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Roll With It

Tires represent one of the largest cost areas for fleets but that also means they offer one of the greatest opportunities for cost savings. The challenge is to work smarter not harder in finding those...

Tires represent one of the largest cost areas for fleets but that also means they offer one of the greatest opportunities for cost savings. The challenge is to work smarter not harder in finding those savings.

It’s well known, albeit not as well followed, that working smarter begins with proper tire inflation. A radial tire casing carries about four per cent of the overall load while the air inside the tire carries the remaining 96 per cent. Regularly running tires underinflated or overinflated will result in early failure.

“Eighty five per cent of the alligators that you find on the side of the road died there because of poor inflation management,” says Goodyear’s Gary Blake.

The second most important step to maximizing your tire investment is proper selection. That requires taking into consideration the type of operation your truck tires run in, the average speeds and axle weights they are subjected to, as well as any special operational complications.

“No matter how good your preventive maintenance program is, you can’t realize the best performance for your tires if you don’t select the right tires for the application,” says Bridgestone/ Firestone’s Brian Rennie.

Most tire manufacturers use the following breakdown when looking at operating conditions:

Linehaul: Trucks running 200 or more miles on four-lane highways with gentle curves and grades are in true linehaul applications. In such cases a tire’s rolling resistance and its ability to combat irregular wear are among the most important considerations. Tires with side grooves will control the forces acting on the shoulder ribs and add flexibility to the shoulder area to cut down on irregular wear. The more aggressive tread designs, although they may provide greater traction or damage protection, will have a higher rolling resistance and lower fuel economy. When looking at the profile of the casing, remember that the width of the wires and how they are twisted together to form a cable come into play in determining how much energy is required to roll a tire. One of the more common mistakes is using P & D-specific tires in linehaul applications, particularly when a local-delivery fleet secures new business a little further afield. The sidewall protectors in tires designed for P & D operations make for more rubber working under hotter conditions. The end result is increased fuel consumption.

Regional highway/P&D: Smaller highways have more aggressive road surfaces and turns and require a different type of tire. Trucks on such runs may also be delivering loads within the heart of major cities. The right tires for such applications have protective elements built into the sidewalls and shoulder area to resist highway abrasion and the shocks of sidewalk scrubbing and going over curbs. Also look for a drive tire pattern that is aggressive enough to provide traction at loading docks with ramps.

On/off road: Consider your fleet in this category if your trucks spend between 20 per cent and 50 per cent of their miles off road. Chips and cuts from large, jagged rocks form the main threats to tire life in this application. Look for a tire with proven stone ejection features and a high level of resistance to chips, cuts and stone drilling. It will need an extra structure within the belt package to protect the casings and the substructure of the belts.

Off road: If your trucks are spending up to 80 per cent of their time off road you must consider serious tread depth – up to 40/32nds. Also look for a split-belt design that provides more give in the middle of the tire.

Other key operational issues to consider include cabover vs. conventional designs (long-nose conventionals, particularly those with 250-inch to 280-inch wheelbases, place very little weight up front and so are more prone to irregular wear); axle positioning; and engine horsepower. The higher the horsepower the greater the torque applied to the drive tires.

One item that fleets neglect at their peril is matching tires’ rated speed against the speeds the fleet’s trucks are allowed to run. Truck speeds have been creeping upwards since the mid- 1990s. There are now 40 U.S. states that have posted truck speeds of 65 mph or higher – 22 more than in 1995. And that move to higher speed limits is having a spillover effect north of the border, even if the posted speed limits haven’t been changed.

Bridgestone/Firestone’s Rennie said that a random survey of 688 trucks in the U.S. found that 20 per cent were running over the speed limit, 17 per cent were regularly at speeds over 75 mph and some at speeds as high as 100 mph.

Yet high speeds take a terrible toll on tire life.

Almost eighty per cent of fleets surveyed with trucks running at higher speeds reported a drop in tire durability; 60 per cent complained of irregular wear; and 78 per cent reported higher tire costs associated with higher speeds.

Rennie outlines what happens when a truck running with tires spec’ed at 65 mph starts regularly doing speeds of 75 mph: As the operating temperatures increase so does the likelihood of damage such as rib tearing. The footprint also becomes distorted leading to irregular wear. And while rolling resistance remains the same the tire’s contribution to overall energy loss is cut in half.

“Most of the benefit of a fuel efficient tire is wasted,” Rennie explains.

The problems associated with higher speeds don’t stop there. There are also weight penalties to consider. Tires rated at 65 mph and running 10 miles faster require a 12 per cent decrease in load weight and a five per cent increase in inflation pressure. Over the last couple of years tire manufacturers have responded to the higher speed trend with drive and steer tires rated at 75 mph but many trailer and on/off road tires remain rated at 65 mph.

Once the operational issues noted above have been taken into consideration you’re ready to choose your tires. Always keep in mind that quality is worth paying for.

“The quality of the product at every step needs to be addressed. Even small fleets can lower their cost per kilometre by using a quality product,” says Ralph Beaveridge, marketing manager, truck tires, for Michelin’s Canadian operations. “There are definite benefits that come from buying a better casing. It may be more expensive up front but the casing will prove its value over time. The value of a casing is in how long it will last in its first life, its second life and, potentially, its third life.”

Also, don’t neglect to consider some of the less common specs. For example, conventional tire sizes make up about 75 per cent of commercial tire purchases but low-profile tires have their advantages, according to Rennie. They provide weight savings that can be used to increase load capacity and “with a more stable footprint they can theoretically provide less regular wear and extended tread length.” Some fleets also report that low profiles improve fuel economy. However those advantages must be balanced against the fact low-profile tires can be more susceptible to sidewall damage and that they may not be available when you need them because they’re a less common spec.

The next key ingredient to findings savings in your tire program requires a commitment to casing management. Bandag’s Tom Coutu says that means working out standards for the age of your tires, tread depth at which they’re pulled off for retreading, the amount of times you’re willing to have them retreaded, the type of repairs that should be done to them and figuring out which brands offer the best retreading potential. Coutou adds that many fleets are missing out on a chance to get the most out of their tire program by retreading their drive tires to the trailer position. He says if drive tires are retreaded back to the drive position first and then to the trailer position, the average life of the casings is kept down and mileage is increased.

“If you’re not retreading your tires into drive you’re throwing money away,” he says.

The final piece of the puzzle is tracking tire performance. As Coutou puts it, you don’t have a tire program unless you have informat

Tracking tire performance can involve two approaches: a point-in-time survey to indicate how a fleet’s tire program is performing at a specific moment; and a long-term survey that tracks selected tires over a long period of time, advises Goodyear’s Blake who adds that tire sales is evolving from a business based on relationships to one based on performance facts and data.

Armed with such information, you can determine if your fleet is running the right tires for the application; compare the on-road performance of different tire brands, gauge the effect of different drivers, vehicles and operating conditions on tire life; and better understand the effectiveness of your tire maintenance program and removal procedures.

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