Needed pressure

Always check a tire’s pressure when the truck has been parked for at least three hours to get the proper “cold inflation pressure.”

Today, black is green. With soaring diesel prices, the once oft-neglected tire is getting more attention as an area for improvement to save on costs.

Reinforcing the idea that being green makes both economic and environmental sense, tire manufacturers have branded their campaigns and products as such. These include Goodyear’s Fuel Max Technology product line and Yokohama’s Z.environment line. Continental Tire North America offers the HDL Eco Plus tire, and Michelin, along with its “Go Wide, Go Green” promotion, has the XDA Energy tire.

But the easiest way to maximize cost savings from any tire is to keep it properly inflated for the load it helps support. “Proper inflation is always important to assure that you are getting the handling and wear performance from your tires, but in today’s environment of high fuel prices, it is especially important,” says Don Baldwin, product manager for Michelin Americas Truck Tires. “Tires that are running underinflated have more rolling resistance than tires that are properly inflated. High rolling resistance equates to poor fuel mileage and higher fuel costs. It also equates to higher greenhouse gas emissions.”

On average, if you’re not keeping up with tire inflation already, doing so can yield as much as a 2- to 3-percent gain in fuel mileage. But some drivers have chosen to overinflate, reasoning that it will improve fuel economy even more. Overinflating can have serious repercussions.

“Although this would result in even lower rolling resistance, there begins to be a series of negative affects if the tire is overinflated,” says Tim Miller, Goodyear Tire and Rubber’s commercial tire marketing communications manager. “The most critical is the fact that the tire and wheel could be inflated beyond their strength capabilities, with catastrophic results.”

According to Bridgestone Firestone North America Tire, tires should always be checked and adjusted for proper inflation when the tires are cold (rule of thumb – when the tire has been parked for about three hours). This is because rolling on the highway heats up the tires and increases the air pressure inside the tires. For instance, a tire inflated to 100 pounds per square inch at 70 degrees Fahrenheit can rise to 110 to 115 psi during normal operation.

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Ambient or outside temperature also affects tire pressure. The inside air temperature of a properly inflated tire can increase more than 50 degrees F above the ambient temperature during normal working conditions.

When the tire sits for about three hours, the “contained,” or inside, temperature of the tire equalizes. Because tire engineers take these variables into consideration when they design the tire, adjusting the tire pressure of a hot tire – one driven for more than a mile – could result in the tire being underinflated.

It is important for drivers who drive from extremely hot temperature regions to cold areas or visa versa to adjust their cold-tire pressure for proper inflation, which also increases the life of the tire, minimizing irregular wear; longer tire life means a decrease in tire cost per mile.

“Proper inflation means the tire is inflated to a pressure that corresponds to the load it is carrying,” Miller says. “At that load and inflation pressure, the footprint of the tire on the road surface is exactly what the tire designer intended, and the tire has the best chance to wear evenly.”

It becomes even more important for the future retreading of the tire’s casing (see “Retreads: New Lease on Life,” at right).

“Inflation pressure higher or lower than the optimum will cause the footprint to change and can lead to abnormal or rapid wear,” Baldwin says. The excess heat produced, in turn, “will reduce the life of the casing and make it less likely to be retreaded.”

Tire design also figures greatly into the quest for lower rolling resistance, which is basically the drag produced by the tire’s contact with the road. A tire’s footprint, which depends on tread depth and width, along with inflation, determines its rolling resistance. The goal of tire manufacturers in producing lower rolling resistance is to increase fuel savings without compromising tire life, traction or safety.

Of course, new wide-base singles have gotten a lot of attention as a solution to the problem of lower rolling resistance. Michelin, with its X One series, and Bridgestone, with its Greatec, were the first two manufacturers on the market. Some major manufacturers are in the development stage with their own wide singles.

“Because an X One tire has only two sidewalls instead of the four sidewalls of the duals it replaces, it has inherently lower rolling resistance and therefore better fuel mileage,” Baldwin says. “In addition, it is lighter, which allows the trucking company to carry more load per truck and therefore reduce the number of loads it has to run.”

Bridgestone says its Greatec is as fuel efficient as other wide-base tires, but it also offers conventional tires that are just as fuel efficient. It says the biggest benefit of its wide single is weight savings for trucking applications where weight reduction can impact the bottom line.

Scrap Tire Uses
Once a tire is deemed unfit for retreading, it doesn’t necessarily end up in a landfill, which has become a huge environmental concern.

Among the uses:

  • Entire homes can be built with tires by ramming them full of earth and covering them with concrete. The end products are known as Earthships.
  • Artificial reefs, like the Osborne Reef Project in Fort Lauderdale, Fla., are built using tires that are bonded together.
  • The process of stamping and cutting tires is used in some apparel products, like footwear, and in road sub-bases by connecting the cut sidewalls to form a flexible net.
  • Ground and crumb rubber from old tires can be used in both paving-type projects and in moldable products. These types of paving include rubber-modified asphalt and rubber-modified concrete as a substitution for an aggregate. Examples of rubber-molded products include carpet padding or underlay, flooring materials, dock bumpers, patio decks, railroad crossing blocks, livestock mats, sidewalks, rubber tiles and bricks, moveable speed bumps and curbing/edging. Plastic and rubber blend also can be used for molded products like pallets and railroad ties.
  • Athletic and recreational areas like basketball courts can be paved with the shock-absorbing rubber-molded material. Rubber from tires is sometimes ground into medium-sized chunks and used as rubber mulch.
  • Ground-up tires often are recycled for use in new car products like exhaust hangers, brake pads and shoes and acoustic insulation.

Retreads: New Lease on Life
To get the maximum benefits of a tire, retreading an original tire casing not only lowers the overall cost of ownership but also has environmental benefits.

According to the Tire Retread & Repair Information Bureau (TRIB), the cost of a retread is 30 to 50 percent less than a new tire. If an original tire is properly maintained, the casing often can be retreaded up to three times.

“The more times a tire is retreaded, the lower the cost per mile of operation,” says Harvey Brodsky, managing director of TRIB. In North America, more than 50 percent of all new tires sold are retreaded at least once. This represents in aggregate more than $3 billion in savings for truckers and fleets.

On the environmental side, the savings are just as impressive. According to Bridgestone Bandag Tire Solutions, it takes approximately seven gallons of oil to retread a truck tire compared to the 22 gallons required to manufacture a new tire. The energy needed to retread a tire also has been estimated at roughly 70 percent less than manufacturing a new one.

While retreading a good casing would seem a no-brainer for cost-savvy drivers, some truckers don’t trust the reliability of retreads. TRIB says this perspective is faulty.

“Retreaded tires perform as well as tires that have never been retreaded, and they do it at a tremendous savings over the high cost of new tires,” Brodsky says. “Every reputable truck tire manufacturer, with no exception, designs its truck tires for multiple lives, meaning the tires are designed to be retreaded. There is an abundance of evidence which proves the safety, reliability, performance and superior handling of today’s retreads.”

According to TRIB, virtually every commercial airline in the world routinely uses retreaded tires on even their largest passenger jets. Thousands of school buses, municipal buses, trucks, taxis, racecars and millions of motorists safely use retreaded tires. Retreads also are safely used on emergency vehicles such as fire engines and ambulances.

In addition to misconceptions about the reliability and performance of retreads, the age-old myth that most rubber debris (or gators, as many truckers like to call it) found on the nation’s highways comes from retreads is ultimately false, too.

“Many people automatically assume that all tire debris comes from retreads,” Brodsky says. “Yet much of it comes from tires that have never been retreaded. Underinflation by far is the biggest culprit. Overloading, mismatching of duals, improper alignment, failure to stop when a tire begins to lose air: These all cause tires to fail. And it doesn’t matter if the tire is a retread or a virgin casing. If it is abused long enough, it’s going to fail.”