Brake-by-wire, F1-style

How does an F1 car’ braking systems work? The brake-by-wire system is complex and has been reinvented with the hybrid era

BY CHRIS THOMPSON

WHEN YOU THINK ABOUT the abilities of a Formula 1 car, its acceleration and downforce are usually what come to mind. But in the last few years the braking systems in F1 have become arguably just as impressive.

Before we dive into how they work, let’ look at the basics of braking and how the previous conventional system worked. Much like the brakes in the vast majority of road cars, the system used pre-2014 in F1 cars had direct physical connection from the pedal to the caliper.

To simplify it somewhat, pressure from the pedal transfers through the master cylinder and pressurises the fluid in the brake lines, which acts on the calipers. The calipers then, as we all know, clamp and apply friction to the disks, slowing the car. Rather dramatically, in the case of F1.

“BRAKE-BY-WIRE ALLOWS A GREATER LEVEL OF CONTROL OVER BRAKING PRESSURE FOR MORE BALANCE AND STABILITY”

In 2009, the Kinetic Energy Recovery System (KERS) was introduced to F1, and this changed the braking game somewhat. As KERS harvests power under braking, it also creates friction and results in more dramatic deceleration. In 2009 this wasn’ a huge issue for drivers, as KERS was limited to harvest a maximum of just under 60kW. Until 2014, rear brakes were still hydraulic. Now, F1 uses a similar system called Energy Recovery System (ERS) which applies more friction and is allowed to gather more energy – around 120kW.

Because of this, teams were allowed to use a far more adjustable electronic braking system to better control the pressure applied to the rear brakes for more balance and stability. Front brakes remain hydraulic.

So how does this system work? When a driver brakes, the pedal still pressurises the master cylinder for the rear brakes hydraulically, but the physical connection ends there.

A computer measures the driver’ pedal pressure, and then takes into account both the front brake effectiveness and how much energy the Kinetic Motor Generator Unit (MGU-K) is able to harvest before reaching the 120kW storage capacity. The front/rear brake bias chosen by the driver via steeringwheel controls is also taken into account by the ECU.

While energy is being collected, the brakes will ease off to counterbalance the amount of retardation caused by the friction of the ERS. If the MGU-K is unable to gather any more energy, the rear brakes apply maximum possible pressure.

If the ECU which controls the rear brakes fails, there’ a backup line to the brakes, though its effectiveness is limited and unable to adjust itself. This did actually occur in the Canadian GP in 2014, when both Mercedes’ ERS failed and drivers were left using the backup hydraulics – delivering Daniel Ricciardo his first F1 GP victory.

The lower reliance on rear brakes has now meant engineers can use smaller (and therefore lighter) brakes at the rears, with some teams using four-piston calipers instead of six.

For example, in 2014 Red Bull, Mercedes, Sauber and McLaren all downsized their brakes in an effort to make the ever-valuable weight saving, though Mercedes would later swap back to using six-piston calipers.

Though brake-by-wire remains primarily the realm of F1 engineering, Alfa Romeo has taken it to the road with its Guilia’ braking system, known as Integrated Braking System (IBS). Though it numbs the driver’ sense of what’ happening at the corners of the car, like the pulsating effects of ABS for example, it also allows a more immediate reaction.

Mercedes also gave it a try in the early 2000s with Sensotronic, though it didn’ last long, and many Sensotronicequipped cars were recalled.