BERLIN: Though they come in many shapes and sizes, EVs (electric vehicles) like the Renault Zoe, the BMW i3 and the Kia Soul, usually have one thing in common: narrow tyres.
The idea behind such "asphalt cutting discs" is that, with a large diameter and narrow tread, the tyres are low-friction and help get the cars as many kilometres as possible with just one battery charge.
"Cars like the i3 are designed for optimum range, and these narrow tyres have a considerably lower rolling and air resistance," explained Volker Blandow from inspecting agency Tuv Sud.
Of course, there are exceptions, with the sporty Tesla S, coming with 245mm width tyres.
"The car has a large battery with enormous acceleration values "of from 0-100kph in under three seconds, but they can only be put on the road with wider tyes," says Blandow.
In the end, whether wide or narrow, the requirements for e-car tyres are quite particular.
"They need a high load capacity to cope with a higher weight as e-cars simply weigh more due to their battery," explains Hans-Juergen Drechsler of Germany's Federal Association of Tyre Trade and Vulcanization (BRV).
In addition, electric cars have higher torque, which is why specially designed, more durable tyres are preferred.
In principle, however, every e-car tyre can also be used for a combustion car and vice versa, according to Drechsler, despite the tailored design.
In the end, the decisive factor is the rubber compound used as it also influences the rolling resistance and, ultimately, the mileage of the tyre.
"Range is a crucial issue for e-cars, so these tyres are energy-efficient and have different driving characteristics than tyres for SUVs or sports coupes," says Klaus Engelhart from tyre manufacturer Continental.
For example, for tyres with particularly good adhesion values, some kind of compromise on rolling resistance must be expected.
In addition, the profile and tyre size also play an important role in energy consumption.
The large diameters of EV tyres - a minimum of at least 19 inches - is also, according to Drechsler, necessary for the braking system to support the extra weight.
In the end, it is a matter of having the right mix for tyre manufacturers.
"A very important component of the tyre compound is the acidic salt Silica, which allows tyres to roll off with less friction," explains Engelhart.
Tyre management is a perpetual a conflict of objectives as a tyre can never be the best in all disciplines at the same time. A compromise is always necessary.
"Driving range is more important in the end than the last bit of ride comfort," says Blandow.
A common misconception is also that a thinner tyre means less control on the road.
However, because EV have the advantage that their drive technology allows for precise power distribution, systems such as electronic stability control work even more efficiently.
Anyone opting for an EV-specific tyre must invest 10 to 20 per cent more, according to the BRV. However, this can pay off quickly, because the optimized low-rolling-resistance tyres also last much longer than normal tyres would on an EV.
"An electric car can get up to 15 per cent more range with optimal tyres, while with petrol car it can be 5 to 10 per cent," says Blandow.
