Fleets use super single medium truck tires for different reasons. Some want to save weight. Others are interested in lowering rolling resistance. Where does retreadability fit into the picture? Is super single retreadability impeding or accelerating the technology's acceptance in the marketplace? It all depends on who you ask.
"You can't bring (out) a new radial truck tire without having designed into it the durability that's required for retreading," says Guy Walenga, Bridgestone Firestone North American Tire LLC (BFNT) engineering manager, North American commercial products. Load was the main concern when super singles were introduced for line-haul use some 20 years ago, he says. "Retreadability gradually became an issue as the tires saw more highway work."
When Michelin introduced its X One wide-base truck tire to North America in 2000, "it was very clear that the tire had to be retreadable," says Marc Laferriere, vice president of marketing for Michelin Americas Truck Tires, a division of Michelin North America Inc. (MNA). "Retreadability is a ticket to enter (the market). Fleets are conscious they need to retread to keep costs down."
The case for casings
BFNT parent company Bridgestone Corp. began heavily pushing its Bridgestone Greatec super single tire in the United States and Canada one year ago. The Greatec was originally used in Europe, where Bridgestone officials evaluated its retreadability, says Walenga.
"In the U.S., we sent (the tire) to Bandag and they developed a process and cap for it. We've taken worn-out tires back in, done inspections, had them retreaded, and put them back in the field." Some Greatecs have even been retreaded twice.
Bandag also has successfully retreaded several Continental Tire North America Inc. (CTNA) super singles on a test basis, says CTNA Director of Commercial Marketing Clif Armstrong. (CTNA plans to make its super singles available in mid-2006.) And Bandag has retreaded the Michelin X One.
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"We worked with BFNT and CTNA on evaluating their super singles to see if we could retread them using our process and equipment," says Clay Timmons, Bandag product manager, global dealer systems. "We confirmed that our process and equipment were suitable."
Timmons says there are challenges inherent in retreading super singles. "It's a bigger, heavier tire. And the buffing radius of these tires is significantly flatter than a medium truck tire.
"But they are essentially as easy to retread as a (normal) commercial truck tire."
Bandag's super single tread rubber compound "has been optimized for the bulk of the markets where super singles are being used, like liquid hauling and over-the-road applications," says Bob Otting, Bandag product manager, global tire products.
A super single's original quality and how well the tire is maintained ultimately determine ease of retreadability. "You want to make the tire as durable as possible to survive normal operating conditions so it can be retreaded," says BFNT's Walenga. "The casing is key."
The Michelin X One's casing package "is one of the best we've ever built," says Lafferiere -- thanks, in part, to the inclusion of the company's Infini-Coil belt that reduces detrimental casing growth at operating temperatures. "We'd be shooting ourselves in the foot if we used a throw-away casing."
Unfortunately, the condition of a casing deteriorates over time, says Al Cohn, Goodyear Tire & Rubber Co. marketing manager. User neglect plays a major role. "The tire's air pressure has to be right on spec," he says. Run a super single even 20% under-inflated "and there's no way you'll get a retread because the tire has been flexing. You'll have casing damage."
Super singles also store lots of heat because they're so large, according to Cohn. "When you under-inflate, you generate even more heat."
Goodyear plans to roll out its first super single tire, the G394 SST trailer tire, during the first half of the year. Its drive axle equivalent, the G392 SSD, is expected to come on-line during the second half.
"We've been running these tires for a long time in test fleets," says Cohn. Some of them have been retreaded. (Goodyear has more than 190 company-owned retread shops that can produce super single retreads.)
However, test fleets tend to treat tires more gingerly than over-the-highway haulers, says Cohn. "In the real world, tires get abused."
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X Ones (once more)
At least one-third of the "tens of thousands" of X Ones on the road have been retreaded, according to Laferriere -- not only in Michelin Retread Technologies Inc. (MRTI) plants, but in other retread shops as well. "We're being very diligent at inspecting the casings when they come back. Rejection rates have been no different with the X One than with any of our other tires."
For line-haul applications, MNA recommends that X Ones only be retreaded once. "Most of our line-haul customers are also retreading their duals once, and then they sell the casing."
However, MNA's two-month-old super single for garbage hauling and other urban applications, the X One XZU S, can be retreaded several times, according to Laferriere. "Most of the tires in these applications are going to be run 20,000 or 30,000 miles before being pulled off for retreading."
Seven out of MNA's 40-plus MRTI plants can retread X Ones. MNA plans to build new X One retread shops or retrofit existing facilities to handle X Ones "every month until we get all of them done," says Norm Ball, director of franchise business services for MRTI. "We may speed up (the process) if we think the market is growing faster."
MNA currently imports X One tread rubber from Europe, but plans to start making X One tread rubber in Georgia later this year. "The facility is being installed and we're doing some preliminary testing already," says Ball.
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Field reports
Don Aldridge, vice president of Roanoke, Va.-based White Tire Distributors, claims it's too early to tell if super single retreads will perform as well as conventional medium truck tire retreads. "I have a customer who's been running (super singles) for a year-and-a-half and is now thinking about retreading them."
However, the client isn't entirely convinced that retreading is his best option. "If the tread isn't placed on the tire perfectly, you're going to get vibrations -- more so than with just a standard dual," says Aldridge. If the super single is run under-inflated and its tread eventually peels, "it can cause major damage."
White Tire Distributors has another customer who is running super singles. "He just ordered 10 new trucks with (the tires), so I won't have any feedback from him for at least a year."
Great Bend, Kan.-based Becker Tire & Treading Inc. has been retreading super singles using Bandag's process for several years, says Becker Tire President Gary Albright. "We haven't had a problem at all." (Becker Tire also sells new Michelin and Bridgestone super singles.)
Super singles are a little different to handle due to their size and weight, according to Albright. The product's bulkier dimensions also forced Becker Tire to upgrade some of its retread machinery. "But Bandag worked with us and we got the system down. It was a small learning curve."
The nine-outlet dealership produces around 30 super singles a week -- mainly for two or three extremely large accounts. The process isn't much different than retreading conventional truck tires, he says. Profit margins between super single retreads and normal truck tire retreads are similar as well.
Otting says Bandag is still collecting information on how long super single retreads will last in the field. "Do our retreads wear as long as (regular truck tires)? Anecdotally, the answer is yes. But it's still early on in collecting the data.
"The other aspect is, 'Will a super single (retread) be retreadable over the lifespan of the product?' Again, it's too early too tell. We're in the first round of retreading these tires."
BFNT's Walenga cautions that retreadability is not a top concern for every fleet that uses super singles. "Some fleets only use new tires," he says. "They don't worry about retreadability. But I think the majority of users are looking at retreadability to reduce cost-per-mile. That makes (super singles) even more attractive."
