For reasons of safety, Formula 1’s technical regulations prescribe two separate braking circuits for the front and rear brakes so that, should one of them fail, the second braking circuit is still available. The brake discs may be up to 28 millimetres thick, and their diameter must not exceed 278mm. But the size of the brake is not nearly as important for its performance as its temperature. If the drivers brake hard from top speed, the brakes heat up to 1,000°C in less than a second. Below 400°C, carbon brakes are as good as useless, providing hardly any deceleration. They develop optimal traction at 650°C. This range needs to be achieved to make possible the spectacular braking manoeuvres that are decisive for a good performance on tracks with high brake wear, such as Monza or Montreal.

Maintaining the balance is difficult. If the brakes cool down too much, they do not provide enough friction, and if they are subjected to extreme temperatures for too long, they do not survive the entire race distance. This risk is especially high on the Circuit Gilles Villeneuve with its numerous high-speed straights and slow corners: the drivers accelerate to speeds of up to 320km/h on the straights, only to step hard on the brakes in time for the next chicane – before the brakes have cooled off after the strains of the last corner. “The challenging thing about Canada,” says

Dernie, “is keeping the brakes cool enough between the corners for them to provide optimal performance.”

Because liquid coolants are prohibited in Formula 1, the only means of keeping the temp-erature down is the air streaming through the brake cooling vents. Via holes in the brake discs, the so-called perforations, air is directed onto the discs and pads. The larger the holes are, the better the cooling effect is – however, the aerodynamics are adversely affected. Changing from the smallest to the largest holes, the ones used in Montreal, costs 1.5 percent of aerodynamic efficiency or one kilometre per hour of top speed. But aerodynamics aren’t everything. The engineers who vary the diameter of the holes according to the race track need to find the best possible balance between high deceleration and acceptable wear. “The braking process of a car is a highly complex matter,” says Gavin Fisher, Chief Designer for the BMW WilliamsF1 Team. “It takes the interplay between brakes, tyres and aerodynamic-ally generated downforce to guarantee ideal deceleration.”

Over the years, the requirements concerning the performance of brakes have also signifi-cantly increased for passenger cars, especially in the luxury range. “Vehicles with a top speed of 250km/h and a weight of two tonnes need to be able to dissipate very high kinetic forces in a minimum of time,” Dr. Christoph Lauterwasser of the Allianz Center for Tech-nology (AZT) explains. “Therefore, the lightest, low-maintenance brake discs, made of carbon-fibre reinforced ceramics, are a real alternative to steel in this segment.”

Despite all the available hi-tech, braking is still purely intuitive for Formula 1 drivers because ABS, which prevents the wheels from locking up, is prohibited. However, they can regulate the distribution of braking forces between the front and rear axles using a dial on the steering wheel. This adjustment of braking balance at least allows them to avoid the typical dipping of the front wheels when beginning to brake. Usually, 60 percent is distributed to the front axle, 40 percent going to the rear axle. Should the wheels lock up in spite of this, the load acting on a very small surface area means that wear is no longer evenly distributed all around the tyre – this is referred to as a braking puncture. As a result, the tyres no longer run smoothly and lap times increase. Due to the new regulations that allow a change of tyres only in the case of an obvious defect, this kind of mistake can ruin an entire race.

And did you know...

... that full braking requires the brake pedal to be actuated with a force equivalent to 80 kilogrammes? This demands well-trained leg muscles because at Monza, for example, the drivers have to brake hard 212 times. Doing so also subjects them to deceleration forces of up to 5G. This means that a head weighing six kilogrammes and a helmet weighing 1.5 kilogrammes together weigh five times as much, albeit for a brief period – so the neck muscles have to withstand a weight of 37.5 kilogrammes. By the way, brake boosters are not permitted in Formula 1.