Every tire tells a story. Flat spots can identify aggressive brakes, wear on the inside of both steer tires can indicate a toe-out of the steer axle, and the feathering on the edge of a rib can be an ...
Every tire tells a story. Flat spots can identify aggressive brakes, wear on the inside of both steer tires can indicate a toe-out of the steer axle, and the feathering on the edge of a rib can be an early sign of alignment trouble.
It can be a costly tale.
Once the driver is paid and the tanks are filled with diesel, the next-highest operating cost for most fleets is found where the rubber meets the road. And according to Bandag, 47% of dispatched roadside assistance calls are caused by tire-related failures; half of those could have been avoided with preventive maintenance programs.
But a careful eye to tire condition can lead to decisions that will extend tread life and maximize the opportunity for retreads.
About 10% of your rolling stock should be used for learning about new equipment and comparing different technology, suggests Michelin marketing director Ralph Beaveridge. “I tend to look at fleets above 50 units as being big enough to manage that sort of thing.”
The target is to look at tire choices in terms of a cost per kilometre. From there, you can determine whether a casing that cost 25% less at the time of purchase loses the price advantage after repairs, downtime, and lost retread opportunities are considered.
That information comes by feeding inspection details about everything from tread life to casing condition into software programs such as Goodyear’s TVTRACK, Bridgestone’s Market Profiler, Michelin’s eTire System (which reads information from a chip embedded into truck tires), or turning to services such as Bandag’s Tire Management Solutions.
For any inspection program to maximize tire life, however, it also has to correct problems found along the way.
“Truck tires can lose up to 2 psi of inflation pressure per month, even if they’re brand new and properly mounted,” says David Scheklesky of Bridgestone/Firestone Canada. More air can escape if the bead isn’t completely clean or properly coated with lubricant during mounting.
And low pressures are known tire killers.
The continual air loss enforces the need to check pressures on a regular basis. Those who sell the rolling rubber suggest it’s best to put a gauge to every valve on a daily basis, but that isn’t always feasible since such a check on a tandem-tandem takes about 20 minutes.
Linehaul operations should check inflation every week, while those working in mixed service applications — exposing tires to off-road hazards — should check it more frequently, says Goodyear technical marketing manager Al Cohn. And every pre-trip inspection should still look for signs of physical damage.
Temperatures also have to be watched, since a 10F shift in temperature can mean a 2 psi drop in pressure.
It’s an area where driver incentives can pay off. Consider that Goodyear has discovered that a highway tire that’s under-inflated by 20% will also have its life shortened by 16%, coupled by a 2% drop in fuel economy. Some fleets pay drivers a bonus based on spot inspections; others run contests to stoke the competitive instincts among those at the wheel.
Checks are also more likely if drivers don’t have to twist off a valve cap to apply the gauge, so flow-through valve caps are growing in popularity. “We end up with quite a bit of work in the on/off road field, and the wheel assemblies are often filthy,” says Greg Cressman, Yokohama’s deputy technical director. “Just getting to the valve stem, the risk of jamming a valve open and losing the air pressure, that’s something we fight against.”
And don’t forget to supply the $20 tire gauge that makes the reading possible in the first place.
An alignment check at the first sign of irregular wear can be another affordable action to extend tire life.
A three-axle alignment check will typically cost less than $90, while an alignment involving just a few shims will cost $300 to $400, says Cressman. (The price increases if you have to replace tie rod ends or ball joints.) Consider the payback, he adds: “You’ve got 10 tires there at an average cost of $4,000.”
According to Goodyear, a fleet that introduces its first alignment program can increase tire life by as much as 30%.
Some fleets will run steer tires in drive positions until they wear down by 1/32 to 2/32 of an inch, to establish a good wear pattern, the manufacturer adds. And since the rear tires on a tandem will often wear out faster than those in forward positions, drive tires should be rotated from front to back at least once before retreading.
It’s also important to ensure temporary repairs don’t become permanent, says Eugene Johnston, Bandag’s manager of process development. Larger injuries need patches that are heat-cured in a curing chamber, or with a sidewall spotter that applies heat and pressure in a localized area. “It’s not the type of thing that gets done at 10 at night or on a weekend. That’s when a tire usually gets a nail hole.” And that’s when patches are attached with chemical compounds.
It can also pay to remove treads before they wear down to their minimum depths, he says, adding that many fleets will pull drive tires once treads reach 6/32 of an inch. That leaves less chance of a damaged casing, and plenty of traction for slick conditions.
Still, it’s also important to know when to step back from the numbers, and make changes in smaller steps.
Fleets that push casings to 13 years of service will sometimes drop to four years’ worth of retreads at the first sign of trouble, says Bandag’s Johnston. A reasonable life might fall somewhere in between, thanks to improvements in compounds that fight oxidation and ozone exposure.
“The most common spec’ing mistakes can involve over-reacting.”