Mercedes' new brakes to improve EV performance, reduce brake dust

Feb 24, 2025

The system replaces calipers with a circular brake pad on the motor’s output shaft, pressing against a water-cooled ring.

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Jijo Malayil

There is no traditional caliper; instead, scrubbing speed is generated by pressing the circular brake pad against the stationary disk.

iStock

German carmaker Mercedes Benz has proposed a more efficient braking system for electric vehicles (EVs).The concept, called ‘In-Drive Brakes’, relocates the braking system from the wheels to the electric drive motor. Positioned where the half-shafts connect, the innovative design integrates the brakes directly into the motor assembly.The Mercedes system replaces calipers with a circular brake pad mounted on the electric motor’s output shaft. The pad presses against a stationary, water-cooled ring within a sealed enclosure.While the prototype demonstrates this approach on the rear axle, it has the potential to function on both the front and rear axles.According to Mercedes, the innovation offers better ride quality, cleaner streets by containing brake dust, and streamlined wheel designs for improved aerodynamics.

EVs rely on regenerative braking for 98 percent of their deceleration needs, but friction brakes are still essential for the remaining 2 percent, especially during critical high-demand stops.A complete emergency stop may need up to 2200 kW of power, but regenerative braking usually provides up to 290 kW. However, because friction brakes are rarely used, their rotors typically rust, which results in brake dust, noise, and decreased efficiency.

Mercedes is creating an inventive remedy known as In-Drive Brakes to address these problems. This concept relocates the brakes from the wheels to inside the electric drive motor, near the half-shafts connecting to the wheels. Currently demonstrated on the rear axle, the system could potentially work on both axles.In contrast to traditional disc brakes, the In-Drive Brakes function similarly to a clutch system in manual gearboxes. For EVs, a cleaner, more integrated, and more effective braking solution is provided by a rotating disc that is fixed to the half-shaft.

The proposed braking system replaces conventional disc brakes with a design resembling a manual transmission clutch. It features a rotating disc, integrated with the half-shaft of each wheel, coated with friction material near its edges.

Two fixed, non-rotating flywheel-like plates flank this disc, with an annular hydraulic cylinder compressing the assembly. This causes the friction disc to drag against the fixed plates, slowing the vehicle.To disperse heat produced during braking, the system has liquid-cooled fixed plates that are completely contained in housings at the motor’s ends. Each brake housing incorporates a sump to collect brake dust, ensuring brakes that endure the car’s lifespan.

According to Mercedes, by removing the requirement for cooling air passages, this enclosed design guarantees silent operation maintains clean wheels, lowers unsprung weight, and provides design flexibility for wheels.

The idea works well with front-motor configurations or even cars without motors, which makes it more appealing for EVs if the price is comparable to that of conventional brakes. The system complements the cutting-edge technology of the Mercedes Future Technology Lab and is quiet, effective, and low-maintenance. We’re excited to see this innovative method used in the next car models since it has the potential to revolutionize braking systems completely.Mercedes claims the In-Drive Brake system is designed to last the vehicle’s lifetime without requiring servicing, potentially saving owners thousands in brake repairs and replacements. Brake dust is collected in a sealed compartment that never needs emptying.

Jijo Malayil Jijo is an automotive and business journalist based in India. Armed with a BA in History (Honors) from St. Stephen's College, Delhi University, and a PG diploma in Journalism from the Indian Institute of Mass Communication, Delhi, he has worked for news agencies, national newspapers, and automotive magazines. In his spare time, he likes to go off-roading, engage in political discourse, travel, and teach languages.

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