How rear-wheel drive became an EV 'must-have'

Earlier this year Volvo Cars announced it would end a self-imposed, safety-related boycott and produce rear-wheel-drive cars for the first time in a quarter century.

Not long after that, sibling brand Polestar said the power in the car's single-motor variants would for the first time switch to rwd from front-wheel drive.

With the shift, Volvo and Polestar joined Tesla, Volkswagen, Hyundai and Kia in favoring rwd for base models for reasons that include better performance and improved efficiency.

For example, the power in the new Polestar 2 rwd variants with a single electric motor increases to a high of 220 kW (295 hp) from 170 kW (228 hp) while torque rises to 360 pound-feet from 243 pound-feet compared with the fwd models.

The revisions reduce the midsize fastback's 0 to 62 mph acceleration time by 1.2 seconds to 6.2 seconds, Polestar said, adding that wasn't the only advantage.

"When we reduce the weight on the front axle, we make the car a little bit more agile and a little bit more fun to drive,” Polestar Head of Chassis Development Joakim Rydholm told Automotive News Europe. "So, we improve traction, we improve directness, speed of response, and that together gives more driving pleasure. This means we can improve comfort without sacrificing on performance and the handling."

Volvo stopped making rwd cars in 1998 because it believed fwd models were safer to operate because they typically perform better on snow and ice, even if it meant forgoing some of the handling and maneuverability advantages offered by rwd models.

Polestar's head of product attributes, Christian Samson, told ANE that weight distribution in the past was a trouble spot for rwd cars.

"In the old days one disadvantage of having a light rear end was that rear-wheel drive would be 'exciting' in some moments because of a loss of traction," he said.

Improvements to traction control systems combined with the battery pack's location help distribute the car's weight more evenly over the drive wheels resulting in better grip on the road, especially in wet or slippery conditions.

Another key advantage to rwd is that the configuration gives engineers more leeway when packaging the propulsion systems because the rear-mounted electric motor takes up a minimal amount of room, leaving more space for passengers and luggage.

Better driving dynamics

Volkswagen's head of engine development, Karsten Bennewitz, told ANE the company's electric car family is primarily rear driven, adding that future VW EVs will either be rwd or all-wheel drive.

"We can create some advantages in the overall driving dynamics of the car by installing the rear-wheel drive as a main propulsion system," he said. "Second, by doing so, we can create a very small turning radius for the whole car relative to its size."

Bennewitz added that improved traction and acceleration are additional benefits, noting the overall fun-to-drive factor will be important in persuading customers to join the push to EVs.

"We are convinced that electric vehicles are the only way to solve the emission problem in Europe and worldwide, and to convince a customer, you need a carbon-neutral concept that is fun to drive," he said. "We must convince customers that in their daily usage an EV can create the maximum torque within milliseconds from the standstill."

Instant torque availability

Hyundai's first from-the-ground-up electric car, the Ioniq 5, is built on the company's Electric Global Modular Platform (E-GMP). It is offered in rwd and awd variants, while the new Ioniq 6 will be offered in three variants -- one rwd and two awd.

David Labrosse, head of product planning at Hyundai Europe's technical center, told ANE that buyers of the awd variant can deactivate fwd, effectively turning the car into a rwd vehicle.

"When you are on the highway driving 90 or 100 kph, you can do this without front axle, and there we have a unique technology that mechanically disconnects the front motor," he said. "This enables us not to have any braking effect on the front axle, and now you have an efficient rear-wheel-drive vehicle."

Labrosse also touted the instant torque availability and more balanced weight distribution as key advantages of rwd.

"Electric motors provide near-instant torque, which enables us to have amazing acceleration," he said. "When you have a lot of power, a lot of torque, it make more sense to use rear-wheel drive because when you accelerate, the nose lifts and you have more pressure or more weight on the rear axle, which enables you to transmit more torque and, therefore, accelerate."

Since electric motors are usually compact in size, vehicle designers have more options for cabin configuration, In addition, placing the drivetrain at the rear of the vehicle allows for a "cab-forward" concept.

"This allows you to design in much more cabin space," Labrosse said. "Generally speaking, dedicated electrical platforms, with some further innovations, will enable greater space."

Bennewitz said Volkswagen will continue to develop its rwd and awd strategy as the company continues its EV evolution.

"We are intensively developing new concepts right now," he said. "Power identity will increase because the development of the electromagnetic circuits is still ongoing, improving with every generation."

He added that when he looks out across the competition he sees an increasing number of EVs with rwd, likely due to performance, traction and stability benefits.

"We see a general trend to rear-wheel drive in the market," he said.

Rydholm acknowledged that competition within the EV space is growing more intense. One reason Polestar switched to rwd from fwd is because it sees the move as a way to get to the next level.

"I can't speak for the others,” he said, "but for us it was a natural step."

Douglas A. Bolduc contributed