As discussed in Part 1 of this series, a well-informed, well-defined tire maintenance and replacement strategy can enable fleet managers to save time and money, while decreasing downtime and increasing productivity. This strategy should include a plan for tire selection, repair and, when necessary, replacement.
The OTR tire industry has come up with nomenclature that makes the selection process for tires easier for buyers: E is for earthmover, L is for loader and G is for grader. However, Bill Porterfield, regional off-the-road (OTR) manager for Titan Tire Corporation, indicates there is more that must be considered in the selection process.
"The two major things you want to consider beyond tire type are compound and tread design. Choosing the right compound and tread design will mean better performance and longer tire life," says Porterfield. "The tire dealer should make recommendations on each, based on the operational and site assessments."
Porterfield goes on to explain that a cut-resistant compound would be good for rough applications where the machines are traveling at low speeds and short distances. Conversely, a high-speed haul application that is traveling longer distances would be better off with a heat-resistant compound.
Tread design is also critical to performance and tire longevity. Along with the E, L and G nomenclature, comes a number from 1 through 5 that describes the tread depth, with 5 being the deepest.
"The deeper the treads, the more resistant those tires will be to punctures from sharp objects. So, for a loader running in an extremely rocky, harsh terrain, an L-5 would offer the most protection," explains Porterfield. "An L-5 may be overkill for less harsh settings, however, which is why it is important for the tire dealer to conduct a site assessment and determine what is most appropriate."
Furthermore, proper tire selection is based on operational factors such as distance, speed and load to determine adequate load capacities and ton-mile-per-hour (TMPH) ratings. The tire dealer will often suggest changes in operations in order to avoid premature tire fatigue. These recommendations, however, may require some compromise from the fleet manager.
"After the operational assessment, the tire dealer may conclude that the fleet's TMPH exceeds the limitations of the tire. When this happens, the tire dealer will often recommend traveling at lower speeds, running fewer cycles or carrying smaller loads," says Porterfield. "Such a suggestion is often hard to swallow for fleet managers, however. In the end, the tire dealer can consult with the fleet manager to decide which provides a greater cost savings — increased tire life or increased production."
In terms of regular maintenance, Porterfield stresses that monitoring inflation pressures is the most important task in prolonging tire life.
"Paying proper attention to inflation pressure can extend tire life by anywhere from 5% to 30%," says Porterfield. "So, I would recommend checking inflation pressures daily, before the machine has been started and is still cold."
He adds that problems with operator abuse can be diminished with the installation of pressure sensors. "With today's in-cab monitors, it's getting easier for operators to spot problems before they escalate," he notes. "If an operator realizes that a tire is even just 10 psi below where it should be, that should be cause for concern. Catching a problem early on could mean the difference between replacing a $40 valve and replacing the whole tire."
The strategy for tire rotation will depend on the individual machine. "For a three-axle haul truck, about 55% to 65% of gross vehicle weight is carried by the front tires when empty, so it's important to rotate the fronts to the rear at about one-third of the tires' expected life spans. When loaded, however, approximately one-third of the weight is distributed to each axle, so it's also important to look at how operational and site conditions affect tire wear in order to make a rotation recommendation," Porterfield states. "On a loader, you have to keep in mind that the front tires usually bear 65% of the load with a bucket attached. So, it's really important to rotate front to rear in order to give the front tires a rest for the remaining 50% of their projected life."