- Mercedes has developed a new in-drive braking system touted as having several significant advantages.
- It is "virtually maintenance-free," traps brake dust, is better for the environment and promises to eliminate brake fade.
- The system is currently being tested with no clear time frame for a production application.
The vast majority of cars have outboard brakes that are connected to their wheel hubs, and only a handful come with inboard brakes. Mercedes has taken things one step further and put the brakes inside the housing of an electric vehicle’s drive unit, and it’s touting multiple advantages, including never having to service the brakes for the lifetime of the car.
Electric vehicles can use their motors to slow down, not only saving their friction brakes from wear but also putting electricity into their battery pack. Various companies have proposed different types of brakes for EVs, from Continental’s ultra-thick mountain bike-like disks to the drum brakes that Volkswagen equips all vehicles built on its MEB platform, like the ID.4 or Audi Q4 E-Tron.
VW argues that even in its EVs with over 300 horsepower, drum brakes are sufficient for the rear. Most of the braking is done by the front brakes anyway, so going back to this older style of brakes (which is cheaper than disk brakes) is one way VW has adapted its vehicles for electric propulsion.
Mercedes has now taken this one step further with its in-drive brakes. However, it hasn’t simply taken a traditional disk or drum brake setup and put it inside the drive unit. It completely reimagined braking, and in the version of the system they showed us in Stuttgart last week, the disk is water-cooled and it doesn’t spin, and the brake pad is circular and it spins with the motor.
There is no traditional caliper either and scrubbing speed is achieved by pushing the circular brake pad onto the stationary disk. Mercedes says this system shouldn’t require service for the lifetime of the vehicle and all the brake dust it generates is kept inside the system in a compartment that doesn’t need to be emptied.
The upcoming Euro 7 (EU7) emissions standard doesn’t just look at tailpipe emissions. It also takes tire and brake particulate emissions from vehicles into account, so keeping brake dust from going into the environment will become more of a talking point in Europe once EU7 comes into force in 2026.
This seems like a big departure even from the inboard brakes that we already know. Mercedes argues there are plenty of advantages aside from the system being “virtually maintenance-free.” Since the disk is water-cooled, brake fade under heavy use shouldn’t be an issue. It also reduces unsprung weight, which improves handling.
Another advantage touted by the manufacturer is being able to equip vehicles with completely covered, aerodynamic wheels that will help lower vehicles’ drag coefficient. The system would also reduce braking noise, and owners wouldn’t be met with rust-covered brake disks after not driving their cars for a few days.
We didn’t think this was such a big issue, but Mercedes told us this specifically was something it got many complaints about. The Mercedes engineer who explained how this new braking system works said removing the caliper from the wheel will give designers even more freedom to create unique-looking wheels, but it will be hard to convince car enthusiasts that this is an advantage.
