How Tires are Made

Tires are a sophisticated mix of materials, including high-tech fabrics, natural and synthetic rubbers and even steel.

Running along the inner edges of a tire are the beads. Beads are high-strength steel, coated in rubber, which gives tires strength while also helping to hold the tire to the wheel. The body of the tire is actually made up of fabric, not rubber. The body is built from layers of fabric (each layer is called a ply). The plies aren't your run-of-the-mill cotton fabric; they're usually a strong composite material. The plies are coated with rubber, not only to help them hold air inside, but also to help them bond to the other parts of the tire.

For steel-belted radial tires, on top of the body are steel belts. These belts help make the tire relatively immune to punctures (since most nails and other road hazards aren't getting through steel) and they also help keep the tire tread, which is actually making contact with the road, at the optimum level of flatness. Keeping the tread's shape just right ensures more road contact, which means more traction and control.

Up to now we've only talked about how tires are built from bottom to top. But the sides of a tire are also important. The sides of a tire are called its sidewalls. It's here that information about the tire is printed and some tires have even have white or red sidewalls, just because they look cool. But, aside from looking good and providing information, the sidewalls help hold the parts of a tire in place and give the tire stability during side-to-side movements.

The final part of the tire is the tread. The tread is on the outer edge of the tire. Like the sidewall, it's made of a mixture of natural and synthetic rubber. Whereas the sidewall is relatively smooth, however, the tread has a series of grooves in it. Each grove serves to maximize performance and safety, whether a tire sports deep grooves for going off-road or just a few shallow grooves for hitting the track.

Now that you know what goes into a tire, keep reading to find out how it's all put together.

Actually putting all the parts of a tire together can be a messy process.

Rubber either coats or is the primary material in most of the parts of a tire. But the rubber used in tires isn't pure rubber; it's a mix of rubber (both natural and synthetic), oils and additives. Before a tire is built, all those components for the various rubber parts of the tire are mixed together in a banbury mixer, until they have the consistency of gum. From there, the material is sent to other machines, where it's fabricated into the individual parts of a tire.

Once all the tire parts are made, they get sent to the tire building machine -- which is a pretty apt name. On the machine goes an inner liner of rubber, the plies, the belts, the bead, the sidewall and the tread. Once all the parts are in place, the tire building machine presses them together.

The tire isn't finished yet, however. When a tire comes off the tire building machine, it's what's called a "green" tire. The materials have been put together, but they haven't cured. Plus, green tires don't have the grooved pattern of the tread in them yet.

Green tires go into a mold, where they're inflated. Inflating the tire causes it to press against the mold. As a result, the mold imprints the tread pattern and tire information on the tire. While in the mold, the tire is heated to over 300 degrees Fahrenheit (149 degrees Celsius) to cure the rubber and bond the components. It stays over that temperature for about 15 minutes for passenger car tires -- bigger tires, like truck tires, may cure for an entire day. The heating process is known as vulcanizing the tire.

From there, the tire gets inspected. Then it's ready to go on your wheels.

Most people don't have to buy tires too often. Tires today are built to last for around 50,000 miles (80,467 kilometers), so many people get new cars long before they get new tires.

If you buy a new car, odds are that the tires came from one of eight companies. In fact, eight tire companies provide the tires for all of the new car market in the United States. Michelin has the largest share, with Michelin tires going on 29 percent of new cars sold in this country.

If you're keeping your car and need new tires, you'll need to go to a tire shop or dealer. In 2009, 182 million replacement tires were sold in the United States. However, if you buy new tires for your car, you're no longer limited to the eight brands that most car companies buy tires from dealers. Of course, each tire brand makes specialty tires for every use imaginable, from track cars to rock crawlers, heavy-duty trucks to Smart cars.

And, making and selling tires can be fairly lucrative. In 2009, Bridgestone America sold $8 billion worth of tires. If you're buying new tires, the prices can vary quite a bit. The average retail price of a low-cost radial tire was about $75 in 2009. However, performance tires can cost hundreds of dollars.

Now, however, when you look at a tire's price, you won't just see the dollar amount. You'll see the parts, technology and assembly that went into building what puts the rubber on the road.

For more information about tires and other related topics, follow the links on the next page.