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Summary
  • Tires are made of natural and synthetic rubber, steel, textiles, fillers, and other ingredients.
  • Rubber possesses traction, cost-effectiveness, and viscoelasticity that make it suitable for car tires.

What are car tires made of? While most people know that tires have lots of rubber, they also contain other materials that contribute to their performance. They even have two different types of rubber. If you know what tires are made of, you can take better care of them, extending their lifespan and helping them maintain their performance.

What Are Tires Made Of?

Natural Rubber

Tires are mostly made of natural rubber. Made from latex sap gathered from rubber trees, it comprises 28 percent of a typical car tire’s weight. The tire tread combines natural and synthetic rubber, but the sidewall uses only natural rubber for its superior flexibility.

Many of the characteristics we associate with tires come from their high natural rubber content. Natural rubber resists cracking and tearing, allowing tires to last longer.

Synthetic Rubber

Synthetic rubber is an artificial polymer produced from petroleum byproducts. In car tires, the artificial polymer is either used with natural rubber or alone.

Butadiene rubber and styrene butadiene rubber are the most commonly used synthetic rubber in car tires. Together with natural rubber, they make up the tire tread.

Since synthetic rubber polymers comprise a considerable percentage of the tire’s overall weight and the tread, they play a significant role in determining how the tire performs. For example, they set the rolling resistance, the energy required to keep the tire spinning.

Synthetic polymers also determine how fast the tire tread wears out. They also affect traction, the ability of the tread to grip the road surface.

Butyl rubber is another major synthetic rubber found in tires. Also called halobutyl rubber, it’s used in the inner liner, which regulates tire pressure by preventing air from escaping the inner chamber. This part needs an impermeable material like butyl rubber to ensure the tire stays inflated.

Synthetic rubber is also used in the tire’s bead apex. The bead apex works together with bead reinforcement to orient the tire in the direction set by the steering system.

Steel

Believe it or not, tires contain steel. Steel wires run through the tire belts below the tread. Similar wires are also part of the tire beads. The belt wires make the tire casing stiffer, reduce wear, and improve handling on the road. Meanwhile, the bead wire anchors the tire, locking it onto the wheel.

Textiles

Tires also contain textiles like aramid, nylon, polyester, and rayon. Woven into fabric cords, textiles strengthen the tire. They also provide dimensional stability, increasing the stiffness of the material. Finally, they help bear the vehicle’s weight.

Tire plies are made of textiles. The tire casing’s main strengthening material, tire plies also help maintain the tire’s shape no matter how rough the road gets. Using textiles in tire plies increases this part’s endurance and performance.

Carbon Black and Silica Fillers

Fillers increase the strength of rubber, improving its tensile strength and resistance to damage. Two of the most commonly used tire fillers are carbon black and amorphous precipitated silica. Silica filler enhances rolling resistance. Meanwhile, carbon black gives rubber tires the color that we’re familiar with.

Antioxidants

Antioxidants protect rubber from degradation caused by temperature and exposure to oxygen. They increase the lifespan of the tires.

Antiozonants

Not to be mistaken for antioxidants, antiozonants prevent the ruinous effects of ozone on the tire’s surface.

Tire Curing Ingredients

Tire curing is a chemical process that converts natural rubber into a solid material. Also called vulcanization, it adds sulfur and zinc oxide to improve the process. These ingredients accelerate the curing process.

Sulfur and zinc oxide also determine how many crosslinks form in the rubber matrix and how long these crosslinks can grow during the curing process. Crosslinks connect the polymer molecules, preventing rubber from melting when it’s hot and becoming brittle when it’s cold.

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Why Are Car Tires Made Of Rubber?

Tires continue to use rubber to this day. But what makes rubber such a good material for tires?

Traction

The first reason is traction. Tires must grip the road surface and maintain contact even when things get slippery, such as when it rains or snows. Thus, they need to be made of a material that increases traction.

Rubber tires have excellent traction on multiple levels. Vulcanized rubber is adhesive on a molecular level, allowing it to stick to driving surfaces.

Next, rubber enables the creation of surface textures on the tire tread during molding and curing. These rough textures can latch onto similar parts on the driving surface, creating additional traction on a microscopic level.

Finally, rubber tires have the flexibility to adjust their body and shape around obstacles, increasing the surface area in contact with the road surface. They also have sipes that can channel slippery mud, snow, or water to improve traction even more.

Cost and Lifespan

Rubber is cheaper than other materials with similar properties. Furthermore, synthetic rubber usually costs less than its natural counterpart. That’s why modern tires contain far more synthetic rubber than natural rubber.

You can increase rubber’s performance by adding relatively inexpensive ingredients like sulfur. Thanks to these enhancers, rubber tires can last for many years, especially if you take good care of them.

Viscoelasticity

Rubber is viscoelastic. In layman’s terms, it acts like a viscous liquid and an elastic spring simultaneously, especially when it encounters stress.

When you apply stress to rubber, the material will keep flowing at a reduced rate. Think of how a rubber tire partially deforms around a hard object, such as when it rolls over a small rock or presses into a parking block.

At the same time, rubber is elastic. It can stretch when stressed. Once the source of stress goes away, rubber springs back to its original form. Of course, if you exceed its limit, rubber can snap from the strain.

Modern tires combine rubber’s viscoelasticity and the properties of compressed air, leaving older, solid rubber designs in the dust. Rubber tires can bear considerable loads, enabling larger vehicles with greater cargo capacity. They also maintain good traction on the road surface while cushioning heavy loads. At the same time, rubber tires apply less pressure on the road. Furthermore, they help dampen noise while driving, leading to a quieter and more pleasant drive.

About The Author
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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