What 'Brake-By-Wire' Is, and How It Works

Mia Bevacqua
December 10, 2018

Computers and electronics control nearly all systems in cars these days, and the brakes are no exception. These “brake-by-wire” systems allow the vehicle to stop more quickly, with less effort, than traditional brakes.

Let’s look at how traditional and electronic systems work, as well as some common brake-by-wire problems.

How traditional brakes work 

Except for the anti-lock braking (ABS) controls, there aren’t many high-tech electronics in a conventional brake system. Their operation is a simple, hydro-mechanical affair.

The process goes like this: When the driver pushes the brake pedal, it acts on the master cylinder, which in turn forces pressurized brake fluid through a series of lines. Each line goes to a caliper and a set of pads at one of the vehicle’s wheels. When the fluid reaches the caliper, it pinches it shut, forcing the pads against the rotor and bringing the car to a halt.

» LEARN MORE: Find a repair shop near you

How brake-by-wire works

Electronic brake control, otherwise known as brake-by-wire, is different. When the driver applies the brakes, one or more sensors monitor the pedal effort. Typically, acceleration, vehicle speed and steering angle are also analyzed. 

All this data is relayed back to a computer called an electronic control unit (ECU). From there, the ECU applies the brakes in one of two ways, depending on the system design. 

With electro-hydraulic braking, the computer commands a fluid pump and solenoid-operated valves to apply the calipers, bringing the vehicle to a stop.

With electromechanical braking, there are no hydraulics at all. Instead, each wheel has an electronic caliper, which has a motor inside that pushes the pads against the rotor. This design is cutting-edge, and isn’t currently used in production-model cars — though it could be in the future.

Electronic parking brakes can also be considered a brake-by-wire system. Found on many vehicles today, they allow the driver to operate the parking brake with just the push of a button, instead of pulling or stepping on a mechanical lever.

Advantages of brake-by-wire

Both of these designs are more efficient than traditional brakes. Plus, they eliminate the need for a brake booster, a device traditionally used to provide a braking assist.

Brake-by-wire also makes possible new features, such as automatic emergency braking, adaptive cruise control and more.

» LEARN MORE: Get an estimate for your brake repair

Common brake-by-wire problems

Electro-hydraulic brakes can suffer from all the same problems as a traditional braking system. Issues with the brake pads, rotors or hydraulics can lead to symptoms such as noise, or a pedal that’s low or hard.

A problem with the brake-by-wire electronic controls will typically result in illuminated warning lights (ABS, traction control or others), along with improper ABS operation. It may also mean the brakes take braking effort, or give you an abnormal brake pedal feel. 

If you suspect a problem with your brake-by-wire system, it’s best to have it repaired by a professional. 

Mia Bevacqua

About the Author

Mia Bevacqua is an automotive expert with ASE Master, L1, L2 and L3 Advanced Level Specialist certification. With 13-plus years of experience in the field, she applies her skills toward writing, consulting and automotive software engineering.

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