Targeting Tires

When it comes to tire management, Ken Still will tell you that a fleet's ability to save or lose money hinges on one person: the truck driver.

“You really have to be on top of tires in this business,” says Still, the maintenance manager for Nashville-based U.S. Trucking. “Tires are typically your fleet's second-biggest cost, with fuel your number-one expense and employee wages at number three. So to save money for your fleet, you have to start with tires.”

Still should know. A 17-year trucking industry veteran, he won the Tennessee Trucking Assn.'s maintenance professional of the year award in 1998. He is responsible for all the maintenance on U.S. Trucking's 50 vehicles and trailers, which haul steel products throughout the lower 48.

Still believes drivers play an absolutely critical role in helping preserve, or ruin, a fleet's tires. “They are with the equipment every day, so the easiest thing they can do is check the air pressure in each tire on their truck,” he says. “If they get on a daily program with you and make sure those tires are properly inflated, that's a real big help in preserving tire life.”

Industry experts agree wholeheartedly with Still's assessment. “I can show fleets a simple way to save big money on their tires — simply have their drivers check the air pressure every day,” says Guy Walenga, engineering manager for Bridgestone/Firestone Tires Sales.

“Even if they paid someone to do nothing but check the tire pressure on every truck and trailer they owned, they'd save more than enough money through extended tire life, reduced wear and blowouts to pay that person's salary — and then some,” he notes.

According to the Rubber Manufacturers Assn. (RMA), over 321-million automotive and truck tires were sold in the U.S. last year, up 1.4% from the record 316.6-million units sold in 1999.

Though RMA says the softening U.S. economy and cuts in both the light-vehicle and truck production schedules will result in decreased tire sales this year, the group expects a turnaround starting in 2002, leading to growth rates in tire shipments of 2% a year through 2006.

After a slight 5-million unit decline in 2001, auto and truck tire shipments are projected to increase overall between 2001 and 2006 to eventually top 350-million units — a projected increase of 35-million tires, says RMA.

According to the Tire Retread Information Bureau (TRIB), retreading tires saves trucking fleets about $2 billion a year. Because 70% of the cost of a new tire is in the tire body, the cost of retreading a tire can be anywhere from 30% to 50% less than buying a new one.

Retreads are already in wide use among truckers. Of the 26.2-million tires retreaded in the U.S. and Canada last year, 6.3 million went on light trucks and 18.1 million went on medium- and heavy-duty trucks.

Many experts believe that the trucking industry loses millions of dollars a year because of poor tire maintenance. Improperly inflated tires, which wear out at a faster rate, are the biggest culprit.

It's actually the pressurized air in the tires, not the tires themselves, that supports the truck and the trailer on the road. The tire is just the container that holds the air.

The Technology & Maintenance Council (TMC) reports that 10% underinflation will shorten a tire's tread life by 9% to 16%. Bridgestone/Firestone points out that if the average tire costs $250, that 10% underinflation costs a fleet $25 per tire. And because you'll change tires more often, you'll pay more in tire service fees, along with downtime.

If underinflation exceeds 10%, warns Bridgestone/Firestone, a fleet may have even bigger problems. Flat tires and emergency road service calls due to flats can cost anywhere from $100 to $1,000. Both TMC and RMA also recommend that tires that are underinflated by 20% (or more) be immediately removed from service and inspected for damage.

That's just the beginning. Imagine bending the sidewall of a tire with your hands 500 times a minute. A truck tire goes through a full revolution, flexing all the way around, about 500 times per mile. At 60 miles per hour that's 500 times a minute. Tire engineers call this flexing “deflection.” With underinflation, there's even more deflection, which consumes more energy and uses more fuel. Underinflation by as little as 10 psi will probably impact fuel economy.

In addition, excessive deflection weakens the steel cords within the tire. And even if things don't go that far, flexing can generate too much heat, which damages the tire's casing. This affects retreadability. If a fleet's casings are worth $60-$80, instead of getting a useful retread, the fleet may have to dispose of the tire — losing $60 to $80, plus the $3-$7 disposal fee required by most states, according to Bridgestone/Firestone.

The composition of the rubber itself, combined with the kind of operating environment trucks are subjected to, means that the tires can lose up to 2 psi per month through diffusion alone. Consequently, tire makers urge fleets to check tire pressure regularly; it's the first line of defense against the problems related to underinflation.

It's also important to keep wheels clean and properly lubricated, as well as make sure valve stems and cores are in good condition.

Finally, quality metal valve caps are a must. In addition to serving as the primary seal against valve leaks, caps help prevent dirt and water from entering the mechanism, says Bridgestone/Firestone. A valve core is a mechanical device that must seal at very high pressures. If a tiny bit of dirt gets in, it can prevent proper sealing. Just as water can freeze and crack concrete, it can also freeze inside valve stems, disrupting the seal.

TMC estimates that it takes about 20 minutes to check and adjust inflation pressure on an 18-wheeler. According to Bridgestone/Firestone, doing this kind of maintenance only once a week can go a long way toward preventing underinflation problems. The benefits? Increased uptime, better fuel efficiency, longer tread life and improved retreadability — all of which can put money back into a fleet's pocket.

All of these issues are important to U.S. Trucking's Still, whose staff of six mechanics handles every aspect of maintenance on the fleet's 50 tractors and trailers, from oil changes to engine rebuilds.

The spread axle design of the fleet's trailers — critical to hauling steel products — puts a beating on tires, says Still. And because the trailers are equipped with air-ride suspensions, drivers dump air pressure prior to tight turns to try and prevent the trailer's tires from rolling under or sliding — a situation that eats tires up.

Dual tires, especially on the trailers, are a major concern for Still. He says trailer tires, especially the inner dual, have to be checked the old-fashioned way, with an air gauge, not the billy clubs he sees some drivers use to thump tires. “That only tells you if they're inflated or flat, not if they're underinflated,” he notes.

Another issue is the dual tires that don't match in diameter. The smaller tire will be dragged along by the larger one. That can result in extremely rapid and irregular wear on the smaller tire. If duals differ in inflation, their diameters can differ enough to cause this kind of problem, Still points out.

He says one serious concern he has is when the inner tire on a pair of duals is underinflated or flat. “That means the outer tire carries the entire load. It will get even hotter than normal and could blow out on you,” Still says. “And you don't ever want that to happen, especially when you're hauling a load of steel.”