Picture a NASCAR driver pulling into the pit, currently in first place. The pit crew swaps out the tires for a set of underinflated deep-lug off-road tires. How do you think that driver will do the second half of the race? Not only will the car quickly fall behind, but the tires will probably blow out in minutes.
It’s an extreme example, but it shows the importance of proper tire selection and maintenance. For construction equipment, those tire selection and maintenance choices can have a similar impact on vehicle performance and operating costs. Just as important, particularly in the larger production machines, is wheel selection and maintenance. With a few tips on wheel and tire selection and maintenance, equipment owners can make sure their vehicles perform when needed and that their profitability is maximized through lower cost of ownership across the entire fleet.
Today’s Small OTR Tires: Selection Based on Surface
A number of tire design characteristics determine how well a tire will perform in different applications, including tread pattern and tire construction (radial or bias). These characteristics can greatly impact tire longevity. Here are some considerations by equipment type.
Skid Steer Tires
When evaluating skid steer tire tread patterns, there are three types to choose from: diamond, bar (also known as swept) or turf (also known as button) lugs.
A pattern featuring diamond lugs and small voids performs best on hard surfaces such as rock and concrete. As a deep tread design that puts more rubber on the ground than a bar lug design, it still offers good traction when needed, but it offers the best in wear and impact resistance for skid steers primarily working on hard surfaces.
If working in deep mud and areas where traction is a concern, choose a swept/bar lug design. The swept/bar lug design features bar lugs that overlap toward the center of the tire and expand with larger voids toward the shoulder of the tire. The large voids provide excellent traction on soft surfaces and also allow the tire to better clean itself when transitioned onto a hard surface.
Turf/button lug patterns are similar to diamond lugs, but they feature extremely shallow treads with little void space between them. This design is best used in applications where turf disturbance is a concern, such as landscaping on a golf course.
Determining where and how a backhoe will be used is a key consideration when selecting tires. There are two tread style options for front backhoe tires – an I-3 or F-3. The open-bar lug design of an I-3 provides better traction on soft surfaces. The ribbed design of an F-3 provides longevity, durability and a smooth ride on hard surfaces.
When choosing a rear backhoe tire, you should evaluate the tire’s lug-to-void ratio. Tires with a higher lug-to-void ratio are typically better for hard surfaces with a more stable, smooth ride and long, even wear. However, these tires wouldn’t have as much traction in mud, snow, and sand as a tire with a low lug-to-void ratio. Tires with a low lug-to-void ratio are better for gaining traction on soft surfaces, but they could wear more quickly and cause a rougher ride on the road. For those that work on both hard and soft surfaces, choosing a happy medium is often the best option for all-around performance, such as a tire with a high lug-to-void ratio in the center and lower lug-to-void ratio toward the shoulder.
The construction of the rear tire is also a factor. When selecting bias or radial, consider how often you tram your machine. If your machine is consistently running longer distances or at high speeds on hard surfaces, a radial tire may be the best option. If you are working short distances, a bias tire might be sufficient. While radials outperform bias in many instances (justifying the increased cost), bias tires, when used in the proper application, can provide significant cost savings and performance benefits.
There are two main types of tread styles offered for graders. If you are using a grader for gravel road grading, a directional tread design with a center riding rib is a good option. This is used for hard rock and abrasive surfaces where traction and even wear is needed.
The other style is an all-season tread pattern used for plowing snow, key for traction and self-cleaning on all surfaces.
When choosing between a radial or bias grader tire, it again depends on the application. If you are tramming long distances, a radial would be best. However, a bias tire is often sufficient and can save you money if used properly.
Earthmoving and Large OTR Tire Selection
If your fleet has larger earthmoving machines, tire purchasing decisions should be looked at with a critical eye. Tire overheating, puncturing or tread separation could all occur as the result of an ill-chosen tread pattern – and in a production environment, downtime is lost money.
The Tire and Rim Association (TRA) has made letter and number designations for treads that apply to all tire manufacturers. The letters E, G and L represent the intended use of the tire, while the number indicates the tread depth. Each of these letters is followed by a number that denotes tread depth and style.
E, G and L
Earthmover (E) is designed for haulage and transport of materials on unimproved surfaces at up to 40 mph and up to 2.5 miles at a time.
Grader (G) is designed for grading material over unimproved surfaces at speeds up to 25 mph and for unlimited distances.
Loader (L) is designed for use on loaders and dozers that do not exceed 5 mph and distances of 250 feet each way.
Tread Depth Numbers
1 – Rib tread with standard depth for earthmoving (E) applications primarily on roads.
2 – Traction tread with one-to-one lug-to-void ratio and a standard tread depth for E, G and L applications that require traction on soft surfaces.
3 – Rock tread with two-to-one lug-to-void ratio and a standard tread depth for E, G and L applications in average hard-surface conditions.
4 – Rock tread with a two-to-one lug-to-void ratio and tread that is 1.5 times deeper than standard for E, G and L applications in harsh, rocky conditions.
4S – Smooth tread pattern with no lugs and a tread that is 1.5 times deeper than standard for L applications on hard surfaces where traction isn’t a concern.
5 – Rock tread with a two-to-one lug-to-void ratio and tread that is 2.5 times deeper than standard for L applications in the most severe working conditions.
5S – Smooth tread pattern with no lugs and a tread that is 2.5 times deeper than standard for L applications in severe working conditions that require wear-resistance over traction.
7 – Rib pattern with a shallow tread that is 60 percent as deep as standard for E settings where flotation and minimal ground disturbance is required.
Smooth-tread tires, offered in L-4S and L-5S tread depths, have the most amount of tread rubber for protection in severe applications, which don’t require traction and long tramming, such as scrapyards and landfills. More traditional basic bar lug designs are also offered in E- and L-style tires, as well as various tread depths based on application.
Loaders are a great example of where the choice of bias versus radial can make a big difference in lifetime cost per hour. If a loader is running in an application, such as working at the face of a muck pile, where the machine is only traveling short cycles at low speeds, digging into a pile and loading a truck or crusher – a bias could be an excellent, low cost-per-hour investment. Alternatively, if a loader is traveling at full speeds, with a loaded bucket, tramming across a jobsite – a radial is going to be a better, long-lasting investment.
Haulers (Rigid and Articulated)
In hauler applications, radial tires are primarily used because of the high-speed, long-distance nature of the work. However, there are some nuances to earthmoving radial tires that should be considered, including TMPH ratings and tread compounds. TMPH stands for ton-mile-per-hour and is a rating that determines a tire’s ability to withstand the load, speed and distance of the hauling. It’s incredibly important that hauler tires have sufficient TMPH ratings for the machine and haul route.
Compounds are also important for both large loader and hauler applications. For radial tires, they fall into one of three categories. Cut-resistant (C) is formulated for protection from chipping and tearing in rocky applications. Wear-resistant (W) is formulated for extending tread wear in load and carry applications with frequent stopping and starting. Heat-resistant (H) is formulated for haulage applications with heavy loads, long distances and high speeds.
Inflation and Rotation
Maintaining proper inflation pressures is the best way to prolong tire life. It’s best to check inflation each time the machine is being refueled, at minimum. It’s also important that the fleet manager inflate to the tire manufacturers’ recommended levels for each individual machine. Rotation schedules should be determined by individual machine.
Repair Versus Replace
Additionally, you should know when to replace versus when to repair. A good rule of thumb is to consult your tire dealer on all repairs. If a tire is running low on tread, but is still holding air and is structurally sound, it may be a good candidate for retreading. Pull that tire off with about 15 percent of the tread remaining. If it goes much further than that, and any of the under-tread compound is exposed, it’s too late.
Don’t Forget the Wheels
With so many choices in the selection of tires, it’s easy to forget about a critical component of the assembly – the wheel. One of the latest advancements in wheels is quick-change technology, also known as Accelerated Change Technology (ACT) or Quick Change Rims (QCR). These quick-change technologies allow the inner tire of a rigid haul truck to be removed without having to remove the outer wheel. On a complete tire change-out or whole-truck rotation, using a quick-change technology can reduce associated downtime by up to 50 percent – an investment that could boost production by $1 million per year with a fleet of 15 98-ton trucks hauling coal.
Wheel maintenance often takes a back seat to tire maintenance, but fleet managers should realize wheels are equally as important. A daily machine inspection should include observing the overall profile of the tire and wheel configuration. This means looking for any signs of corrosion and examining component parts such as the rims, flanges, lock rings and driver keys. It is also important to look at the valve stem, caps and core. If any part of the valve is malfunctioning, there is potential to lose air pressure.
With more application-specific tire options available than ever before, it’s never been more important for a fleet manager to understand how to strike the perfect balance to get the most of their investment. Making an informed decision will ultimately lead to increased productivity and longevity of your tires, but only if you understand the options available.
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