The shape of the electric motor and, more importantly, the electric cars that those powers may change. On CES 2025electric motor manufacturer Donut Lab has unveiled its second generation of wheel drive units. The new engines promise big power and torque with very little weight and, like the company's namesake, a big hole in the middle.
The way EVs are designed inherits much of the architecture of combustion cars: there is an engine (sometimes two or three) somewhere in the body of the vehicle that is connected to the wheels via a drive train. Electric in-wheel motors promise to collect and move those components into the wheel arches, freeing up cabin space for people and cargo. However, there is one big problem that Donut thinks it can overcome: the motors are very big and very heavy.
Donut Lab's second-generation donut motor squeezes into a 21-inch rim, promising up to 630 kilowatts (845 horsepower) and 4,3000 newton meters (3,171 pound-feet of torque) per unit. Before you get too excited about that torque number, consider that “normal” electric motor torque is usually measured at the rotor before it's multiplied by a single-speed gearbox that donuts don't have. So while the 21-incher's hard torque output is certainly impressive, it's not exactly a quantum leap over, say, a Tesla powertrain.
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Where the donut-shaped engine shines, however, is its weight — every EV engineer and designer's nemesis. The 21-inch unit is said to weigh just 40kg, or about a third of a traditional rotor-stator electric drive. Less weight means more range. Of course, you need two motors per “axle” (unless you're building a trick), but with the added weight savings of ditching the half-shafts, CV joints and other drivetrain components, Donut reckons its countless wheels can save hundreds pounds. Lighter weight means more range, which is good. Alternatively, more motors for the same or less weight means more precise control and more overall power, which is really good!
The engine maker also claims its engines are up to 50% cheaper to manufacture, saving around 120 parts along the way. That could make for cheaper cars down the road. Moving the engine into the wheel arches also saves space in the chassis that can be repurposed for cargo, passengers, more batteries or experimental aerodynamics. (Think of Jaguar i-Pace or Polestar 3the front wings of, but even wilder.)
The Donut design integrates the motor and its cooling hardware into the rim of the wheel, saving weight and freeing up chassis space.
Of course, the elephant in the room is that while the Donut Lab's wheels are lighter than previous wheel motors, they're still heavier than conventionally powered wheels. More importantly, they add weight in the worst place a car can gain weight: under the suspension. As is known, unsprung mass gain has a much greater impact on performance and comfort than comparable mass gained in the chassis, and the vehicle's rotating mass is even harder to argue. With more than 80 extra spokes per wheel, there's bound to be some impact on braking, handling and ride quality, though how much remains to be seen.
In addition to the 21-inch car wheel, Donut Lab also showed off the efficiency-focused semi-truck version of the 21-inch wheel, which boasts a lower operating rpm of 200 kW and 2,212 lb-ft (3,000 Nm) per wheel. The lineup will also include a 12-inch scooter motor (15 kW) and a 120 mm drone motor (3 kW). Donut's 150kW 17-inch motorcycle is already on the road for a few boutique electric bikesso the chances of seeing this technology on a car in the future are better than you think.