TIRES: From the lab to the road

Beyond being oohed and aahed by tread design, there isn't much to get excited about a new tire ready for the road from just looking at it. But step into the labs where tires are literally cooked up with highly proprietary recipes of rubber, steel and sundry chemicals, and it is crystal clear every tire is much more than round and black. That's especially the case with truck tires, which must be engineered

Beyond being oohed and aahed by tread design, there isn't much to get excited about a new tire ready for the road from just looking at it.

But step into the labs where tires are literally cooked up with highly proprietary recipes of rubber, steel and sundry chemicals, and it is crystal clear every tire is much more than round and black.

That's especially the case with truck tires, which must be engineered and manufactured to meet any number of criteria — fuel efficiency, long mileage and retreadability, to name just the top three — and in varying degrees based on customer preferences.

No wonder truck tire engineers have carbon black in their veins. Their work in the lab never ends and it is driven by what is happening on the road, to their fleet customers whose needs shift with the ever-changing dynamics of the trucking industry.

Right now — and for the foreseeable future — saving fuel trumps all other considerations for many fleets, and tire makers are rolling out products with that clearly in mind; however, they are not doing so at the expense of fleets whose main concern may remain original tread life or even tread wear, especially as it affects retreadability.


“There's no doubt that in the last six to eight months, fuel has moved from a top five concern to being number one on everyone's list,” says Guy Walenga, director of engineering-commercial products & technology for Bridgestone Bandag Tire Solutions (BBTS). “Our current product line has technology that addresses fuel economy, which we began addressing long before the cost per gallon took off.”

According to Walenga, tire technology that enhances fuel economy centers on the tread compound as well as casing design, including the sidewalls, and the tread — the biggest single piece and the renewable piece via retreading,

“Every developmental tire program looks at miles per gallon and miles per 32nd,” he adds, “but, yes, decreasing rolling resistance is now at the top of the list. Most fleets are sophisticated enough to know what suppliers offer both in terms of what they can spec on their next [vehicle] purchase and replacement tires.

“In our case,” he continues, “our premium linehaul steer and trailer tires are our most fuel-efficient offerings; they were designed from the get-go to provide the lowest rolling resistance. As for premium drives, we offer the M720 with 26/32nds as the most fuel-efficient choice and the M726EL with 32/32nds as the high-miler.”

Walenga maintains there is “continuous evolution of truck tires via improved compounds but also more durable casing designs. New sidewall compounds will both reduce rolling resistance and help protect against [deterioration due to] aging.” He adds that changes in bead design will also help improve durability and cut weight and may even help reduce rolling resistance.

He points out that retreading is another avenue to boosting fuel economy. “Bandag has introduced FuelTech retreads for drive and trailer positions that improve rolling resistance compared to more mileage-oriented treads. It is safe to say that fuel-efficient retread designs are more fuel-efficient than they have ever been.”

“Most popular right now is our FuelTech drive and trailer retreads,” confirms Chris Hoffman, manager of global tire products for Bandag, part of BBTS. “These are the most fuel-efficient retreads we offer, and the growth in demand has skyrocketed thanks to $4-and-up diesel fuel.”

Hoffman points out that fleets that were running high-mileage tires but want to up their fuel efficiency can do so quickly by switching to a more fuel-efficient retread design. “We've seen fleets gain as much as a 10% jump in fuel efficiency by switching treads,” he states. “We feel that Bandag's are 1 to 3.3% more fuel-efficient than other retread brands.”

According to Hoffman, that performance is “due to proprietary tread compounds that ensure very low-rolling resistance plus the tread designs themselves. We started launching these [fuel-efficient] products back in 2002, so you could argue we were ahead of the times.”


“Keep in mind where rolling resistance comes from,” points out Don Baldwin, product marketing manager for Michelin Americas Truck Tires. “A good portion of it — 40% — comes from the tread area. You have to consider the tread design; solid rib is better than lug for fuel economy because the movement of the lugs is greater. Then there's tread depth; shallower is better for fuel economy because the deeper the tread, the more energy is expended to move the tire. And there's the rubber compound itself. What you want is one delivering lower hysteresis, that is, it does not build up heat, and good wear characteristics.

“The sidewall,” he continues, “contributes 30 to 40% as sidewall flexing creates energy, which becomes heat. The sidewall construction and the materials used contribute to this. If you construct the sidewall with stronger but lighter steel and thinner rubber, that will offer the best solution along with maintaining the proper pressure.”

Baldwin says the bead area is also important. “You want the tire to sit fixed to the rim properly to avoid unnecessary movement. The bead design must fit well with the wheel but still allow easy mounting. The material used is also key so the bead does not slip on the wheel.”

Curtis Decker, senior engineer-product development for Continental Tire North America, says technological advances are allowing truck tires to deliver both “world-class fuel-efficiency and longer original wear.” He says a case in point is “Continental's premium HSL line, which is as fuel-efficient as anyone else's, but provides a tread 2/32nds deeper on the drives. All the major tire suppliers are at the high end of technology,” Decker observes, “and we have focused on maintaining higher mileage on drives than most other fuel-efficient tires available.

“We've had to examine how much fuel efficiency you can derive from a casing and still allow for excellent retreadability.” Depending on the retreader a fleet uses, Decker points out, “the fleet may or may not keep their own casings so our approach is to provide a durable casing that can compete with any out there [in terms of retreadability].”


Decker says compounding can be customized based on what performance objectives are determined for each tire. “Every manufacturer's compounding is essentially a proprietary blend of the same basic components. These components, such as carbon black, are purchased on the open market where they are offered in different grades with different attributes, which helps make tires unique by brand and type.

“When it comes to compounding, it's important to understand even a small tweak in the formulation can make a huge difference,” he continues, “and that helps each manufacturer attain individual ‘signatures’ for their tires.”

Decker says what happens on the factory floor also impacts tire performance. “In every manufacturing process, we must protect the rubber compounds and the other tire components,” he explains. “It's not just a matter of how much rubber you can pour.”

Allowing that some fleets may want the best of both worlds, mainly fuel efficiency and long wear, Continental just announced a new steer tire — the HSL2 (Heavy Steer Long Haul) — as the first in a series of what it calls “next generation” fuel-efficient tires.

The HSL2 uses an innovative tread compound to deliver a “significant” increase in removal miles yet also increase fuel economy. The tires also feature Continental's patented FlexLock technology, an interlocking mechanism that promotes even tread wear across the footprint and increases stability. What's more, additional vertical sipes paired with FlexLock help prevent excessive heat buildup in the tire's shoulder.


Decker points out that for fleets, “cost-justifying fuel efficiency is very complicated. A lot of fleets say they may be getting more fuel efficiency from a given tire, but they know they can see the original mileage and can measure that savings easily. Having long-wearing tires can allow them to sell off a truck with the original tires still on it.”

Tim Miller, Goodyear marketing communications manager, says the most fuel-efficient tire offerings are typically aimed at long-haul use given that “in start/stop applications, tires play a smaller role in fuel economy.”

That remains as true as ever, but he says what has changed over the past 25 years or so of tire developments is that gaining fuel economy no longer means having to give up tread life. “The miles per 32nd provided by our Fuel Max linehaul tires are very similar [to baseline tires]. You do give up a little original mileage on drives — 26/32nds on a Fuel Max LHD vs. 30/32nds for a G372. You give up a little original wear, but the miles per 32nd are about the same [over the life of the tire].”

Miller says Goodyear's Fuel Max tires use a tread design and a dual-compound construction that helps reduce the amount of energy generated within the tread for low rolling resistance as well as an all-steel, four-belt package that reduces pressure on the tread while adding strength for low-rolling resistance and long tire life.

Miller says getting the most out of tires means keeping retreading in mind, too. “Tire makers have jumped into the retread market in a big way in recent years because it makes sense to offer retreads that are complementary to original tires to help keep customers buying from us. Not for steers, but for our drive and trailer tires we make every effort to have a complementary retread available.”

While the tire's contribution to fuel efficiency and its wear rate remain the top two concerns of on-the-road fleets, Miller says some of those truckers pushed Goodyear to make wider use of its DuraSeal built-in sealant technology, which essentially is a compounding technology.

If a DuraSeal tire is punctured by a nail, a yellow, gel-like rubber compound built into the crown of the tire surrounds the nail and seals the tread puncture. Miller says DuraSeal can seal up to a quarter-inch tread puncture, and it can do so repeatedly without the tire needing to be repaired or the sealant reapplied.


DuraSeal was initially offered on tires targeted at such mixed-service workhorses as refuse haulers and cement trucks. “But long-haul customers asked us to bring DuraSeal to trailer tires because they incur lots of punctures just backing into docks,” relates Miller. “We turned that request around in just a few months and now our Unisteel G316 LHT is available with DuraSeal as well as Fuel Max technology.

“They are different products,” he adds, “because having DuraSeal in place does increase rolling resistance a bit at this point. But the DuraSeal trailer tire is gaining momentum out there because it can greatly reduce downtime.”

According to Rick Brennan, vp-marketing for Kumho, the South Korea-based tire maker is “really now jumping into [North America] with expanded production capability, thanks to a new factory opened in China.”

At the same time, Brennan says Kumho is zeroing in on improving the rolling resistance of its tires with special attention being paid to new belt materials and designs that will cut weight and thereby help reduce rolling resistance.

“We are also using new production methods to make tires more uniform so they roll ‘truer’ to help reduce irregular wear,” he continues. “Kumho is offering deeper 30/32nds tread on drive tires to lengthen original tread wear, and we feel original casing life is important too, as that reduces the number of tires that get disposed of instead of retreaded. Certainly, tires will become more environmentally friendly in the next few years, both from the point of view of disposal and air quality.”

By way of introduction to a truck tire brand that is gaining presence here, Aaron Murphy, vp of CMA, the subsidiary for Double Coin tires in North America, says the brand was established in China in the 1920s and is now the 19th largest tire manufacturer in the world.

“Our product line for North America is extensive, covering everything from all-position tires to application-specific tires for on/off-road trucks and specialty trailers,” Murphy points out. “Our view of technology is it helps us meet the goal of delivering high-quality tires at a reasonable cost. While acquisition price can be important, [in this market] delivering value in terms of performance outweighs that in our minds.”

Murphy says the rapid run-up in the price of diesel this year has led Double Coin to focus more heavily on developing more application-specific tires with, of course, a greater emphasis on reducing rolling resistance.

“The endurance and strength of our tires have been well regarded,” he says, “but there is no doubt today's fleet owners are looking at fuel costs like never before.” Murphy says this concern is being addressed on several fronts — “from tread compounding, to the weight of the tire itself, to internal component changes, including bead structures, much is being done to both reduce rolling resistance and tire weight to enhance fuel savings for steer, drive and trailer tires.”

Murphy adds that in recent years, Double Coin has made “great strides in bringing our truck tires to market here and our goal is to grow our share by being the best value tire provider, period.”


“Business is up right now and we're seeing many fleets coming back to retreading,” advises Marge Connors, marketing & communications manager for Marangoni Tread North America (MTNA), a subsidiary of the Italy-based firm that is the largest independent retreader serving the U.S. trucking industry.

Connors says MTNA's technology for retreading is distinctive. “Ringtread is patented and is one contoured piece of precure tread that delivers excellent mileage, reliability and wear characteristics compared to a conventional ‘flat’ precure process,” she explains.

“The contour of the Ringtread is designed to match the natural curvature of a casing to maintain balance and allow for cool running and even wear,” Connors continues. “The elimination of a tread splice in the precure treads eliminates a weak spot, a heavy spot, the likely place for contamination that can lead to [retread] failure.”

What's more, she explains that because the Ringtread is designed round, not flat, and without any splicing, it “fits the casing as it should.” Connors says Ringtread was ahead of its time in its introduction of contour-shape tread technology. Altogether, according to Connors, the unique Ringtread approach “produces 20% more miles and 1 to 3% better fuel economy than conventional retreads.”

Connors says that MTNA also expects to bring technology to bear on production costs, which are being driven up by the rising prices for raw materials. “We're putting a lot of emphasis on improving our manufacturing efficiency but also on supporting our independent dealers through our technical staffers, who can address both the process and the technology behind it.”

New math

When is one bigger than two? According to some tire makers, it's when one wide-base “single” tire replaces a set of duals and delivers better fuel economy.

Wide-base truck tires are not new, but their positioning as a fuel-saver has been strengthened in recent years, especially by Michelin, which has been aggressively marketing its line of X One tires in North America.

To be sure, other tire suppliers are in on the wide action and still others are expected to roll out their wide entries by next year.

Ask Don Baldwin, Michelin product marketing manager, why rolling wide is the way to go and the answer is as simple as subtraction. “Things have been done to improve the rolling resistance and wear performance of duals, but going to wide-base tires is a quantum leap because you are getting rid of two sets of sidewalls,” he states. “Sidewall flexing creates heat, which impacts rolling resistance and wear. The X One is 4% more fuel-efficient than our best dual, and the savings can range up to 10% depending on the tire.”

Baldwin also points out how wide tires address the conundrum tire engineers face with tread depth. “Less tread depth produces less rolling resistance, but then there is less material to wear. That can be addressed by compounding, but by going wider, we can also maintain more volume for wear but at a lower tread depth. So, wider tires are both good for wear and for maintaining a good level of rolling resistance.”

Baldwin sees two other advantages to single tires. “Running with X Ones will cut weight by 800 to 1,000 lbs. per truck, allowing for added payload. On top of that, these tires do away with the whole issue of maintaining the inside duals. It's not a bad thing either to get service on the road for a wide tire rather than making gators of new or retread tires that come apart from low pressure.” He closes his pitch by relating that by Michelin's estimate, there are now over 900 service points of various types available for wide tires — and there are over 60,000 trucks now rolling on them here.

Guy Walenga, Bridgestone engineering director, says that while the company markets Greatec drive and trailer single tires here, a “wide-base tire is not necessarily the most fuel-efficient. Then there is the question of retrofitting tires and wheels [when switching to them]. We feel there is an advantage to stay with duals if what you are seeking is just fuel economy and that wide-base tires are best suited for a weight-sensitive application in which the weight saved can be translated into greater payload.”

Continental, says senior engineer Curtis Decker, “plans to roll out wide-base linehaul drive and trailer tires in the first quarter of '09 as we want to be competitive in that segment. My view is there are some applications, like liquid bulk hauling, that are a natural for the tires due to the weight savings they provide.”

Kumho marketing vp Rick Brennan says the company is “working on a wide-base tire aimed at linehaul trailers and tractor drive axles. It's something of a hot button here. We're waiting for production capacity [to free up] to allow introducing a wide-base Kumho,” he adds, “and that is probably eight months out from now.”

Goodyear communications manager Tim Miller says the company currently markets wide-base tires in Europe and has imported some for customers here to try out. “Our philosophy is we want to make tires fleets can switch to easily via a conventional [dual] solution. The market here may [eventually] demand singles in a big way, but we are not seeing that yet. We make them in Europe, however, so it would not be difficult to turn that spigot on.”

Double Coin vp Aaron Murphy says their take on wide-base tires is that clearly “everyone is looking at them as a viable option toward saving fuel. We are studying this application but are not focused on it as we prefer right now to emphasize enhancing the performance of our existing tire line.”

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