Demystifying F1 cars' brake-by-wire systems

Brake-by-wire is a complex system with an innocent sounding name that many people have asked me about, so this month I will explain what it is and why it’s important in a Formula 1 car. 

We should start by understanding the phenomenal ability of a Formula 1 car brake system. Cars today can reach up to 5G on braking – that’s around five times what a road car can reach under the most extreme braking manoeuvre. This means that a huge amount of energy is expended by the brakes.

In F1, we would regard a heavy braking event as one that might dissipate over 2000kW of power over a period of at least one and a half seconds. When you consider that the maximum power from the engine and hybrid system combined is around 680kW, and this power can give phenomenal acceleration, you start to grasp how special the brakes on an F1 car are. 

We also need to understand that the hybrid system recovers energy as well as helping power the car, and this recovery occurs under braking. Currently, the hybrid system can recover energy at a rate of 120kW. Next year this will increase to 350kW, which represents 17.5% of the braking power of the car.

We must not confuse power and energy. If we multiply the power that’s being absorbed by the time that it’s being absorbed, we get the energy that is recovered. In the case of a 350kW system, braking for one and a half seconds we will recover just over half a megajoule. This energy is used to charge the battery where it is stored, ready to be deployed to help accelerate the car. 

So far so good. The electrical energy recovery system is harvesting the brake energy, which otherwise would have been turned to heat and wasted, and in so doing is both increasing the overall efficiency of the vehicle and giving the brakes an easier time. But what happens if the battery is fully charged and can’t absorb any more energy?

In this case, the control system will stop the recharging as it’s not safe for the battery to be overcharged. Now, considering the energy recovery system only works on the rear axle, this would not just drastically affect the stopping power, but also the brake balance between front and rear. In a race car operating at the limit this could be catastrophic.

Heavy braking in a Formula 1 car might dissipate over 2000kW of power over a period of at least one and a half seconds

Photo by: Andrea Diodato - NurPhoto - Getty Images

This is where the brake-by-wire system comes in. The braking system hydraulics still operate the front and rear callipers. The fronts are operated directly with pressure applied from the master cylinder, but the rears pass through a hydraulic valve system that controls the pressure in the rear brake line somewhat independently of the pressure applied by the driver via the rear master cylinder.

The rear brake line pressure is monitored along with the state of charge of the battery, and the brake-by-wire system then arbitrates how much of the rear axle braking torque can be handled by the energy recovery system and how much by the callipers. If the battery is capable of taking charge, the control system will allow full electrical braking capability and then ‘top up’ the required full braking by applying a specific pressure to the rear callipers.

This may well change during the braking manoeuvre and the system must allow for this, constantly sampling the driver demand by measuring the brake line pressure upstream of the brake-by-wire manifold as well as the state of charge of the battery. It then uses the car’s normal hydraulic system to apply pressure, via a servo valve that proportions the pressure, to a mechanical valve that provides pressure to the rear brake line.

Since the brakes are a critical safety system, it must be fail-safe. This is achieved by providing a direct connection via the mechanical valve from the master cylinder to the rear brake line

Two further aspects are worth mentioning. First, since the brakes are a critical safety system, it must be fail-safe. This is achieved by providing a direct connection via the mechanical valve from the master cylinder to the rear brake line. If the hydraulic system were to fail, this allows rear brake pressure to be applied directly. It may not provide the best braking, but would allow the car to slow down in a controlled manner.

The second feature that the brake-by-wire system allows is for the ‘shaping’ of the rear brake pressure to be controlled. Drivers use a different balance of front and rear brake pressure for different conditions, even different corners. The system allows this to be easily altered and can even shape brake pressure distribution through the braking event, which maximises braking performance and also allows the system to help the car balance.

The system is complex, but hybrids could not function safely without it, and the benefit of tuning the brake balance easily provides a positive advantage.

This article is one of many in the monthly Autosport magazine. For more premium content, take a look at the September 2025 issue and subscribe today.

Drivers can change the balance of front and rear brake pressure for different conditions and even different corners

Photo by: Zak Mauger / Motorsport Images