Tire Maintenance for Equipment and Work Trucks
Heavy loads and long roads - here's how you make sure you get the most out of your tires.
The expense of purchasing a tire for work trucks and various other equipment speaks volumes about the engineering and materials involved in the tire's production.
Off-the-road tires support heavy equipment that carry large loads at higher speeds and over long distances. Work conditions endured by off-the-road tires can be extreme, with weather ranging from very cold to very hot and various types of driving surfaces that can test service life of the tires.
Maintaining the service life of an off-the-road tire involves keeping the tire properly inflated, awareness of how driving surfaces and conditions impact tire life, and checking daily for cuts, abrasions, and damage to the rims. Good operational practices can increase the durability and capability to resist hazards seen with the new generation off-the-road tires.
Basic Anatomy of Heavy Equipment Tires
Tires consist of the tread, the carcass, breakers, the bead, and the sidewalls, regardless of whether an excavator, skid-steer loader, dozer, or work truck has bias, bias/belted, or radial tires. Because the tread establishes traction, tread type depends on the site conditions and the application of the equipment. The carcass contains the inflation portion of the tire and must have the strength to contain the tire pressure. Bias and bias/belted tires use many angled plies of fabric for the carcass, while radial tires use one ply of steel wire.
Breakers, or belts, fasten the carcass to the tread. Along with joining the two parts, breakers also distribute road shock, establish the optimum tread impact, and add resistance to penetration. Bundles of high-tensile strength wire, called beads, anchor the tire to the rim. Bias and bias/belted tires feature several bead bundles, while radial tires have only one bead bundle. The sidewalls resist cuts and protect the tire from weathering.
Maintain the Proper Deflection and Load/Pressure Relationship
Engineers design off-the-road tires for optimal performance at a given deflection. The term “deflection” indicates the change in tire radius with the application of a normal load. The unloaded radius of a tire occurs when the tire is inflated to its working pressure, mounted on a rim, supported, and touching the ground. The static-loaded radius measures the impact on the tire under the weight of the vehicle and the vehicle's payload.
Deflection equals the difference between the two measures and the distance that an axel lowers under a full load. For example, after earthmover carries a full load, deflection will be noticeable with a bulge at the bottom of tire.
Deflection becomes important when considering the load/pressure relationship of a tire. Operating a heavy equipment tire with too little deflection shortens the service life of the tire. Thus, the design of a tire and the amount of deflection depends on the relationship between the specific load rating and specific pressure rating. This relationship also factors in the speed of the vehicle.
Maintain Proper Inflation
The inflation of a tire determines the load amount a vehicle can carry. In turn, the pressure capacity of the tire depends on the 'ply rating' for bias and bias/belted tires and the 'star rating' for radial tires. Some off-the-road tires may include symbols that indicate the maximum load carried by a tire at a maximum speed.
An under-inflated tire causes overloading, which leads to tread and ply separation. If the condition continues, the carcass will begin to tear apart and the sidewall will crack. Driving an overloaded excavator, with over inflated tires to compensate for the load, will cause impact cuts and lead to rapid wear of the tires. This condition causes the fabric that makes up the carcass to break down.
Proper tire inflation occurs with a cold reading and requires the tire to be idle for at least 24 hours. A cold reading should occur once a week, with hot checks occurring daily. Even though normal equipment operation causes tire inflation to increase, it's important never to bleed air from a hot tire. Clean any debris from the valve stem and record the inflation during each check. The correct tire inflation yields the best load carrying ability and avoids damage to the carcass and treads.
Check for Damage and Use Good Driving Sense
Regular maintenance preserves the service life of an off-the-road tire. Check the tires at the beginning of each shift and, during inflation, check for cuts that touch or extend into the belts or cords. Clean any lodged or embedded debris from shallow cuts. If left in place, debris as simple as a rock can drill through the cord body.
When traveling between work locations, operators will need to use lower speeds. Traveling at higher speeds generates internal heat that can separate the treads. Never exceed the load capacity of the tires. During work, avoid tire spin that can also generate heat within the tire. Instead, use hydraulics to crowd the work material. When possible, operators should use the bucket to clear and smooth the driving path, as rough surface conditions can damage excavator tires