Electric and penumatic cars, because you need something special

The electric cars need special tires . Because? Essentially for the greater shooting acceleration which puts the tires under strain immediately and also for the different weights at stake. But there is also something else. Here's how one specialist absolute as Pirelli tackles the problem

The tire design is an action of perfect scientific balance. The goal of the designers is to create a product that has an excellent seal, which lasts forever and is extraordinarily silent; however, they have to face a challenging compromise because the characteristics of the rubber are often at odds with each other. A tire with good handling will wear out quickly, a tire that lasts a long time is noisy, while a flexible and silent tire could make the driving experience difficult.

With the advent of the electric car, the work of the designer is further complicated and the engineers at Pirelli devote themselves to the development of products able to meet the needs of different car manufacturers. The considerable torque of electric cars puts heavy demands on the tires, which must be resistant, have an excellent seal, but not too much, not to run out of battery power, of vital importance. At the same time, the silent engine increases the perception of the noise of the tires, and being able to reduce it is therefore essential.

It is about reaching the right balance . Reduce rolling resistance and noise, while increasing manageability and safety “. Explains Filippo Bettini Pirelli's Chief Officer of Sustainability and Risk Governance. “ It is possible to produce a tire with a low rolling resistance. But the estate on the ground will necessarily be lower. With the consequence that it may not be safe . “

It is a complex task which implies an immense work undergoing design . Researchers experience an impressive series of variables modify the composition of the rubber compounds construction techniques, the placement of the belts, the lateral structure, the tread, width and depth of the grooves. All with the ultimate goal of finding the best mix of features for each model.

Torque: immediate power

Regarding the specific needs of electric vehicles with regard to tires, the most important is the ability to resist a huge torque . That is the rotating force that makes the wheels move . This is due to the fundamental differences between the way in which traditional internal combustion engines and electric ones generate and use power.

Internal combustion engines generate heat by combining air and fuel inside a chamber , burn the mixture to produce a high pressure gas that expands and moves the pistons; this upward and downward movement is then transformed into rotary motion by means of a drive shaft. To be able to move, the stopped engine must draw in air and fuel, therefore immediate start is not possible. In addition, the mixture of air and fuel takes time, and this limits acceleration.

Otherwise, the electric motor, essentially a very modern magnet, does nothing more than withdraw the stored electrical energy and transform it into a pair. By simply pressing a button. No complex chemical process, no delay. The result is that sudden and surprising acceleration, and extraordinarily silent, that requires resistant tires with a very good grip, able to transfer the power to the ground and keep the car under control.

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Traveling comfortably

There is then the need for to maximize the distance traveled between one charge and the other. The more kilometers you travel with a volt, the better, especially in the case of long journeys that require the need to recharge the battery. The result is the r rolling existence of the tires, which refers to the tendency of the tire to deform. The greater the change in the shape of the tire, the more energy will be used to keep the car moving.

The most obvious solution is to create a very hard tire with resistance very low rolling. There is however a compromise to keep in mind. That is, the fact that the car can travel a longer route between charges, but the journey will be much less comfortable. For example, a tire in metal has almost no no resistance to rolling. But it would be able to transform even the most luxurious electric car in the world into a very uncomfortable and clanking transport

For this reason the goal is to achieve a balance that is suitable both for the car and its use. The driver of a compact electric car that drives a lot in the city will probably be happy to compromise maneuverability and grip to achieve greater versatility and efficiency. The owner of a Tesla could instead prefer one emphasis greater on better handling. And the possibility of crushing the accelerator safely for a real adrenaline rush.

Strong and Silent

As electric cars are silent, and tire noise amplifies, acoustics is a vital factor in designing them. Especially in terms of tread size of the block and width and depth of the groove . Once again it is the type of car that influences the spirit of the manufacturer. If you are producing a tire for a small electric car for urban use, which travels slowly and generates little noise, acoustics will not be a problem. If you are producing a tire for a heavy and high power model, noise reduction is one of the priorities.

Then you have to think about the weight . Electric cars have heavy batteries and an unusual vertical weight distribution. This generates voltage during acceleration and steering. With the consequence that the tire structure must be extremely resilient . To ensure prolonged use and a suitable service life, these tires can not be cheap . It is necessary to reinforce the whole carcass, using the measures, number and position of the new steel internal belts.

Producing the perfect tire for the new fleet of electric cars is really complex , and fascinating. And the challenge requires a rigorous science, an innovative thinking, as well as several thousand kilometers on the test track. The race has already begun and the reward for the winner will be immense.

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