To achieve optimal tire life and operating costs, select tires to match both the application and operating conditions.
The recent shortage of earthmover tires has taught contractors a lot about the role tires play in the overall cost of doing business. "The tire shortage that plagued the industry for the previous years has lightened significantly," says Cara Junkins, director of sales and marketing, Titan. "During that time though, a lot of operators learned how to watch tire costs and do what was necessary to elongate the life of their tires."
Even though the shortage for certain sizes is beginning to ease, the influence tires have on overall operating costs remains, since they greatly affect fuel costs, productivity and vehicle performance. "Site operators who are looking to increase their overall profitability can do so by taking an easy, yet often overlooked step ? taking care of their tires," says Steve White, earthmover market segment manager, Michelin North America, Inc. "Well-maintained tires allow machines to stay operating longer, increasing productivity and profitability. Not to mention that properly maintained tires help increase safety."
Select for conditions
Fuel has always been near the top of the expenses list. To help control these costs, it's important to understand the role tire selection and maintenance play in fuel economy.
"Fuel economy is all about rolling resistance," says Barry Rexroad, senior manager, OTR engineering, Bridgestone Firestone. "Rolling resistance is basically how freely a tire rolls and how much inertia, or energy, you have to overcome to keep it rolling. It's a little harder to measure in an earthmover tire than it is with a passenger tire because they run on so many different surfaces, such as dirt and mud. How loose or how packed the soil is changes rolling resistance. If the surface is very soft, very rough, etc., it takes more energy (i.e., more power) from that vehicle to keep the wheels turning."
Selecting the right tire for the conditions will help to increase fuel economy, says Junkins. If you run mainly on compacted surfaces, choose a tread pattern designed for that application. If you run mostly in the mud, choose a pattern with extra traction. However, keep in mind that the greater the amount of rubber, the heavier the tire, and therefore, the more energy (fuel) it takes to move it. "Although it plays a relatively small role in fuel economy, it's something to consider," she says. "So don't select a tire with a deep tread unless you really need it."
Maintain proper pressure
While tire design and tire selection affect fuel economy, tire inflation pressure has the greatest influence on rolling resistance. "Tires are designed to work most efficiently at a specific pressure for the necessary load, providing the proper amount of vertical deflection," says White. "A properly inflated tire puts the correct footprint on the ground to provide traction and to reduce wasted energy caused by wheel spin. A properly inflated tire is also more efficient in regards to the energy needed to move the equipment."
Issues arise when tires are over- or under-inflated. "Under-inflation will increase fuel consumption due to increased rolling resistance," says Arve Opperud, Caterpillar, Inc.
"Over-inflation wastes energy by bouncing equipment upward, rather than propelling it forward," adds White. "And it increases energy wasting wheel spin."
Correct inflation pressure is based on load. Work with your local tire dealer or equipment manufacturer to determine the optimum pressure. Essentially, you will want to set the pressure for the heaviest load, then check it regularly, ideally every morning, to ensure the proper pressure is maintained. "You want to cover the situations where the bucket is completely full," indicates Rexroad. "Also consider the density of the material you're moving. If you're unsure, check with your manufacturer and use scales to weigh the equipment with different materials."
Inflation pressures often need to be changed when moving the machine from one application to another, says Blaine Pressley, Volvo. "Volvo lists the recommended pressure by application and tire brand in our operator's manuals," he points out. "It is that important. We also recommend that operators check pressures after the machine has been transported. Tire pressures are sometimes altered to make the machine better for transport, so it's always best to check and adjust as needed."
Pump up longevity and productivity
Inflation pressure also affects tire life and overall operating costs. "Tire pressure maintenance is the No. 1 influence on tire longevity," says Junkins. "If you don't take care of your air, the tire may fail early."
Under-inflation is particularly detrimental. "The structure [of the tire] reinforces it and provides good wear, good traction and holds the air," says Rexroad. "But when it comes to supporting the load, it's all about the air. If there isn't enough, the tire will flex more; that generates heat, which is the biggest enemy of the tire. It degrades the rubber, and the excess flexing shortens tire life. The tire will likely come out of service much earlier than expected."
Too much pressure, however, can stretch the tire and tighten the tread, increasing the chances of punctures. "Over-inflation makes the tire more susceptible to damage from rocks and other debris," says White. The tire doesn't want to 'give' as much and you're more likely to have an object go through it, which can lead to downtime and lost productivity.
Over-inflation also affects operator comfort by reducing a tire's dampening capability. This limits its ability to act as a suspension system, which is especially important on wheel loaders and scrapers.
"Because there is no suspension system on these machines, tire pressure is important," says Rexroad. "When you run over a rough surface, the shock has to go through the tires. Whatever isn't absorbed by the tires is passed on to the equipment, which means more wear and tear on the machine, and also wear and tear on the operator."
In addition, excess pressure produces a smaller footprint to transfer rimpull to the ground. "The wheels will spin and it will be harder to fill the bucket," says Opperud. "Also, filling time will be longer."
The footprint generated by under- or over-inflation can cause uneven tire wear. Under-inflation can promote uneven wear on the outer edges of the tread, while over-inflation causes heavy wear to the center. Either can lead to early removal of the tire from service.
It can also lead to excessive machine vibration, which can hinder productivity. "The steering wheel, mirrors, etc., all begin to vibrate so the operator may let up on the throttle and slow down," notes Rexroad. "Also, if tires on a front-end loader, for example, are severely under-inflated, the machine will sway more when the bucket is raised. Properly inflated tires tend to resist that sway to some degree. But when they are under-inflated, the operator will feel less comfortable because the machine rocks more. He will likely slow down the loading process, and that will slow down productivity."
Match to the task
Improper tire selection can affect tire life and performance, as well as productivity in a given application. Yet, selecting the right tire for the job can be a difficult decision, says White.
"The more severe the application, the more important tire selection becomes to ensure you get the expected performance/production," Opperud states. "If you choose a deep treaded tire for soft sand, you won't be able to fill the bucket because you won't be able to dig. This application would require a completely different tire than what would be required for working in an application such as a rock quarry, where you would need a deep treaded tire with a lot of cut resistance."
To simplify the process, tire manufacturers offer tread depths and compounds to match varying operating conditions and applications. For example, wheel loader tires include L2, L3, L4 and L5. The "L" indicates a loader tire, while the numbers correspond to increasingly deeper tread depths. Earthmover tires follow a similar nomenclature ranging from E2 through E5.
To determine which tire is the right fit, consider ground conditions, cycle times and speeds, traction needs, wear resistance requirements and climate.
"Tread pattern and tire grade affect traction, vibration level, overall comfort and tire longevity," says Pressley. "Using the wrong tread type can cause traction issues, as well as problems with dirt and mud ejection from the tread, and increased vibration in the machine."
If you aren't sure which tire is right for the job, consult with the OEM or tire manufacturer. This can help you avoid a costly mistake.
"There are many examples of improper selection that can 'make or break' machine performance," Pressley points out. For example, customers frequently request L4 or L5 tires for applications where an L3 would perform better and last longer. "Requests for an L5 are often made because of its harder compounds and thicker tread design. This can create a false perception that it will last longer. However, in the wrong application (e.g., high speed, load and carry), the L5 will build up heat faster and wear quicker than the L3. On the other hand, the L5 is a 'must have' tire in the right application.
"The bottom line," he adds, "is that you must have the right tire for the task at hand."
Opperud advises, "Work with your local tire dealer. They will have the local experience to help you achieve the lowest operating costs."