Tires: Closing the gap

Sept. 1, 2007
Fleets have traditionally faced a tough choice when selecting tires: Go with one that produces fuel savings or one offering long tread life. They couldn't get both in the same package, forcing them to manage the tradeoffs as best as they could. That need to compromise may disappear as tire makers develop new tread designs and rubber compounds that will narrow the gap between those alternatives. You

Fleets have traditionally faced a tough choice when selecting tires: Go with one that produces fuel savings or one offering long tread life. They couldn't get both in the same package, forcing them to manage the tradeoffs as best as they could.

That need to compromise may disappear as tire makers develop new tread designs and rubber compounds that will narrow the gap between those alternatives. “You still face that tradeoff today, but it's at a different level than in the past,” says Don Baldwin, product-marketing manager for Michelin Americas Truck Tires.

Typically, a tire designed for fuel economy featured a vertical solid-block tread for low rolling resistance, while one geared for better traction and extended life had a lot of open siping and a zig-zag tread pattern. According to Baldwin, however, Michelin's new “matrix siping,” combined with a hybrid vertical/zig-zag tread design, delivers a 400,000-mile tire that offers a good fuel economy footprint, too.

“It doesn't give you the optimum in terms of fuel savings, but its fuel performance is very good,” he explains. “It's all about splitting the difference. Open siping in a tire gives you better grip and allows the tread to be more mobile, improving its wear characteristics. Yet when tread is mobile like this, it uses more energy, thus its lowering fuel economy benefit. [We are trying] to get the best from both worlds into one tire.”

Curtis Decker, national manager of field engineering for Continental Tire North America, addresses the issue of the tire compound itself. “The tread pattern, tire casing and steel belt design all play a role in getting there, but the real magic is going to happen in compounds,” he contends. “That's where the lion's share of the improvement is going to come from.”

In Decker's view, how the rubber physically interacts with the road is the key to getting both optimum fuel economy and long life. “This isn't simple, because road surfaces vary tremendously, from hard to soft, rough to smooth, wet to dry, etc., [and] road surface really affects tire performance,” he says. “If it was easy to design a tire that gives you everything, we'd have cracked that egg a long time ago. We're definitely getting closer to having it all, but we're still not all the way there yet.”


Tractor-trailer application adds a huge wrinkle to the tire selection process, and in some cases forces fleets to commit to long-life tires simply because more fuel-efficient designs can neither deliver fuel savings nor hold up under the strain. Tires are also designed to be axle specific, as each axle — from the steer and drives on a tractor to those on the trailer — exerts very different forces.

“Application is an extremely important part of the tire selection process from the start,” says Tim Richards, Goodyear Tire & Rubber Co.'s project manager for long-haul commercial tires. “Most of the fuel economy benefit you'll get from tires comes predominantly in highway driving. But if you're operating in a stop-and-go environment and making a lot of turns, you need a tire built to withstand those conditions. You are not getting up to the speeds where fuel economy becomes a bigger factor.”

“When you're running around a city all day, going from store to store and dock to dock, such as in LTL or pickup and delivery (P&D) operations, you're not in a fuel-efficient environment to begin with,” adds Greg MacDonald, engineering manager for Bridgestone. “You need a tire with strong sidewalls and deep tread to resist scrubbing up against curbs and such. Those aren't the characteristics of a fuel-efficient tire. In this [application], fuel economy is not as big an issue as durability.”

Kumho Tire USA's segmentation of its commercial products exemplifies how the tire industry addresses the significant differences among truck operations. The tire maker says its linehaul tires are designed to resist uneven wear and provide long tread life while carrying constant loads typically driven long distances on highways at sustained speeds.

Regional tires, on the other hand, are designed for varying loads, vehicle speeds and distances on both highway and secondary roads, while improving stability, handling and traction.

P&D tires, which are made for short trips at slow variable speeds (0 to 50 mph), with a lot of stop and go plus turning, offer good traction and a resistance to sidewall damage.

Mixed service tires are designed for both on- and off-road work and come in three distinct types: light duty (85% on-road, 15% off-road), medium duty (55% on-road, 45% off-road) and heavy duty (15% on-road, 85% off-road).

The off-road designation is reserved for tires spending almost 100% of their time in off-road conditions, such as coal mining or rock quarrying, where exposure to severe cut, chip and tearing of the tread are major issues. Tires must be specially designed and compounded to survive in these conditions.

Last is a “catchall” category for tires that don't really fit in any truck classification, such as high-capacity trailer tires.


Axle position is also a major consideration when deciding which type of tire to use. “All tires are designed to be axle-specific,” says John Cooney, director of commercial sales for Yokohama Tires. “You have to build tires to standards that are specific for each position on the tractor-trailer due to the different forces in play,” he explains.

Cooney points out that steer tires typically have a pretty brutal life. All the turning and engine power they're subjected to means they usually have to be replaced around 150,000 miles, which is anywhere from a year to a year-and-a-half of operation. Drive tires can last longer, 350,000 to 500,000 miles, because they don't deal with all the turning stress. That's about three years of operation — usually the length of a for-hire fleet's trade cycle, assuming the tires are maintained properly.

Trailer tires, which log about 20,000 miles annually, are “free rolling,” meaning no power is applied through the axle. Thus, they are designed with a relatively shallow tread.

“It's key to have the right tire in the right position,” Cooney says. If the tread is too shallow or too deep for a specific axle position, you'll end up with excessive wear and a shorter than expected life cycle.

It's also why creating a one-position-fits-all “vanilla” tire isn't practical adds Bridgestone's McDonald. “We'd end up with a tire that only offers mediocre performance in both categories, unable to please fleets seeking fuel economy or longer tread life,” he says. “That's why we're still going to have distinct tire types.”


The bottom line for fleets, though, is to spec tires that will be cost-effective, whether in terms of fuel economy, tread life, or both.

The key to making the numbers work is to analyze the data for your fleet, rather than relying on general comparisons, which can't account for critical operational differences, McDonald explains. “Every fleet is going to be different; I can't stress that enough,” he says.

“Fleet A can't use the same exact tires as fleet B and expect the same savings because their operations are different. That's why you need to measure and track your own tire performance,” he emphasizes. “You don't want to jump blindfolded into any tire change unless you know exactly how it will affect your bottom line.”

One generalization that McDonald is willing to make, however, is that for OTR carriers, spec'ing tires for fuel economy is usually going to offer the biggest rate of return. “Typically, the more expensive fuel gets, the more bang for your buck you get by switching to fuel economy tires,” he notes. “Again, though, you must run a tire evaluation to confirm that it works out for your fleet.”

Yokohama's Cooney backs up McDonald's cautious approach. “You have to study all aspects of your operation to prove the potential for savings,” he explains. “In some cases, using deeper tread drive tires might cost you fuel economy on the front end, but as that tread gets shallower, they become more and more fuel efficient,” he continues. “If you get 20% more life out of them at that fuel efficient ‘sweet spot,’ does that translate into more savings overall for your fleet compared to using fuel economy tires at the start?”

In terms of life cycle value, Michelin's Baldwin says tire OEMs are shooting for some pretty high targets. Assuming that fleets take good care of their tires — keeping them properly inflated, with truck and trailer axles balanced and aligned so tires don't wear unevenly, for example — they should be able to retread their casing two or three times. Since new tires cost almost twice as much as retreads — on average, a new truck tire costs between $250 and $350 per unit, while a retread costs between $72 and $120 per unit — that's big money over time.

“That's where mileage comes in,” Baldwin points out. “The number of miles you put on a tire affects the casing, and that subsequently affects retread life. If you take care of the casing through proper maintenance and don't run down the original tread too much, you can get three retreads out of that tire. Then you are looking at a million-mile life cycle for a tire, which is really good life and value.”


However, Continental's Decker points out that when fuel prices increase, more immediate savings become available to fleets in position to benefit from tires spec'd for fuel economy.

“Tires represent 35% of the overall fuel economy picture for a typical tractor-trailer,” he notes. “That 35% breaks down like this: steer tires are responsible for 13%, drive tires 49%, and trailer tires 39%. So the biggest impact on fuel economy comes from tires put on the drive and trailer axles, respectively.”

From there, the savings can get pretty dramatic, depending on fuel prices. A truck that runs 120,000 miles per year getting 5.5 mpg will burn 21,898 gallons of fuel annually, says Decker. And if fuel prices average $2.89 per gallon, that totals $63,054 in fuel for one truck for one year.

“If you go with fuel economy spec tires on just the drive axle, you can improve fuel economy around 4.5% or so. That saves you over $2,881 in fuel per year,” he says. “Figure you are buying eight drive tires at $350 per unit — and that's at the high end — to achieve this fuel savings. That costs you $2,800,” Decker points out.

“Not only do you recoup that money in one year from the fuel savings, you'll have those tires on the drive axle another two years minimum, effectively putting over $5,700 back in your bank account,” he points out. “Extrapolate that over an entire fleet of just 100 or so trucks and you can see how such savings add up in a hurry.”


And this is just the tip of the fuel economy iceberg. Goodyear introduced a new line of fuel-sipping tractor and trailer tires last year, the Fuel Max line, which combines a new rubber compound and tread design for improved fuel economy. Based on rigorous SAE fuel economy tests, Goodyear demonstrated at its San Angelo, TX, proving grounds that these new tires can improve overall fuel economy by a minimum of 4%.

A 4% gain for a truck averaging 6 mpg translates to 6.24 mpg, says Jon Bellissimo, Goodyear's director of technology for commercial tires. Assuming 120,000 miles a year and a diesel price of $2.85/gal., using Fuel Max tires could save a fleet $2,100 per year, per truck. That far outweighs the 4% to 5% higher price premium Fuel Max tires have over the company's current OTR tire, he adds.

Michelin's Baldwin points out that similar improvements can come from using his company's X-One wide base tires on the drive axles, but with a 4% gain over the best fuel economy tires. Michelin's calculations show a fuel savings of $2,400 per truck per year for a tractor-trailer clocking just 100,000 miles annually.

That's the part of the value equation OEMs are ultimately trying to achieve by combining fuel economy and long tread life specs into one tire package: Tires that not only pay for themselves, but also save fleets serious money over their life cycle.

“CSI” for truck tires

With freight volumes stagnant or falling and operational expenses rising, fleets are doing everything they can to keep a tight rein on expenses. That includes managing their second-largest expense on the balance sheet — tires — more closely than ever.

To improve tire management, Goodyear is joining forensic-like investigative techniques with detailed data gathering and tracking systems. According to the tire maker, issues can now be identified in real time and fleets can evaluate the data immediately.

“We used to focus solely on products — new tires and retreads — when we talked to fleets about cradle-to-grave tire solutions,” Roy Sutfin, general manager-service for Goodyear Commercial Tire Systems, told Fleet Owner. “Now we're focusing on all the service touch points in the tire chain. In addition to products, we're improving our services and data management for fleets. It's all about figuring out what the tire is telling us about the truck and how it's operated — and how to use that information to save the fleet money.”

The first piece of that puzzle comes from a more detailed physical inspection of the tires, the truck, and the trailer, not unlike a CSI (Crime Scene Investigation) approach. Goodyear's new “Fleet Solutions Bootcamp” hammers home deeper analytical tire inspection skills as part of a five-day course for tire sales personnel at the Goodyear Commercial Tire Academy in Dallas.

“Being a good tire detective tells you if problems are related to the tires or to the truck and trailer,” explained Sutfin. “Excessive tread wear on one side of the tire could indicate the axles are out of alignment or the wheel bearings are failing. Heel-toe wear highlights a tire-balancing problem or maybe improper inflation. That kind of knowledge, communicated in real time, lets the fleet take corrective action so it can run its business better and save money.”

Scrap tire analysis — going over a tire corpse as it were — is critical to gaining vital information that will assist the fleet in driving costs down, said John MacMullin, regional director for Wingfoot Commercial Tire Systems, Goodyear's service center subsidiary.

“The key is tracing a tire to the vehicle, and we use our TV [tire value] tracking system to do that,” he told FleetOwner. “Each tire is ‘fingerprinted,’ telling a fleet which truck or trailer it came from and its position. Was it a drive or steer tire? Inner or outer dual? That way we can provide value-added information quickly. The problem is identified and the solution provided in minutes. The process helps fleet owners to lower their cost per mile, saving them money over the life of the vehicle.”

About the Author

Sean Kilcarr | Editor in Chief

Sean previously reported and commented on trends affecting the many different strata of the trucking industry. Also be sure to visit Sean's blog Trucks at Work where he offers analysis on a variety of different topics inside the trucking industry.

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