How Are Tires Made?
Sugar and spice and… wait. No, it’s rubber and plastic and high-tech synthetic polymers!
If you’re like us, you spend an unhealthy amount of your precious time thinking about tires. If you’re like everyone else, you probably only consider your tires when they’re causing you problems or when they need to be replaced. But even if they’re the last thing on your mind, tires are a critical component of automotive design that has changed the way we travel in vehicles of all types, so it’s worth taking the time to learn about them.
Throughout the past twelve decades or so, tires and automobiles have come a long way, to say the least. The rubber you drive on every day is similar in many ways to the tires of years ago, but new technology and safety requirements have pushed modern tire design into the fascinating territory. Tires are capable of improving the handling, safety, and ride quality of your car, so the Guides & Gear editors from The Drive are here to help you understand the basics of how they’re made. We consulted the professionals at Michelin to help explain how they're constructed, what they're made of, and how they've changed throughout the years.
Let’s get rolling.
A Primer on Tires
Put simply, tires are rings of rubber that fit around a vehicle’s wheels to cushion the vehicle from the road and help keep it under control. Tires are the only parts of a vehicle that are actually designed to touch the pavement. Though there are many types of tires, the most common for passenger vehicles are pneumatic tires, which are inflated with air or gas to maintain pressure. Most tires today are radial, which means that the cords and internal components are aligned to be perpendicular (90 degrees) with the driving direction.
It’s important to note that tires are not a monolithic group. There are different types, each with a specific function and purpose. Racing tires, for example, are designed to provide maximum grip and cornering performance at the expense of all else (ride quality and longevity, mainly), while passenger car tires are designed to give the vehicle a smooth and quiet ride, good fuel economy, and reasonable safety.
How Did Modern Automotive Tires Come To Be?
Although we can’t go back in time to meet the people who invented the wheel, we do know when modern-style pneumatic tires were first put to use. The first pneumatic tires were developed in the mid-1800s by a guy named Rober William Thomson, but weren't affordable or practical enough for mass production. In 1888, John Boyd Dunlop developed a pneumatic tire for bicycles that is credited as the first widely available model. Though Michelin developed a tire for the automobile, it wasn't durable enough to be sold and didn't take off. It took until 1911 for a tire with an air-filled inner tube to have success.
As everyone preferred some impact protection, pneumatic tires became the norm. Treads were then added in the early 1900s, and tire tech progressed quickly from there, though not without some fairly horrible prospective paths along the way. The DuPont Company developed a commercially viable synthetic rubber in the early 1930s, paving the way for the natural and synthetic mix that's still the preferred method for making tires today.
Since the first tires in the late nineteenth century, tires have been developed for specific applications, including tubeless tires, radial tires, run-flat tires, winter tires, and mud tires, among many others. With the realization that tire production and subsequent disposal or recycling is having a significant and negative impact on the environment, tire manufacturers are trying to shift their focus to ensuring that their tires and the processes that build them are doing as little harm as possible. Tire giants like Michelin, for example, have launched elaborate long-term sustainability initiatives that involve sourcing as many recycled and bio-sourced materials as possible. Michelin says that its modern tires are made from over 200 components and materials and notes that it has invested in an in-house technology incubator to find ways to convert as many of those components to sustainable and recycled materials—certainly a tall task.
Another apsect of that focus on environmental issues has been to turn the topic of a tire’s rolling resistance into a primary focus of development in recent years. For electric vehicles and hybrids, the tires are designed to find a balance between performance and grip and rolling coefficient levels that help improve total range.
Perhaps the most impactful innovation that continues today, however, is the radial tire. Radial tires feature steel belts and plies, which are composed of rubber-coated steel. The plies are arranged radially around the tire and allow for better flexibility, comfort, and efficiency. Before we get into how modern tires are made, though, let's dive into their anatomy.
The Anatomy of a Typical Radial Tire
Here’s the breakdown of the major parts of an average radial tire:
Inner liner: An innertube made of synthetic rubber that maintains the air pressure
Carcass ply: Thin textile cords affixed to rubber that provide structure and support
Lower bead area: Located at the exterior “edges,” this is where the tire holds onto the wheel when rolling over the ground
Beads: Each wheel features two beads, or circular metal wires, that maintain an airtight fit with the rim of the wheel and keep the tire seated
Sidewall: The outside-facing section of the tire that protects it from curbs and other damaging exterior forces
Casing ply: Providing a majority of the strength of the tire, the casing ply is made of up a bunch of tiny metal cords
Cap ply: What Michelin also calls the “zero degree belt,” the cap ply is made of rubber-covered reinforced nylon cords and maintains the tire’s shape while reducing heat
Crown plies: The structural base of the tread
Tread: The tread is the pattern seen on the flat outside portion of the tire. This not only creates traction and grip on the road, it also helps remove any water and dirt from the tire’s surface.
How Are Modern Automotive Tires Made?
In general, the assembly line process starts with mixing and combining raw materials. From there, it progresses through various stages to form the tire and bond various components, such as the treads and sidewalls, together. The final stage involves curing the tires to harden the rubber and set in final details, such as branding and tire size information. Let's break each down.
Depending on the type of tire and its purpose in life, different rubbers, pigments, oils, and additives are selected to create the desired characteristics. This mix ends up being somewhere in the neighborhood of 20 percent natural rubber and 25 percent synthetic rubber, with the rest of the tire being made of metals and other materials. Michelin notes that its tires contain numerous chemical agents that give various tire qualities such as low rolling resistance or ultra-high grip.
Even in today’s automation-heavy world, there are still parts of tire manufacturing that rely on human hands. Michelin says that its tires progress through both hand-made and automated processes, and notes that when necessary, it invents its own manufacturing machines and techniques. Tire production begins by mixing the ingredients together, which yields a homogeneous black mixture of tire goo. Computers monitor and control this process to ensure consistency among the huge numbers of tires being produced. The mixture then moves to other machines to be processed into various tire parts.
Assembly continues when an inner liner is placed inside the tire. Since there are no tubes in modern automotive tires, this air- and moisture-resistant material takes its place. Belts and plies are added next, which are made from steel and other materials. To ensure a tight fit with the wheel, bronze-coated steel wires are added to the tires’ sidewalls. The tire components are placed in position and then pressed together to create “green” tires.
Before curing, tires are called “green” tires, and need to be heated to complete the molding and building process. The tires are placed into a mold and are either inflated or pressed against it, which gives the tire both a tread pattern and sidewall stamping. After the molding is complete, tires are heated to a high temperature—usually 300 degrees Fahrenheit or more—for up to a half-hour. This process vulcanizes the tire, which hardens the rubber and helps cure it. Specialty tires, especially large off-road and heavy machinery tires, can take much longer to cure.
Testing and Quality Control
Tire manufacturers each have their own proprietary testing methods, but the process sometimes involves grabbing a random selection of tires rolling off the assembly line. The tires are tested on the road, cut into to check for consistency and imperfections, and x-rayed.
FAQs about How Tires Are Made
You’ve got questions, The Drive has answers!
Q: How long do tires last?
A: This will greatly vary and depend on driving conditions, driving habits, and type of tire, but the general rule is that tires could last up to 5-6 years. For more information on tire care and maintenance, visit our article, How Long Do Tires Last and When Should I Replace Them?
Q: Is natural rubber used in tires?
A: Yes, though the amount is different for every tire. In general, tires today contain around 20 percent natural rubber and 25 or so percent synthetic rubber. Metal and other materials make up the remaining tire materials list.
Q: What do the numbers on the side of my tire mean?
A: We assume you’re asking about the string of text that starts with “P.” This is a designation of your tire size. If you see P225/65R17 on the side of your tire, it means this:
- P - This means P-Metric, which is a standard used in the U.S. for tire sizes.
- 225 - This is your tire’s width in millimeters.
- 65 - This is your tire’s aspect ratio, which is a comparison of its sidewall height to the width. In this case, the sidewall is 65 percent of the tire’s width.
- R - This stands for radial, which are tires that feature layers running radially across them.
- 17 - This is the size of your car’s wheels. This tire fits 17-inch wheels.
Q: Are cheap tires bad?
A: While cheap tires are not universally bad, there’s a reason high-end tires cost more, and it’s not just branding. Cheap tires may contain less rubber or may be constructed with a mix of materials that don’t give them the longevity of more expensive tire models.
Q: What does the mileage warranty on my tires mean?
A: Your tires’ mileage warranty means that the manufacturer will cover them against defects for the duration of that warranty and that the company expects its tires to last at least as long as the warranty under ideal conditions. This does not mean that only getting 25,000 miles out of a 50,000-mile tire will net you a new set of tires if you complain. It means that, after an inspection, you may be entitled to a new set of tires at a prorated price, which will depend on how many miles you have left on the warranty. If you failed to rotate the tires or take care of them properly, you can expect some pushback when trying to make a warranty claim.
Fun Facts About Tires
You know you want more tire manufacturing facts!
- At some point in the 1960s, Goodyear felt it would be neat to make an illuminated tire, which featured transparent rubber and lighting. The tires were paraded around on vehicles such as the Dodge Polara and Chrysler Silver 300 at the time but never went on sale.
- Tire rubbers are generally white in color and have to be darkened with carbon black.
- Run-flat tires are fairly common, but tire manufacturers have shown off prototype models that don’t use air at all. Michelin offers Tweel tires, which are airless radial tires that replaces the entire wheel/tire setup. They are currently offered for UTVs and some heavy equipment, but the company has developed and shown off automotive prototypes.
- A Michelin engineer told The Drive that his dream tires would be ones that could communicate with a vehicle, which means that a vehicle would be able to adjust its performance to the specific tire it’s wearing at any given time.
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