What is an electronic brake force distribution system

How Electronic Brake Force Distribution Works

Electronic Brake Force Distribution (EBD) enhances safety by optimizing the distribution of braking force among a vehicle’s wheels. It works in conjunction with other systems, such as Anti-lock Braking System (ABS) and Electronic Stability Control (ESC), to ensure maximum braking efficiency and stability, especially in challenging driving conditions. This article delves into how Electronic Brake Force Distribution works, its importance in vehicle safety, and the technology behind its operation.

Electronic brake force distribution is designed to apply the correct amount of braking force to each wheel to stop the vehicle during hard braking and emergency braking situations while maintaining stability control.

The Basics of Electronic Braking Force Distribution

When a vehicle brakes, the weight shifts forward, increasing the load on the front wheels while reducing it on the rear wheels. This weight transfer means that the front brakes must handle more braking force to stop the vehicle effectively, while the rear brakes require less force. If too much braking force is applied to the rear wheels, they can lock up, leading to skidding and loss of control. Conversely, insufficient braking force on the front wheels can reduce the overall stopping power of the vehicle.

Traditionally, vehicles used mechanical proportioning valves to regulate the amount of braking force sent to the rear wheels, reducing it as the load decreased. However, these systems were not adaptable to varying conditions, such as changes in load, road surface, or vehicle dynamics, and could not provide optimal braking performance in all scenarios. This is where Electronic Brake Force Distribution comes into play.

On older vehicles the front brakes perform about 70% to 80% of the braking power. That’s because the front weighs more than the rear (engine, transmission, driver, passengers, etc) and during hard stops vehicle weight transfers forward. Forward weight transfer causes nose dive which shifts even more weight onto the front brakes. The rear brakes simply prevented rear-end lift and aided in stability.

Mechanical proportioning valves reduced rear-end lift

Older vehicles also used a variable proportioning valve located in the rear of the vehicle. The valve was mounted on the rear axle, with a sensing rod connected to the body. During hard stops, as body weight shifted forward causing nose dive, the rear of the vehicle would rise. The sensing rod detected this rear end lift and moved a mechanical valve that diverted more brake fluid pressure to the rear brakes. The added pressure neutralized rear end lift and weigh transfer.

Automatic emergency braking (AEB) and stability control changed things

Late-model vehicles still carry more weight in the front of the vehicle. But they now have automatic emergency braking that’s designed to apply the brakes hard enough and rapidly enough to prevent a crash.

During an AEB event the hard braking and forward weight transfer can overwhelm to front brakes, causing the tires to lose traction, even with ABS assistance.

The most sensible way to reduce weight transfer and nose dive is to apply more rear braking power and apply it sooner in the process.

EBD senses hard braking and immediately distributes more braking power to the rear wheels to prevent rear-end lift, forward weight transfer, and nose dive. The result is more even braking from front to rear and faster stopping.

How EBD works

EBD uses the same wheel speed sensors as the ABS system. It also uses sensors to detect rapid deceleration and body weight shifts. To redistribute the braking force, the system uses Brake Force Modulators built into the ABS valve unit.

Continental MK C1 redundant brake system

How EBD affects brake pad wear

In older vehicles where the front brakes performed 70% to 80% of the braking, it was normal for the front brakes to wear out twice as fast as the rear brakes. With EBD, shops are seeing equal wear front to rear and in some cases, more rapid rear brake pad wear. How fast the rear pads wear is directly related to how hard the driver brakes.

©, 2023 Rick Muscoplat