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Chapter 19: Off-Highway Tires
November 1, 2007 By: Pit and Quarry Staff Pit & QuarryTires play a major role in any quarry's productivity and, ultimately, its profitability. Simply by knowing and observing simple basic tire facts and techniques a quarry can make a noticeable difference in the life of its tires and the performance they deliver while in operation. Choosing the correct tires for the application, maintaining those tires through proper maintenance techniques, and educating machinery operators about tire basics are just some of the ways that a quarry operation can realize significant savings and uptime.
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The importance of a proper understanding of tires and their place in any operation cannot be underestimated. Any quarry that ignores its tires and the significance of their proper selection, maintenance, and usage is virtually guaranteed to encounter tire failures, downtime and a significant loss to its bottom line.
Choosing the correct tire
Not every tire is capable of optimal performance on every surface or terrain. Some tires are capable of operating adequately in multiple applications, but most tires are designed to deliver the best possible performance based on the requirements of a specific application. That is why it is vital to know, as accurately as possible, what demands the quarry's terrain will make on the equipment and its tires. This knowledge will greatly help when deciding which tires to fit on equipment.
As part of the tire-choosing process, another issue to consider is whether the equipment will be used primarily off-road, on-road or an even mix of both. To be classified as off-road, a specific piece of machinery would generally spend at least 80 percent of its operation time off-road, with only 20 percent of operation occurring on-road. The opposite is true to be classified as on-road—80 percent of operation on-road, with 20 percent coming off-road. Some equipment may truly be considered on-/off-road, if its operation time is spent almost equally between applications. It is important to know this information, because the use of the tire will determine what rubber compounds in the tread are recommended, as well as the tread depth and tread design. An on-road tire is engineered differently to be optimized for road travel, with more attention to using softer rubber compounds, shallower tread depth and less aggressive tread designs. Off-road tires will feature more robust sidewalls, harder compounds and aggressive treads to guard against damage, provide increased traction and handling and evacuate debris or stones from the tread.
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When deciding between radial tires and bias-ply tires, there are some important factors to be aware of. In the 1940s, almost all construction, mining and quarry equipment ran on bias-ply tires. A bias-ply tire is made up of textile plies, usually nylon or rayon, crisscrossed on top of one another and bonded together by a rubber compound. This design is prone to damage from poor heat conduction and punctures. In addition, sidewall distortion can lead to uneven wear and reduced adhesion between plies.
In 1959, Michelin brought radial tire technology to the heavy equipment market. The biggest difference between a radial and a bias-ply tire is that the sidewall of a radial is separate from the crown, allowing each component to work independently, thereby enhancing performance. In a radial tire, metallic casing plies hold the sidewall and the crown together, reinforcing the strength of the tire. In addition, the metal allows for greater heat dispersion and impact resistance. Since the sidewalls can flex independently of the crown, a radial tire maintains a consistent contact patch and offers exceptional operator comfort without compromising stability and performance.
"To improve upon the radial design, modern radials incorporate a special butyl rubber layer that eliminates the need for a tube in the tire," said Todd Ramsey, director of replacement market sales for Michelin North America's Earthmover division. "Tubeless earthmoving tires provide several advantages by eliminating the risk of puncturing the inner tube and also the risk of air becoming trapped between the tire and the inner tube.
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