While disc brakes were largely adopted in modern automobiles for their performance enhancement over drums, today's EVs have two key technologies that allow manufacturers to consider reapplying the simpler drum technology, brake by wire and regenerative braking. The Audi Q4 E-Tron can generate a deceleration of 0.3 g-force, a standard measure for acceleration or decelerations, in its four-wheel-drive variants simply by turning its electric engine into a generator, using the car's forward momentum to recharge the battery, gradually slowing the car without requiring any effort from the braking system. To put that in perspective, that would slow the car from 60 mph to 40 mph in about three seconds. That's far from what would be required in a panic stop, but more than enough to slow when approaching a stop sign or traffic on the highway. Combine that with brake by wire, where the car's computer decides how much to leverage regenerative braking versus physical braking force, and the car can significantly reduce the demands on its braking system as a whole, and especially on the rear axle. A secondary benefit to the drum brakes is their reduced rolling resistance. The pads in a disc brake system can and frequently do ever so slightly brush up against the rotating disc. That's perfect for responsive brake feel, but inefficient for EVs looking to eke out every last mile of range.