Abelson may be reached at firstname.lastname@example.org.