Single-Minded

If you ask owner-operator Tom Menzel of Mequon, Wis., why he uses super singles, he’ll tick off all the reasons niche haulers like him typically spec the big drive tires, starting with lighter weight and better weight distribution.

Menzel, whose 2002 Freightliner Argosy has a heavy frame and a 50-meter crane, says those aren’t the only reasons why over-the-road truckers should consider replacing their duals with the new line of low-profile super singles.

“Even if I was not doing heavy hauling and off-road stuff, I would still be a super single user,” Menzel says. “The improved handling and ride would motivate me to continue using them.”

Wide profile drive tires are making inroads in over-the-road applications after years of being relegated to niche and off-road hauls. Manufacturers say the tires are easier to maintain, allow for more payload, are cheaper to operate and more fuel-efficient than duals. Some drivers are getting more traction and a smoother, safer ride.

Perhaps the best feature of the new crop of super singles is their size. While super singles have existed for decades, they typically had a larger rim diameter than standard dual tires. Trucks spec’ed for older super singles required costly retrofits to accept standard duals. But the new wide tires have the same wheel diameter, 221/2 inches, as duals and can easily be added to a typical truck without costly changes to its setup. The only additional investment in equipment is wider rims.

Michelin is the only tire company currently offering super singles in a 221/2 -inch size configuration, but Bridgestone and Continental have designs for low-profile tires in testing and expect to be on the market in the next two years. Goodyear is also testing as it decides whether to introduce the tires.

Toyo, too, is considering a low-profile single. Dan Gilbert, Toyo’s director of sales for commercial products, says he doesn’t know if the tires, successful in Asia and Europe, will make it in the U.S. market.

“There are a lot of pros and cons – by replacing two tires with one and reducing weight, the overall cost should be less,” he says. “But the big downside of a super single is what happens when you have a tire failure. You’re dead on the road.”

That’s a common concern of truckers because a blown dual puts greater weight on the remaining inflated tire. “They worry that they’re not going to be able to limp to the next exit,” says Don Pelley, line haul segment manager for Michelin in North America. “If you’re loaded, and a dual goes down, you should stop anyway. But most guys go on to a service center.”

Drivers also fear that they will lose control when a super single blows out because there’s no remaining dual to shoulder the load. “That’s not the case,” says Guy Walenga, Bridgestone’s engineering manager for commercial truck tires. Bridgestone has done blow-out testing on its existing super singles, which have a higher center of gravity than lower profile super singles. In each instance the tires performed as safely as duals. Because the new tires have centers of gravity lower than existing super singles, Walenga expects them to do better.

Michelin’s X-One hit the market two years ago and is currently the only available low-profile model. Other manufacturers are testing designs with plans to introduce.

Truckers also worry about having so much money invested in one tire. The low-profile super singles cost roughly the same as a set of duals. But replacing a damaged single costs much more than replacing half a dual set, says Cara Junkins, manager of commercial planning for Continental. But these cons, cited by skeptical truckers, don’t outweigh the pros, say tire makers.

“By going with one tire rather than two, fleets have lower inventory costs,” she says. “Trucks get better fuel economy because only two sidewalls are flexing. There’s less rolling resistance.”

Tire manufacturers say super singles average 3 percent better fuel economy than duals, largely due to aerodynamics and materials. Super singles are more aerodynamic because only four sidewalls per axle, instead of eight, are exposed to airflow.

The tires also feature advanced rubber composites, technology that will eventually make it into duals. Much of that technology is designed to overcome the structural limitations of the extra width, says Goodyear’s Al Cohn. “You’ll need more support,” he says. “The tires have a heavier-duty construction than duals.”

From all reports, the tires seem to handle better and offer better stability, Cohn says. That’s what owner-operator A.J. Leonhard, of Byron, Ill. saw when he put a set of low-profile super singles on his 2000 Peterbilt 379. Leonhard says he didn’t buy the tires to save weight, but for style and comfort. “I’ve had them for two weeks,” he says. “I love the ride. The truck has immense traction. They handle well.”

The wide tires can straddle many potholes and ruts, making a smoother ride, Leonhard says. He’s considering putting them on his dropdeck trailer, even though he seldom hauls loads that push his gross vehicle weight near 80,000 pounds. Leonhard also says the tires expose more of the drum brake to the air and cool brakes faster, offering an unexpected safety benefit.

There are other safety factors. Using singles, there are fewer tires and no hard-to-reach inner tires. Most uneven tire wear occurs because one dual has less air in it than another. That problem is eliminated with singles, Junkins says. “Maintenance ought to be easier,” she says.

The tires are also safer, Junkins says, because when two duals have different inflation, the load shifts to the tire with more inflation. That puts greater pressure on it, often without the driver’s knowledge, and can lead to a blowout.

Super singles also have a smaller footprint than a set of duals, which means less friction and less rolling resistance, and by some reports, better traction. Bridgestone’s Walenga says older model super singles generally had the same traction as the duals, but that’s changing. “The tires have a footprint 87 percent of the size of duals,” he says. “We hear that in snow these new singles perform well.”

Weight savings can be considerable, too. A set of super singles on aluminum rims can cut nearly 500 pounds from a tractor equipped with steel rims and duals. The tires can also be fitted to trailers, so a retrofitted tractor-trailer combination can lose half a ton.

Continental is currently testing its low profile super single.

Weight is a big reason why Tom Menzel has spec’ed super singles since 1985. Since his new truck has a double frame to support a 50-meter crane and a steer axle that’s rated at 20,000 pounds, he values any weight savings he can get. Tankers have embraced super singles for years for weight reasons.

For some owner-operators, the added capacity will mean more business, says Michelin’s Pelley. “Their equipment might be too heavy for some loads, and they’re passed over,” he says. One driver who outfitted his rig with Michelin X-Ones told Pelley that instead of hauling larger payloads, he could now afford to install a generator on his truck.

Another benefit of super singles, Junkins says, is lower federal excise tax. Because the tax is applied per wheel, the cost is less.

While older model super singles did not wear as well as a set of duals, the new tires should be more competitive. Still, they have less overall tread depth and may not get the same number of miles, Bridgestone’s Walenga says. However, retreads for super singles should be cheaper than duals, and savings from fuel and load capacity should also compensate for fewer miles

For truckers who choose to outfit their tractors and trailers with the tires, another problem crops up: Old steer tires can no longer be rotated to the trailer. Pelley suggests selling those casings instead.

Availability is another concern, but Walenga says that’s being remedied. “There are so many points of sale today, and truck stops are able to handle the issue. These tires will be out there and relatively easy to find.”

Availability has not been a problem for long-time user Menzel. “In 17 years, I don’t think I’ve ever been on the side of the road for want of a tire for more than an hour,” he says. “You can be there that long with a common set of low-pro 225s. There have been times I’ve had to take a brand of tire that I wouldn’t ordinarily buy.”

Before Menzel ordered his new truck, he checked truck stops for low-profile super singles. “Any of them I stopped at had a super single on the rack,” he says. Even a stop in Fond du Lac, Wisc., had two super singles that fit. “That was never the case in the past.”

Despite all the benefits promised by super singles, the tires have a long way to go to convert truck drivers who were raised on a diet of duals and myths about wide tires, but the manufacturers believe that will change. “Those owner-operators who are very conscious of operating costs,” Pelley says, “will want to use the tires when they look at the bottom line and see they can add savings for extra fuel and add the extra payload.”


SUPER SINGLE PROS

  • Up to 5 percent more fuel-efficient.
  • Can save up to 1,000 pounds on tractor-trailer.
  • Easier to maintain – four tires instead of eight.
  • Better handling and ride.
  • Lower inventory costs for fleets.
  • SUPER SINGLE CONS

  • Truck cannot limp to next truck stop to replace a blowout.
  • Expensive to replace if damaged.
  • Heavy tire is hard for a single person to change.
  • Availability of replacements.
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