Electric driving requires a whisper-quiet tire

Developing a better tire is like trying to cover a table with a sheet. Only the table top gets a little bigger every year. “If you cover the left corner, the right side is exposed,” says technical chief executive Daniele Lorenzetti of Apollo Tyres, owner of the tire brand Apollo Vredestein. “If you slide the sheet to the right, it will be at the expense of the left.”

Better performance is expected from a car tire every year. But if you lower the rolling resistance, and therefore the fuel consumption of a car, you risk losing grip on wet roads. If you make the tire thinner, it may last less. Only by looking for even better materials and technologies can you improve on all these properties, says Lorenzetti. “You want a bigger tablecloth.”

The technical director of Apollo Tires (2.6 billion euros turnover, 19,000 employees) knows all too well that the car tire is a given for many motorists. Once the current set is worn out, they rely on the garage – they don’t ask for a particular brand. But drivers who do understand them know how much difference good tires make. They are the only point of contact with the road, and “a major impact on road holding, safety and comfort,” said Lorenzetti.

So any car tire may be “round and black,” but a contemporary one is “much better than a tire from ten or twenty years ago.” Just as cars are improved every year, the tire industry is constantly looking for a better tire. And Vredestein has quite a few tires to develop: for the passenger car alone, the group already offers hundreds of variations, for different conditions, in different price ranges and specifically for a certain car model.

That evolution is best seen when you cut the tape. Then the reinforcement fibers become visible. Until the 1960s they ran diagonally, nowadays at right angles to the direction of travel. As a result, a tire can absorb vibrations better, wear less quickly and a car steers better. A huge improvement, as has the addition of silica to the rubber compound since the early 1990s, for more grip in the wet and less fuel consumption.

Rubber mixtures

Every new band starts with research. For Vredestein, founded in 1908, this takes place in the product development department in Enschede, where a club of scientists and technicians searches all day long for rubber mixtures that are even better than the existing ones. Lorenzetti calls it “preliminary investigation”. “We don’t want to wait until we start developing the actual tire.”

In one of the rooms, two employees mix the compound, mixtures of, among other things, sulphur, soot, zinc and various types of rubber. On a table are the raw materials for ten recipes that the chemists suspect are promising: powders and slices of rubber, which from a distance resemble fruit jelly and gingerbread.

The raw materials are mixed into pellets in an oven, after which a roller crushes them into one whole. After heating, technicians cut the slab of rubber into samples for the test equipment elsewhere in the building. Divided over trays are round rubber discs in thin slices in the shape of a bow tie and in various sizes.

The relevant properties of each mixture are accurately measured. For example, a device tests the force at which a strip of rubber breaks. There is a machine that determines how high the grip is on different surfaces. A kind of sander measures the wear. Some tests are performed at multiple temperatures or when exposed to ozone, which corrodes rubber.

More or less simultaneously, engineers at a different location are researching the reinforcement of the tyre: the pattern of wires that lie under the rubber like a skeleton. They make extensive use of computer simulations to predict the effect of a particular change. This also happens in combination with a specific compound, because you cannot see the two separately, according to the technical top man. Rubber compound and reinforcement interact with each other.

Only when the new finds are good enough, a tangible bond is made. Then the testing begins, Lorenzetti says, “to validate the predictions you made in simulations.” That happens on machines, and on the road. From idea to marketable product, this process can take two to three years.

dandelion rubber

While tire development was once all about comfort and grip, Lorenzetti sees two other trends that will weigh heavily in the coming years. To start with, sustainability. For fifteen years now, the emphasis in development has been on reducing rolling resistance, and thus the fuel consumption of cars. This property is measured in kilograms of friction per tonne of vehicle weight. “Twenty years ago you could easily exceed ten kilos per ton, now it is six. Especially because tires have become much thinner.”

But durability is more than that: they are also tires that last longer. And tires that consider the reuse of raw materials. Apollo Vredestein wants 40 percent of its products to consist of sustainable materials in eight years’ time. For example, recycled rubber from used tires, but also raw materials of natural origin. The company recently made a prototype bicycle tire from rubber extracted from dandelions instead of oil.

With an electric car you hardly have any sound from the engine. So the band of the future will have to be even quieter

In addition, Vredestein believes that the electric car will need a lot of its brainpower in the coming years. That calls for a different kind of bond, says Lorenzetti. It must be more robust, because electric cars are heavier than fuel cars. In addition, electric vehicles often accelerate faster, which means that more power is applied to a tire in a short time. “The risk is that the life of a tire will be reduced as a result.”

And even more important than with a fuel car is the amount of noise a tire produces. “Because with an electric car you hardly hear any noise from the engine. All sound, all vibration too, comes from the wind and from the tires. So the tire of the future will have to be even quieter.”