There's quite a history behind the way vehicle tires have improved during the past century. If you drive a popular passenger vehicle here in the United States, it probably has radial pneumatic tires. This type of tire became popular in this country in the 1970s. Before that, bias-belted tires dominated the market.
Removable, air-filled (pneumatic) tires first appeared on vehicles in Great Britain in the 1920s. These so-called balloon tires were an upgrade from solid rubber tires. The early pneumatic tires were made with bias or bias-ply technology. These tires became the industry standard for all automobiles and were constructed for passenger use, commercial transport, and even farm tractors. As additional tests were run and tire technology pushed to heed the call of automotive advancements, changes were made to the construction of tires in order to gain better performance and efficiency. Along came bias-belted tires.
The bias tire is the predecessor of the bias-belted tire. Bias tires have a tire bead (the area that holds the tire against the rim when it's inflated), a sidewall, and tread just like any other tire you've seen. The difference in bias tires is what is found beneath the tread-the inner workings of the tire. In order to support the vehicle and maintain form when filled with air, bias tires have a series of tire plies under the tread. A ply is a layer of material, such as nylon or steel, that offers internal support when mixed into the layer of rubber underneath the tread. "Bias" means that these plies are layered diagonally.
Bias tires were developed in order to offer a smooth and resilient ride on rough surfaces, but they also possessed immediate drawbacks, most notably a high rolling resistance. Rolling resistance is the amount of tire resistance that your vehicle has to overcome in order to roll forward. When your vehicle has to put up with more rolling resistance from your tires, it has to use more gas. In an effort to address the drawbacks of bias tires, bias-belted tires were developed and incorporated into many vehicle designs. Still with us?
Bias-belted tires are still on the market today. They are manufactured similarly to the original bias tire. The difference comes after the bias plies have been layered. Above the top layer of tire ply, stabilizer belts, generally made of steel or other corded material, are applied at different angles to the plies, offering additional support and a stiffer inner material to bond with the tread.
Bias-belted tires provide a smoother ride and lower rolling resistance than bias tires do. Bias-belted tires are popular with people who drive classic cars and who prefer to keep the equipment as close to original as possible. Bias-belted tires are also manufactured for some light trucks such as pickup trucks and SUVs. While they still serve some purposes, when talking tires for the average modern vehicle, bias-belted tires can't compare to the performance capability and efficiency of radial tires. Radial tires give vehicles lower rolling resistance, higher mileage, and a more comfortable ride.
SimpleTire.com recommends using tires that meet the original equipment specifications of your vehicle. You can find this information in your vehicle owner's manual.
Maintaining and Caring for Bias-Belted Tires
If you do own bias-belted tires, just like all tires, they must be properly maintained in order to offer optimal performance and sustain maximum tread life. Regularly checking and maintaining air pressure is one of the easiest and most important aspects of tire maintenance.
When you check pressure, also look for uneven treadwear, shoulder wear, or sidewall damage. Rotating the tires every 5,000 - 6,000 miles will ensure that they're able to offer their maximum tread life. Unlike radials, bias-belted tires can be rotated from front-to-back and side-to-side, as well as diagonally. Ask the service professionals at your dealership about the best ways to care for the bias-belted tires on your vehicle.
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