What is a car tire made of and which one is suitable for what?

What is a car tire made of and which one is suitable for what?

They have shaped our streetscape for a hundred years, are a car's only contact with the road and are therefore of immense importance for the driving behavior and safety of vehicles. We are talking about car tires, also known as tyres. The latter comes from the Greek word pneuma, which means air or breath. But what do you actually know about car tires? What does a modern car tire consist of? Who invented these ingenious black “patschers” for cars? What exactly is the difference between summer, winter and the all-season tires that have recently become increasingly popular? And finally: What does e-mobility mean for the tire industry? These questions will be answered in the following article.

In principle, we owe the air-filled tires to two gentlemen who lived and worked in the 19th century. One was Robert William Thomson, a Scottish designer and inventor. For example, the fountain pen and the band saw, but above all the pneumatic tire, are based on him. Thomson was working on a wheel system that would offer more comfort and traction than the carriage wheels with their iron tires that were conventional at the time. On December 10, 1845, he was finally issued British Patent No. 10990 for six months - for the “Aerial Wheel”. The so-called Thomson wheel consisted of a leather tube in which another tube was inserted - this consisted of an airtight canvas fabric vulcanized with rubber and was then filled with air.

This was made possible thanks to another ingenious invention by an American: Charles Goodyear had already received a patent in the USA a year earlier for a process for vulcanizing rubber. Vulcanization is the hardening process through which a car tire gets its shape. Raw rubber is converted into elastic rubber at a certain temperature and pressure.

If you look into the history of tires, you inevitably come across another man whose name is still a household name today and who - similar to Goodyear - is inextricably linked to the tire industry: John Dunlop. Remarkably, the Scot was actually a veterinarian living in Dublin. In his practice he developed apparatus and came across rubber. In 1887 (he was 47 years old at the time), Dunlop finally designed his first air-filled rubber tire.

According to legend, he had a very special motivation for this: he wanted to make his son's tricycle quieter and more competitive for racing against his friends. The Thomson wheel had already been forgotten by then (among other things because it was far too expensive to produce). And so Dunlop had no knowledge of it when he applied for a patent in 1888, the first pneumatic bicycle tire, a very similar invention. The typical bicycle valve is still often called a Dunlop valve today.

So much for the origin story. Of course, useful tire knowledge goes beyond this. So what does a modern car tire consist of? Unlike most bicycle tires, today's car tires are usually tubeless. Looking from the outside in, a car tire can be divided into two main elements: the tread, also known as the tread, and the carcass.

The latter is the supporting substructure, the framework of a tire. It usually consists of two layers, a fabric layer (textile cord insert) made of rubberized rayon (artificial silk) or polyester and an inner layer made of rubber, specifically butyl rubber (which in turn is the short name for isobutene-isoprene rubber, a polymer from the group of synthetic rubbers).

In radial tires (also called radial tires) the fabric also consists of steel cords (this is referred to as steel belt radial tires). Speaking of which: radial tires have long since replaced diagonal tires. The latter were common in passenger cars until the 1960s. They have several diagonally crossed carcass layers. Today, diagonal tires are almost only used in agriculture or on vintage cars. Unbeknownst to many people, the ultimately winning technology of the radial tire goes back to Michelin. The French company registered a patent for it in 1946. Michelin This revolutionized tire construction. Even the first radial tires lasted more than twice as long as diagonal tires.

Back to the carcass: The interior is filled with air and is sealed by the inner layer. This means that the inner layer replaces the tube in modern tubeless tires. The inner layer (also called inner liner) consists of a special rubber layer. It ensures that the air does not diffuse to the outside.

And finally, there is also the tire bead as part of the carcass. The bead forms the inner ring of the tire and ensures the tight connection between the tire and the rim. It consists of three parts: The reinforcement made of nylon or aramid, a strong, heat-resistant synthetic fiber, ensures driving stability and enables precise steering behavior. The core profile is a stabilizing wedge made of synthetic rubber, which fulfills the same tasks as the bead reinforcer and also has a decisive influence on deflection comfort. And finally the core: It consists of steel wire embedded in rubber, which ensures that the tire sits firmly on the rim.

The tread, the second main element of a tire, provides the connection to the road. The tread contains the tread design (tread blocks and grooves) as well as sipes, which are designed differently depending on the summer or winter tires. It is made of natural or synthetic rubber. The treadmill is made up of three parts: the cap (this is the part, the part of the tire that comes into most contact with the road), the base (it is located under the cap, reduces rolling resistance and absorbs shock transmission to the carcass) and the side part (this is located at the outer end of the tread and forms the transition to the sidewall).

The side wall, in turn, represents the external protection of the carcass. It is connected to the tread via the side part and is made of natural rubber. Below the tread there are two more layers: the coil bandages (consist of a nylon cord embedded in rubber) and steel cord belt layers (they give the tire its strength, thereby increasing stability and mileage and reducing rolling resistance). 

As can be seen from all of these statements, modern car tires have a complex structure. This also explains the difference between the products of different manufacturers. Premium quality starts with the raw materials used (from steel to rubber to various chemicals), continues with production and finally ends with quality control.

But what exactly does a tire consist of, i.e. what materials and what proportion? Continental broke this down for its best-selling summer tire as follows:

Rubber (natural and synthetic rubber): 41%
Filling materials (soot, silica, carbon, chalk, etc.): 30%
Reinforcement materials (steel, polyester, rayon, nylon): 15%
Plasticizers (oils and resins): 6%Chemicals for vulcanization (sulfur, zinc oxide, etc.): 6%
Substances that prevent aging and other chemicals: 2%

A tire consists of 41 percent rubber. Not surprisingly, rubber is the most important raw material. Conversely, this also means that more than half of a tire is made of other materials.

By the way, it takes two to three years to develop a new tire until it is ready for the market. On top of that, the industry is faced with the fact that the variety of models and dimensions is exploding. According to internal estimates from a large tire manufacturer, around 80 percent of the market was covered by 153 different tire models in 2005. Today there are already 323 variants and by 2027 there will probably be 524. This makes processes more complicated and timely delivery to customers a challenge. This is also important for professionals to consider and is part of the relevant tire knowledge in 2022.

The rubber mixture is crucial for driving behavior and the right grip on various surfaces. It influences how intense the friction between the tires and the ground is and how good the vehicle's contact with the ground is. Poor grip can increase the braking distance, increasing the risk of an accident. The grip is influenced by the surface, the rubber compound, the correct tire pressure, the tread depth and thus the mileage, but also the age of the tire. “If there is high tire wear, increased fuel consumption can also be expected,” says the website of the tire manufacturer Continental.

Theoretically, there would be a most suitable tire for every driving situation. This is evident in Formula 1, where tires are often changed several times during a race and often in response to changing driving conditions. Of course, this is not practical in everyday life. In Central Europe, however, there is an essential difference that repeats itself every year: that between summer and winter. The rubber compounds of the summer and winter tires are ideally tailored to the respective external conditions.

Summer tires are designed for road conditions without snow and ice. Their rubber compound does not become too soft even at high temperatures and wear is relatively low at high speeds. As the tread depth decreases, the behavior in the rain worsens. The law therefore requires a tread depth of at least 1.6 mm, but car clubs recommend at least 3 mm tread depth for summer tires.

Winter tires (M+S tires) are designed for winter road conditions. They have a rubber mixture that is sufficiently elastic even at low temperatures to achieve sufficient power transmission. Winter tires are marked with the M+S symbol (English for Mud and Snow). Tread pattern, tread compound or structure is primarily designed to achieve better driving and traction properties on snow. Here too, the adhesive properties deteriorate as the tread depth decreases. In Austria, a winter tire must therefore have a tread depth of at least 4 mm, below which the tire is considered a summer tire. 

All-season tires (also known as all-weather tires) can be used in both summer and winter. They represent a compromise between summer and winter tires. They are primarily used in countries where there are small temperature differences between the seasons.  

The profile of all-weather tires combines the two different groove arrangements of summer and winter tires, so that the longitudinal grooves required for higher temperatures and in wet conditions can be found as well as the tread block teeth that provide grip on slippery snow and ice. Especially in the area of ​​all-season tires, which has been a real growth segment for a few years thanks to high demand, the wheat is separated from the chaff. Cheap brands usually perform poorly in relevant tests, but a few well-known manufacturers have been able to make a name for themselves. In addition to brands such as Goodyear and Continental, this also includes the Dutch manufacturer Apollo Vredestein, which has already received numerous awards for its Quatrac all-season tire. 

The properties of all-season tires are naturally a compromise: on snow they do not come close to the properties of good winter tires and in summer they have - because of their inherently softer rubber compound - higher abrasion and therefore wear and slightly increased fuel consumption. According to Harald Kilzer, Managing Director of Apollo Vredestein Austria, all-season tires are justified even in the Alpine republic, but only in niches: “This is in urban areas, for infrequent drivers or even for second and third vehicles,” he says. In addition, the country is too small and the regional differences are too great. “Every Viennese goes skiing at some point. And for that you clearly need a summer and a winter tire,” explains Kilzer.

All-terrain tires should not be confused with or equated with all-season tires. They belong to the off-road tire segment and – as the name suggests – can be used both off-road and on asphalt.

“The right selection depends on individual criteria,” Holger Rehberg, Product Manager Goodyear Dunlop Tires Germany, recently explained to KFZwirtschaft: “These include the kilometers driven annually, the vehicle category and strength as well as individual driving habits.” For vehicle owners who drive less than 10,000 km per year and who primarily travel in urban areas, an all-season tire is sometimes a good alternative, says Rehberg. But if you're traveling across Austria or Germany for work or are driving on a winter vacation, the expert definitely recommends winter tires.
By the way, Goodyear offers a free one online  Tire quiz. Under the motto: "What type of tire are you? With six questions for recommendation", drivers can find out quickly and easily by answering six questions whether they should choose all-season tires or winter tires.

And what should you take into account for electric vehicles? A tire is a tire, the drive doesn't matter? One might think. But that is not the case. Because of the batteries, electric cars are significantly heavier than those with combustion engines and they have a comparatively high amount of torque, which results in immediate, strong acceleration. Of course, both properties result in a higher load on the tires. And then there is the issue of reach, which is of central importance. A lower rolling resistance is beneficial for this.

“We didn't have to reinvent the wheel, but we did rethink many aspects of the tire as we know it to achieve optimal performance,” says German manufacturer Continental. In addition to good grip and low rolling resistance, the rubber mixture used for electric vehicles must also offer maximum robustness. At Conti, the result of relevant research is called EcoContact6, a tire specially designed for electric vehicles.

“Owners of purely electric cars are well advised to use the corresponding types of original equipment when buying new tires,” says Lars Netsch, tire expert at TÜV SÜD. The E-types have advantages, especially in the city and in moderately fast intercity traffic. According to the tire manufacturers, the lower rolling resistance can result in a range that is up to 8 percent longer. 

A lot of research is being carried out in the area of ​​car tires, and not just because of the emerging e-mobility. The tires of the future will become increasingly intelligent (they are connected to the car), more durable and more sustainable (recycling is a big issue). Work is also underway on airless tires. You can see the most exciting future trends  here. 

Speaking of sustainability: Not every defective tire has to be replaced with a new one straight away; sometimes it can be easily repaired. You can do what needs to be taken into account  here  read it and then gain your knowledge all in one  eLearning  check easily and simply. 

Behind all these developments lies an industry with billions in sales. The  largest tire manufacturer in the world  are Michelin and Bridgestone, each of which generates annual sales of around 20 billion euros from car tires. Continental follows in third place. The German supplier giant generated sales of more than ten billion euros in 2020 with its tire division alone.