Flying Solo

For years, leading-edge fleet managers and vocational haulers have eyed the wide-based single tire as a replacement for their duals. To say the potential savings in weight and fuel economy are compelling would understate the issue, but past experiments with single tires have been disappointing, marked by a harsh ride, a tall profile, and jitters about what happens when one blows. Michelin, though, is out to change the paradigm on wide singles.

This time last year it introduced the X-One, a family of ultra-low-profile, wide-base tires designed to replace a set of duals-the XTA and XTE for trailers, and the XDA and XDA HT for drive axles.

Unlike the tall “super single” tires you see on construction trucks, Michelin’s X-One is sized at 445/50R22.5-an identical rolling radius to a low-profile 275/80R22.5 tire. This month, the company is expected to start producing 455/55R22.5 models-an 11R22.5 size that’s more in tune with the Canadian market.

Michelin’s lead has been followed this year with wide, flat-tread tire announcements from Bridgestone, Goodyear, and Continental. And with good reason: the potential benefits of these new singles are exactly what over-the-road trucking operations, distribution fleets, and specialty haulers have looked for from the “super-singles” but without the downside. With two sidewalls instead of four, there’s less energy generated in flexing, and so the tires use a minimum 4% less fuel. They weigh significantly less-more than 1000 pounds on a tandem tractor and tandem trailer when the wheels are taken into account. They ride better, generate less road noise, and, because they cover the pavement more evenly than a dual pair, they’re potentially more resistant to uneven wear, guaranteeing a long life. They cost about the same as a set of dual tires. And the switch of wheel and tire equipment require no modification of the vehicle, and makers are pricing the single tires competitively with a set of duals.

“The appeal is pretty broad,” explains Ralph Beaveridge, marketing manager for truck tires at Michelin North America’s Canadian office in Montreal. “Bulk fleets, they want the weight savings. The OTR guys want fuel economy.” In both cases, the investment in single tires can pay off quickly. “We had one customer, one running hard, with team drivers, change over the tractor, and the tires paid for themselves on fuel savings within two and half weeks.”

The promise of the market also has attracted Bridgestone, Goodyear, and now Continental. Of the three, Bridgestone is closest to production of its tire, called Greatec. It will be offered initially as a 435/45R22.5 rib and 495/45R22.5 block tread, but promised are 445/50R22.5 sizes-the same as Michelin’s X-One-in both a block and a rib. Greatec tires will mount on a 14-inch rim for the smaller sizes and a 17-inch rim for the 495 with special wheels made by Alcoa. Bridgestone also has a less restrictive distribution policy: for the next year, Michelin is supplying only Freightliner vehicles as original equipment (the X-One is available to anyone as a replacement tire).

Goodyear’s Marathon is a rib trailer tire, sized 435/50R22.5. Goodyear says a drive tire may follow.

These latter introductions were low-key in comparison to Michelin’s. Where its launch was heralded with major fanfare in association with Freightliner last year, Bridgestone merely staged its new tires, albeit in a specially constructed booth, at a small trade show this past spring. No press conference, no hoopla. Goodyear’s debut of the Marathon was even more low-key. You had to go find it at the company’s booth at the Mid-America Trucking Show in Louisville, Ky., the industry’s largest equipment expo. It wasn’t listed in the spec CD-ROM being handed out at the show. There was, though, a four-color information sheet if you knew enough to ask for it.

The different launch styles probably reflect each manufacturer’s point in the development of the new wide, flat-tread tires. Michelin has been developing the product for three years, starting first by evaluating tires from Europe, then producing early prototypes at its Greenville, S.C., plant. Bridgestone is currently importing tires but is understood to be on the point of producing them in the United States.

Goodyear is only a short way into the development of the trailer tire with a wide drive tire coming along later. Continental Tire is expected to release a wide tire as well.

The tread profile is the most noticeable feature of these new-generation tires. But there’s more to them than that.

The inspiration comes from the bus industry in Europe. The early Michelin and Bridgestone tires, with the 495/45R sizing, were designed for inter-city, high-mileage buses, where their fuel economy and ride pay off big-time, and they can be set further apart on offset wheels to maximize floor space inside the bus.

On trucks, the priorities are different. The size of the tire is dictated by state and provincial mandates on minimum tread width/loading to avoid rutting the highways. The rules differ from jurisdiction to jurisdiction, but the toughest in the United States is 500 pounds per inch. That dictates a tread 17 inches across to carry 8500 pounds or 17,000 pounds per axle, 34,000 pounds for a tandem. The other defining dimension is the overall diameter of the tire, initially chosen to be the same as the low-profile 22.5-inch tire. The result is a tire that has a 445 tread width and a 50% aspect ratio-the ratio of height from the rim to the tread versus the tread width. The Michelin tires are rated at a 10,200-pound carrying capacity.

In Canada, Ontario does not have specific restrictions for tire loads, so you can run unencumbered there. Quebec allows axle loads up to 9000 kg on a set of duals, but only 8000 kg for a single tire. That’s fine if you’re running 80,000-pound GCWs into the United States, but too great a penalty if you’re operating elsewhere. Outside Quebec and Ontario, loads for axles with single tires fall under the Memorandum of Understanding on vehicle weights and dimensions. The limit is 3000 kg per tire for a single tire, meaning wide tires like the X-One and Greatec wouldn’t be feasible.

“The big concern for people in government is the effect a loaded-up single tire will have on pavement,” Beaveridge says. “Our challenge is to prove that this particular single tire design, with its width, does not create any more strain on the road surface than does a set of duals-that it’s ‘damage neutral.’ We’ve established that through testing, and we’re hoping that the provinces in Western and Atlantic Canada will make the appropriate changes to recognize these tires. Clearly, they’re not what anyone had in mind years ago when they wrote the rules on singles.”

There are many reasons the tires are the same as the standard 22.5. For one, they replace existing wheels and tires on most trucks with no changes to gearing or the vehicle height. They run at the same pressures, too.

Perhaps more critically, if no replacement tire is available for a blown single, a driver always has the option of removing the wheel and installing a dual pair as a get-the-load-there measure.

Michelin is going to great lengths to have not only service tires available in the market, but retreads as well. But the company acknowledges that replacements in the initial stages of marketing the tires can be a problem.

It’s certainly something Bridgestone and Goodyear believe. Both see the market for these tires as more regional than over-the-road, and identify bulk haulers, fuel distributors, and other weight-critical applications as targets. Saving 1000 pounds or more is a big deal here, and the regional nature of the operation means never being far from the tire distributor or maintenance shop.

The weight savings are obvious with the single tires on the two-inch offset Alcoa wheels. The 22-by-14-inch rim aluminum wheels have been introduced to support the introduction of ultra-low tires from all three manufacturers, though Michelin says there has been interest in using the wide tire on a similarly sized steel rim, albeit at a trade-off of some of the weight advantage.

In terms of packaging, the overall height of the tires gives some additional stability to high CG loads like tank and bulk trucks running “super-singles” today. The X-One centreline of the tire, for instance, sits two inches outboard of the dual pair each side. This offers a four-inch increase in effective track and a 13-inch greater width between the inner sidewalls. The additional inside clearance would permit a wider, lower tank, for instance. However,

Michelin says the first real optimization may come in response to a livestock hauler who could use additional trailer width for space for larger animals.

But Michelin’s 57-million-mile development of the X-One included some notable OTR fleets-names like Schneider, C.R. England, and Simon, all very much highway fleets where the 4%+ fuel savings are key. The fuel economy savings were documented for the Michelin X-One during the testing phase and are presented in an SAE paper co-authored by Freightliner engineers Mark Markstaller and Al Pearson and the X-One designer Ibrahim Janajreh. Against other fuel-efficient tires, the X-One consistently showed a 4% or better advantage. Over other less fuel-efficient tires, the savings could be as much as 10%.

Tread wear is comparable or even a little improved over standard Michelin low-pro tires, says Janajreh. And the lack of irregular wear counts in the big tires’ favor, too, especially in trailer positions.

The tires get the same wear rate as duals in a similar application, and eliminate problems with mismatch duals or mismatched air pressures.

Wear was a concern expressed by Goodyear’s Al Cohn, though he was using Goodyear’s trailer tire with its 15/32nd tread depth as an example. If it were used in a drive position, it would need replacing earlier than a conventional drive tire with the more usual 24/32nd of the wide XDA X-One or the extra deep 28/32nd of a high-mileage block drive tire, he said.

For Michelin to gain a foothold for the X-One among over-the-road fleets, it has to get drivers on board. However good the fuel economy and payload potential of the tires, they will do no good if drivers walk. And, according to Michelin, driver reaction has been positive once preconceived notions are dispelled.

In contrast to earlier experiences with wide tires, drivers in test fleets have said the X-Ones outperform a dual pair on overall ride and traction, even in winter. That’s not something that was anticipated, but the tires seem to be able to put more rubber on the road more of the time, especially in packed snow.

Initially, the biggest concern among drivers-one Michelin, Bridgestone, Goodyear, and other makers are working hard to address-is their ability to control the vehicle when a tire blows out. At Michelin, a demonstration using a tire with a special blow-off valve in the rim showed the truck behaving normally when the tire suddenly lost pressure, stopping easily and controllably even when both drive tires on the same side deflated at the same time.

Incredibly, the rims never touched the road. And although the tires had been driven totally deflated as the truck was brought to a stop, they were remounted to the rims and used several times more.

Noted during the testing and also promoted by Bridgestone in its marketing is that the wide tires are quieter running than conventional dual pairs. Michelin also reported that in testing, the X-One exhibited consistent handling in cornering on the special skid pad.

Instrumentation backed up the subjective driver evaluations of noise and ride enhancement. Not surprisingly, during the on-highway fleet testing, the drivers of the evaluation trucks were frequently questioned by other truckers on the characteristics of the tires and were quick to defend them against negative comments. Michelin’s marketing vice-president Randy Clark says that part of the appeal to drivers was being seen as pioneers in this new technology.

There’s no doubting Michelin is hoping for great things from the X-One, though even Beaveridge concedes that, like competitors Bridgestone and Goodyear, Michelin’s early efforts will be concentrated towards the obvious markets where weight is a primary concern.

And once tire makers convince provincial governments that these new tires are no more harmful to pavement than what’s already on the road, fleets will be able to realize their ability to cut fuel and other operational costs, with almost no downside this time around.The traditional way of looking at tire costs is product-only: new tires, retreads, and wheels. But product is only half the pie. The other half involves service costs: administration, warranties, carrying inventory, and so on. If you’re not managing this stuff, too, you’re no doubt missing opportunities to save big.

Part of the problem with managing tires is that they’re hard to track. Bar codes and other visible markings are scrubbed off in no time.

The answer is to leave your mark inside the tire, says Ghislain Lemire, vice-president of Syscan International. The Montreal-based developer of tire management software worked with a German microchip maker to produce a small but rugged transponder you can patch onto the casing of the tire. The chip, which costs less than $5, has a unique code you can read with an RFID (radio frequency identification) scanner after the tire has been mounted on the vehicle.

“Having the chip to identify the tire is very important to us because it enhances what you can do with our management software,” says Lemire. “Once you know which tire is which, you can import that data into the software and track how the tire is being used, how it is performing, and what costs are associated with it. You can build better preventive maintenance schedules, analyze the performance of different tire specifications, verify warranty information, and control inventory throughout the life of the tire. The end result is you make better decisions about which tires are best for you.”

Syscan’s transponder does not provide temperature or pressure readings-at this stage in development, such chips need a battery, and they won’t survive the retread process. And it is not yet compatible with RFID scanners other than a Psion device Syscan offers.

However, the Syscan chip is simple enough to install yourself, and the company is working to make other handheld scanners compatible.