FACT SHEET - Radial Tires vs. Bias-Ply Tires
Two basic types of tire construction are bias-ply and radial. A tire's construction is the key to its performance; and outstanding tire performance is a key competitive advantage for transport and working machines in the earthmover industry.
BIAS PLY
Construction
The bias-ply tire is made of layers of rubber-coated plies composed of textile cords, usually nylon, placed upon each other at approximately 30-degree angles. These plies are then wrapped around the bead wires - which anchor the tire to the rim - to form the casing, or air chamber. The plies are then covered with more rubber to form the tread pattern.
Performance
The only way to increase the strength of bias-ply tires is to increase the number of plies and bead wires. More plies means more mass, increasing heat retention, reducing tire life.
The bias-ply tire casing is constructed to form one working unit. When the sidewalls deflect, the tread squeezes in and distorts. This makes the tire scrub or squirm, decreasing traction, operator control and accelerating tread wear. Since the tread is subjected to any flexing that occurs, the footprint, or contact patch, distorts. This distortion causes abrasion from the ground surface, which reduces the life of the tire. All of these factors significantly increase fuel consumption.
Bias-ply tires have reduced life due to fast wear, high fuel consumption and reduced grip and control.
RADIAL
Construction
The radial tire is constructed in two parts. First, a single layer of rubber-coated steel cables arch from one bead to the other to form the tire casing. Second, numerous rubber-coated steel belts are placed in the crown, under the tread, to form a strong stabilizing unit.
Performance
To increase a radial tire's strength, larger diameter steel cables are used. These steel cables help reduce punctures, tears and flats. They also help distribute heat, resulting in a cooler running tire, improving fuel economy.
The combination of steel stabilizing belts and the single-layer radial casing allows the tread and sidewall to act independently. The sidewall flexes easily under the weight of the vehicle and its cargo, while the tank-track type tread provides even contact with the ground. Greater vertical deflection is achieved with radial tires. This is desirable because extreme flexing greatly increases resistance to punctures while protecting the operator and expensive vehicle components.
The stabilizing steel belts and radial construction minimize tread distortion. As the sidewalls deflect, the belts hold the tread firmly on the ground, minimizing tread scrub and greatly increasing tread life.
When negotiating curves and encountering side forces, the independent action of the tread and sidewalls keeps the tread flat on the road. This allows the tire to hold to its path.
Studies of highway use demonstrate the effectiveness of radial construction. Independent road tests* showed the radials made lane changes on wet pavement 10 percent faster; stopped in a 21 percent short distance; ran 27 percent cooler and negotiated curves 15 percent faster. These proven performance results are why trucks and automobiles use radial tires.
Summary
Earthmoving equipment can achieve outstanding performance by using radial tires.
Radial tires for transport and working machines deliver longer life, have significantly fewer flats and provide better traction, all of which result in more uptime for machines compared to those equipped with bias-ply tires.
Other radial advantages include low fuel consumption, improved operator comfort and machine operation due to increased sidewall deflection. Radials also lower a machine's center of gravity, which improves stability. This results in more productivity from equipment on the job site.
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