Are super singles really that super?: Wide-base tires may not be ready for line-haul applications

Aug. 1, 2003

Imagine a solitary line-haul truck tire that provides lower rolling resistance and greater fuel savings than two conventional truck tires working together. It doesn't require special equipment to mount and demount, can be retreaded, and enables haulers to carry more weight and, in turn, boost their revenue.

That tire is the modern super single. And it stands to reason that all haul fleets would jump at the opportunity to capitalize on the product's inherent advantages. But that hasn't been the case. In fact, many tire manufacturers and dealers say the jury is still out on super singles for over-the-highway applications, and may be for quite some time.

Super benefits

Bridgestone/Firestone North American Tire LLC (BFNT) introduced its Greatec super single tire to the domestic market last month. Goodyear Tire & Rubber Co. plans to roll out two new domestic super singles by the fourth quarter of the year or the first quarter of 2004. Continental Tire North America Inc. (CTNA) will unveil two super singles in 2005 (see photo). And Michelin North America Inc.'s X-One super single has been available in the United States for more than two years. All four manufacturers agree that super singles offer tangible benefits, including:

1. Weight savings. "The biggest advantage is being able to lower the weight of the vehicle," says Guy Walenga, BFNT engineering manager for North American commercial products. "You can save 1,000 pounds going from steel rims and duals to (super singles) and all-aluminum wheels. Super singles typically are lighter than a standard dual set-up" -- in some cases, up to 70 pounds or more per wheel position.

2. Reduced rolling resistance, "due to the fact that less energy is wasted in deformation as the tire goes into and out of its footprint," says Walenga. With one tire instead of two, "you have fewer sidewalls that are deflecting."

"The whole idea is to reduce friction so there's less heat generated and the tires are allowed to roll" more freely for extra fuel savings, says Don Pelley, Michelin line-haul segment manager.

Super singles also provide "an increase in self-aligning torque, the vehicle's tendency to pull itself straight," says Cara Junkins, CTNA product planning manager. "Whenever duals are off in diameter, even just a little, the vehicle can pull to one direction or another." Super singles minimize that possibility, she says.

But can I get another?

This isn't the first time that manufacturers have pushed super singles as line-haul tires, according to Walenga. "In the mid-to-late 1980s, it became a big deal to try wide-base tires as a line-haul (option). Up until then, they were flotation construction tires."

But few fleets recognized the fuel savings benefits of super singles "because that wasn't a big issue at the time." Limited tread designs also proved to be a hindrance, and product unavailability was a major problem.

Lack of sales and service points remains an obstacle today. "In line haul, trucks can go anywhere," says Al Cohn, Goodyear manager of strategic initiatives. "A truck could be in Miami on Monday and San Francisco on Friday. If you're in Montana and run over a big nail, what do you do?"

Super singles don't offer the "limp home" capabilities of duals, according to Cohn. "If you get a flat, you have to pull over; you're stuck. If line-haul fleets are going to use super singles, you need a distribution network to handle the downtime."

Michelin has had time to establish a network. More than 500 locations throughout the U.S. stock the company's X-Ones, says Pelley, including independent dealers, truck stops and Michelin-owned Tire Centers LLC outlets. By the end of the year, the X-One also should be available in Mexico and Canada.

Currently, super singles hold more appeal for short-haul, regional haulers, according to manufacturers. "The people who have been purchasing and experimenting with them are the regional fleets, (whose) trucks are coming back every day or every couple of days," says Cohn. "I don't know of any pure line-haul fleets running any quantity of these tires."

Walenga says super singles have become more of a niche tire for tanker operations since weight savings are easily realized when hauling liquids.

Other issues impeding super single acceptance include:

1. Retreadability. Fleets usually average 1.8 retreads per casing in line-haul applications, according to Cohn. "You're only going to get one retread" out of a super single even under optimal conditions, he says. "These tires see a lot more stress and work than duals."

Manufacturers are working to address super single retreadability. Goodyear is in the process of preparing more than 170 locations throughout the country to retread super singles. MNA plans to offer super single retreading through its Michelin Retread Technologies Inc. facilities starting late this year or early 2004. The company currently retreads its X-One super single at its facility in Duncan, S.C., and sells the finished product through its dealer network. "We've secured casings via fleets who've run X-Ones for the last two years," says Pelley. "We have inventories of retreads."

2. Tread life. Super singles also tend to wear out faster than duals, according to Cohn. Initial tread depth for super single drive position tires fall into the 18- to 20/32-inch range, he says; the average drive tire's tread depth is in the 26- to 30/32-inch range. "There's less rubber to start with. Your final removal miles are lower." Super single vs. standard trailer position tread depths are relatively similar, he says.

3. Unit bulk and heaviness. A typical super single weighs 70% of two tires, but still weighs more than one normal truck tire. Super singles don't require special equipment or tools to mount and demount, "but you need to be Paul Bunyan to lift one of those things," says Cohn. He recommends using some sort of lifting device to minimize muscle strain. Super singles "may require different training" in terms of handling, says Walenga. Fortunately, they fit into existing inflation cages, "so that's not a problem."

Road reports

Most of Tom Martin's truck tire customers are construction firms. "We don't do a lot of long haul," says the commercial operations manager for Ted Wiens Tire & Auto Centers in Las Vegas, Nev., which sells 40 to 60 super singles a month.

A number of his clients have committed to super singles, even going so far as to buy new, super single-friendly wheels for their rigs. But some of his customers who had switched over to super singles have reverted to regular dual assemblies. "The single biggest reason is that when you get a flat, you're down," says Martin.

If the technology is ever going to succeed on a larger scale, "tire manufacturers will have to get their (commercial centers) and truck stops geared up for them," says Martin. "It's an expensive product to have on the shelf." He'd also like to see all super single manufacturers use metric dimensions "so brand A would be compatible with brand Z."

Maine Commercial Tire Inc., a four-outlet dealership based in Bangor, Maine, had a line-haul customer that used super singles on trailer positions. The tires ran adequately but were difficult to retread, according to Maine Commercial co-owner Jim Lynch. Most of the super singles the company sells are mounted on construction vehicles like dump trucks and cement mixers.

Bauer Built Inc. has started selling super singles "to a very limited number of line-haul operations," says Jim Fenn, executive vice president of tire sales and manufacturing for the Durand, Wis.-based dealership. "A number of fleets would try more of these tires if more field run-out data were available to better predict tread life and fuel economy. But there are still too many unanswered questions to accurately estimate actual cost-per-mile (benefits of super singles)."

"We've sold a few Michelin X-Ones to (liquid) haulers," says Don Aldridge, vice president of Roanoke, Va.-based White Tire Distributors. But no line-haul fleets have asked White Tire for super singles yet.

Aldridge says Michelin has stocked some of the dealership's locations with super singles "to make sure we have something on hand." But he believes widespread acceptance will not develop until other manufacturers establish their products in the marketplace. "CTNA's coming out with something, Goodyear's coming out with something, Bridgestone/Firestone's coming out with something -- but they're not proven yet."

Performance of existing super singles has been hard to measure. "I don't know of any fleets that have worn out the tires yet. That's how new (the technology) is."

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Switch-over costs may prove to be an obstacle to super single use. "I can't see your big freight carriers converting," says Aldridge. "If it turns out not to be viable, it may cost them a small fortune to (revert) back to duals. And then what do you do with the take-off stuff?

"In four or five years we'll have a better snapshot. But if I was a (line-haul) fleet owner, I wouldn't do it right now."

Super single manufacturers seem to accept the fact that not all end users will embrace the tires regardless of how hard they and dealers promote them. "If fleets want them, we're prepared to sell them," says Cohn.

"But there has to be a pay-off," says Walenga. The technology "is not that good yet that everyone should jump on the bandwagon. Fleets have to put a pencil to it."