Under the skin: How tyres are changing for electric cars

Continental Conti silent

ContiSilent foam layer is claimed to cut noise by 9dBA

EVs require substantially different tyre technology, so Continental, Hankook and Michelin have responded

Are EV tyres all that different from what went before? Or will any old tyre do? 

A lot of drivers will just want the cheapest deal, despite all the evidence that in terms of grip, handling, braking distance, comfort, noise, economy, performance in the wet and wear rate, a premium tyre will outperform those from super-cheap unknown brands. 

But fitting a tyre to an EV that isn’t designed for the job could turn out to be a costly mistake. So why is engineering tyres for EVs a different proposition from designing tyres for an ICE car? There are four reasons.

First, EVs weigh a lot more, because of battery weight. For example, the entry-level Volkswagen ID 3 weighs almost 30% more than the conventional Volkswagen Golf equivalent.

Then there’s torque. With an electric drive motor, high torque is transmitted to the road instantaneously. Even on fairly ordinary EVs, torque can be brutal and that can potentially lead to increased wear.

Noise is a major factor, too. Since the drivetrain of an EV is so quiet even when accelerating or cruising at motorway speeds, road and wind noise become much more obvious.

Finally, there’s economy and rolling resistance. While it’s true rolling resistance affects ICE cars as well as EVs, a 10% increase in rolling resistance over a 200-mile drive is likely to be more noticeable to the EV driver than the ICE driver.

Tyre manufacturers have dealt with the extra weight by increasing the load-bearing ability of the carcass and specifically by beefing up the sidewall construction and using tougher rubber materials.

In 2021, Continental claimed to have manufactured the first tyre with a load rating of HL (‘High Load’, with a load index of 825kg), while an ICE car of the same size might have a rating of SL (a load index of 94kg).

Continental also developed a new compound for its EcoContact 6 called Green Chili 2.0, which consumes less energy when deformed (as it rolls) and reduces energy consumption by 15% compared with its predecessor, and other tyre manufacturers have developed lower-rolling-resistance compounds too.

The design of the tread, how it’s distributed on the road surface, the design of the internal belts and even the bead that grips the wheel rim all have an effect on rolling resistance, which is something for engineers to think about when developing tyres for heavier, torquey EVs.

Tread block widths are already varied randomly to keep droning noise to a minimum, and their design is under even more scrutiny now. Foam layers on the inside of the tread help soak up noise from vibration, too. Continental calls its polyurethane foam layer ContiSilent, which it says cuts road noise by 9dBA.

Michelin’s equivalent is called Michelin Acoustic, and Hankook has come up with another novel idea in addition to foam in the form of a knurled pattern in the base of the tyres grooves.

Source: Autocar

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