The EV Revolution Is Ushering In the Return of Rear-Wheel Drive
As the auto industry designs its next-generation EVs from blank sheets of paper, nearly every automaker has decided that driving the rear axle makes more sense than driving the front.
Electric cars are changing more than meets the eye. As automakers around the globe shift further away from gas and diesel engines, the transition to pure electric drivetrains has questioned conventional automotive design thinking. Why does a passenger car look the way it does? Should the powertrain necessarily be up front? What concessions to design, engineering, and driving dynamics do internal-combustion engines place on a car?
Electric cars present an opportunity to redefine the platforms that vehicles are built on. Until this point, the design and engineering of these architectures have been fundamentally driven by the size of a combustion engine and its various cooling, fuel, air, exhaust, and drivetrain requirements. For decades, the status quo in car design has accepted that the most efficient packaging is a front-mounted engine powering the front wheels (or, optionally, all four wheels). Several of the first mass-market EVs were based on vehicle architectures were designed with these conventional needs as the priority. In EVs like the 2011 Nissan Leaf and 2015 Volkswagen e-Golf, batteries got parked under the rear seat or cargo areas where the fuel tank normally resides, and motors sat under the front hood where a gas or diesel engine would usually be housed.
But that was the old way of doing things. The newest EVs preview a future in which rear-wheel drive will be far more common than it is today.
Automotive Engineers Have Been Freed
With no combustion engine to work around, electric-vehicle engineers have, in many ways, been given a blank slate for unfettered design. Electric motors are significantly smaller than gas engines, with less demanding requirements for cooling and airflow and no need to package long and cumbersome driveshafts or exhaust plumbing. Electric propulsion removes at least seven plumbing, access, and service-related design requirements that must be met for a gas or diesel engine. That means engineers can now place the motor at the back of the car with minimal effect on passenger and cargo space. And that gives them the freedom to choose which wheels drive the car.
Today, many clean-sheet-designed BEVs use a skateboard-like platform where batteries sit beneath the cabin floor powering either a rear-mounted electric motor driving the rear wheels or a dual-motor layout that adds a second motor at the front of the EV for all-wheel-drive capability. That’s exactly what you’ll find in new 2022 EVs like the Ford Mustang Mach-E, Hyundai Ioniq 5, Kia EV6, and Volkswagen ID.4. These examples are compact and mid-size utility vehicles that, if they were powered by gas engines, would be built around a front-/all-wheel drive architecture. So why would engineers be motivated to make the switch?
Rear-Wheel Drive Distributes the Work
A front-wheel-drive car, whether it’s powered by gas or electricity, asks a great deal of its front tires. They have to accelerate the vehicle, they have to steer, and in conjunction with the rear, tires, they bring the vehicle to a stop. When you ask the tires to do two of these things simultaneously, they’re more likely to lose grip and start to slip. If the front tires are asked to change the vehicle’s direction with 100 percent of the available traction, there’s no grip leftover to accelerate or slow the car. And if the car is accelerating, it takes grip away from the front wheels at the exact moment that grip is at a premium.
Electric motors make their peak torque nearly instantly. In a front-drive EV like the Chevrolet Bolt, this makes it easy to accidentally spin the tires by prodding the accelerator too hard, particularly when accelerating while turning. Separating the steering axle from the drive axle with a rear-mounted motor alleviates this problem.
Rear-wheel drive, however, has traditionally been associated with problematic handling in slippery conditions such as snow-covered roads. In these situations, a rear-drive vehicle is more likely to fishtail or slide if the driver accelerates too hard. Will that be a problem for rear-wheel drive EVs?
Likely not. The weight carried by a tire has a direct effect on how much grip it offers, and there’s a big difference in weight distribution between a gas and electric rear-drive vehicle. With a front-mounted engine, most gas vehicles carry the majority of their weight on the front axle. EVs, with their heavy, centrally located battery packs do a better job splitting that load, sometimes carrying more weight on the rear axle than on the front.
In the event that the tires start to slip or the vehicle begins to slide, engineers will program stability control and traction control systems to keep the vehicle under control. And many models will offer all-wheel drive for those drivers in Snowbelt states who have come to depend on it.
No longer constrained by the requirements of a combustion engine, carmakers can focus on what dynamically makes the most sense with EVs. With the flexibility afforded by modern EVs, chassis engineers can design the platform in a way that makes the vehicle the most stable, most balanced, most natural-feeling car to drive under all circumstances, with mechanical duties reassigned to where they are best served.
Redefining the Automotive Interior Space
With the smaller footprint of electric motors and the freedom from a compromise struck for decades with front-wheel-drive combustion powertrains, packaging an electric motor between the rear wheels is far easier. The newfound space between the front wheels can allow for an available front trunk, or “frunk”, to increase practicality even further.
Even more fundamentally, without a conventional engine up front or driveshaft sending power to the rear wheels, an electric car designer can shift the front of the cabin forward, creating a larger space for passengers and cargo. A vehicle like the new VW ID.4 can claim to offer the interior space of a mid-size vehicle while casting the shadow of a smaller car. And by having more freedom to choose the drive wheels without conceding to limitations due to a combustion powertrain, automakers can build a car, quite literally, more in harmony with itself.