When it comes to making a car slow down, for the last few decades pretty much every car on the road has used the same idea: a brake disc mounted to the axle with calipers that press high-friction pads onto the disc's surface, slowing its rotation. It's a tried-and-tested formula, one that car makers adopted from the aerospace industry as a better solution than the venerable drum brake. But the boffins at Continental (the tire company) have been rethinking the standard way of doing things, specifically in the context of small and medium-size electric vehicles. Enter the New Wheel Concept.

The focus on EVs is logical, since, in their case, deceleration is often achieved via regenerative braking using the electric motor instead—at least on the driven wheels. Obviously, EVs can't ditch the conventional brake. There needs to be a redundant system for situations when regenerative braking isn't possible, like when the battery is full and can't accept more energy. A consequence of using regenerative braking is that the friction brakes get much less use than in a conventional car, so they tend to last a lot longer. But there is a downside to this: a buildup of rust that can impair their performance when you need to use them, according to Continental. (This is only an issue with cast iron brakes, but we're not aware of many hybrids that use carbon ceramic discs outside of the hypercar crowd.)

"In EVs, it's crucial that the driver expends as little energy as possible on the friction brake," said Paul Linhoff, head of brake pre-development in the chassis & safety business unit at Continental. "During a deceleration, the momentum of the vehicle is converted into electricity in the generator to increase the vehicle’s range. That's why the driver continues to operate the brake pedal—but it certainly doesn't mean that the wheel brakes are active, too."

So there's a wheel rim, to which the tire is mounted, and then an inner component called a carrier star—the bit with spokes that mounts to the axle. Instead of mounting a brake disk to the axle, here it's married to the carrier star, with the caliper attached to the inside. That means that the disc can be much larger than a conventional brake disc, which needs to be small enough so that there's room to fit the caliper without impeding the wheel itself.

It's also made of aluminum rather than cast iron, solving that rust problem. But Continental says there are some other advantages, too. For one thing, aluminum is lighter than cast iron, and any weight you can save from an EV loaded down with batteries is a good thing. (We believe the weight savings to be about 4.4lbs/2kg per wheel.) Second, aluminum is a good conductor of heat that's more quickly dissipated than with a conventional set up. And finally, the larger brake disc means a better leverage effect from the caliper, which in turn means a smaller caliper is possible.

"Because the brake disk is fixed on the outside and the brake engages from the inside, the brake caliper can be designed particularly light and stiff. The force is transmitted largely symmetrically into the center of the axle, and this has a favorable effect on the noise behavior of the brake," Linhoff said. Again, that's not something you'd care about in a car powered by a noisy internal combustion engine, but it is another plus when it comes to the silent driving experience that EVs offer.