The Service You Deserve, The Quality You Expect

The physics and chemistry behind your tires

September 10th, 2015

Manufacturers have to look at three basic elements when designing a tire: seal, structure and tread

Tires may look simple, but they’re actually very complex.

By: Jil McIntosh for Metro, Published on Tue Sep 08 2015

At first glance, tires look pretty simple: They’re just round and black. But they’re actually very complex, consisting of numerous layers and specially-formulated rubber compounds.

“The purpose of the tire is to provide the braking, accelerating and cornering capabilities to make the vehicle go where the driver wants,” says Ron Margadonna, senior technical marketing manager for Michelin North America. “It’s the only component of the vehicle that touches the ground.”

Tire manufacturers have to look at three basic elements when designing a tire. The first is the seal so that it holds air, which includes an inner liner made of composite rubber. The only thing holding the tire onto the rim is air pressure, so it’s imperative that the tire seals properly.

Next is the structure, including the sidewall, which gives the tire its strength. Finally there’s the tread, which has to grip the pavement.

The compound used to make the tread is composed of such materials as natural and synthetic rubber, oil, silica and carbon black, which gives it its color. Rubber chemists create different formulas, depending on how the tire will be used. Summer tires need a firmer compound that won’t get too soft in hot weather, while winter tires need to stay supple in cold temperatures. All-season tires use a compound that’s approximately halfway between the two.

The tread’s design is a vital part of the tire, and engineers have to ensure that it’s the right pattern for the job. “The grooves are for foul weather such as rain or snow, everything but dry,” Margadonna says. “The grooves channel the water away. If it was always dry, you wouldn’t need them.”

The pattern creates blocks of tread, which determine how the tire will perform. Winter tires will typically have numerous small blocks, which create more sharp edges to bite through snow, while high-performance tires will have large, strong blocks to stay rigid during hard cornering.

The edge of the tread is called the shoulder, while the small slits running through the tread are called sipes. These spread open as the tire touches the road, providing even more gripping surface.

The tread eventually wears down with use, and so tire manufacturers mold in small rubber bars, called wear bars, which run across the width of the tire’s tread. They’re deeply buried on a new tire, but they become easier to spot as the tire wears down. If the tread has worn enough that you can quickly spot the wear bars, then it’s time to replace the tire.

Tire care

• Keeping your tires properly inflated can help save gas. A vehicle uses about 20 per cent of its fuel energy just to overcome the rolling resistance of its tires.

• The recommended air pressure is on a label inside the driver’s door, while the number on the tire is the maximum it can hold.

• Run-flat tires can support the vehicle’s weight even when they’re flat, and cars that have them don’t have spare tires.

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