Still black, but tall, narrow and only discreetly whispering: just as the electric car marks the turning point of mobility in the 21st century, tyres for electric cars are going through a revolutionary change as well.
An increase of 75.5 per cent in 2019 compared to the previous year and the market share almost doubled: the electric car may still be a marginal phenomenon. But the figures show just as clearly that the trend is pointing steeply upwards - not only in the UK, but throughout Europe, the USA and the strong industrial nations of Asia. The shift towards electromobility is in full swing worldwide, and car manufacturers are now chasing range instead of horsepower.
With electric cars, range is synonymous with weight. As a rule of thumb, each additional kilometre increases the weight of modern lithium-ion batteries by about one kilogram. This means that 500 kilometres without a charging stop requires about half a tonne of battery power. Plenty of kilos and one reason why car manufacturers are now working even more closely than before with tyre manufacturers like Michelin in vehicle development. The challenge is, on the one hand, to develop tyres with significantly more load-bearing capacity. This is achieved, among other things, by a specially reinforced chassis. On the other hand, the tyres must also withstand significantly higher acceleration forces: Due to their immediate power delivery, electric cars leave even high-performance sports cars standing at the traffic light. The tyres must therefore bring significantly more torque directly to the asphalt. On the other hand, battery-powered vehicles require much less emergency braking, because as soon as the driver releases the accelerator pedal, the electric motor becomes a generator and "recuperates" - in other words, converts kinetic energy into electricity that is fed back into the battery. The vehicle decelerates automatically. Normal tyres would show significantly higher wear with this requirement profile.
But there is also change in the tyre format: "Tall and narrow is the solution, i.e. narrow yet large-dimensioned tyres that offer lower aerodynamic drag and reduce rolling resistance on top of that. Even in the smallest details, Michelin engineers have found ways to make the tyre more "streamlined": For example, even the tyre sidewalls and side markings are designed with aerodynamics in mind and are not allowed to create additional drag in the wind tunnel.
Michelin was particularly early in the development of tyres for electric vehicles and already introduced the MICHELIN Energy E-V in 2012 for one of the first mass-produced electric vehicles on the market, the Renault ZOE compact saloon. Specially adapted to electric car characteristics, it offers particularly low rolling resistance thanks to its special rubber compound and tread design, which is synonymous with more range. Because the less energy that is wasted in the form of friction on the asphalt, the more kilometres the car can cover.
Beyond pure driving performance, the demands on tyres for electric cars go even further. In addition to rolling resistance, load capacity and dimensions, tyre developers also focus on noise development. After all, the pleasant quietness of the particularly low-noise drive should not be impaired by excessive rolling noise.
Tyre noise is perceived particularly intensively by the driver in an electric car, as the electric vehicles do not have the noise of a combustion engine. Logical consequence: the tyres for electric vehicles must be particularly quietly on the asphalt. That is why Michelin develops technologies in close cooperation with car manufacturers to significantly reduce the noise level. One example is the Michelin "Acoustic" technology: a foam insert in the tyre efficiently "swallows" the vibrations and thus significantly increases the noise comfort inside the vehicle. In addition, the tyre's rolling noise can be further reduced by a special tread design. Michelin's goal is to work together with car manufacturers to implement the future European noise reduction requirements by 2024.