Success in Formula 1 does not depend solely on engine power. On manycircuits, the brakes are the decisive factor for good performance. At the Canadian Grand Prix on the Circuit Gilles Villeneuve, they play a key role.
Frank Dernie of the BMW WilliamsF1 Team says: “Only if you can rely onyour brakes, can you exploit the full performance potential of your racing car.”
In the early years of Formula 1, the brakes were made of steel. Since 1982, theyhave been manufactured from carbon, the carbon-fibre compound that is only roughly a quarter of the weight of steel. Because every gram counts when you arechasing hundredths of a second, this is a decisive advantage. In addition, carbondisplays good friction properties, allowing for more sudden and shorter braking.However, manufacturing the discs and pads from this hi-tech material is extremelycomplex and expensive. For several months, the moulding blanks are baked in anautoclave at temperatures of up to 2,500°C, under high pressure, while beingfumigated with methane. This is a costly procedure: a set of brakes costs around7,000 euros, but at best these last for only 350km.
For reasons of safety, Formula 1’s technical regulations prescribe two separatebraking circuits for the front and rear brakes so that, should one of them fail, thesecond braking circuit is still available. The brake discs may be up to 28millimetres thick, and their diameter must not exceed 278mm. But the size of thebrake is not nearly as important for its performance as its temperature. If thedrivers brake hard from top speed, the brakes heat up to 1,000°C in less than asecond. Below 400°C, carbon brakes are as good as useless, providing hardly anydeceleration. They develop optimal traction at 650°C. This range needs to beachieved to make possible the spectacular braking manoeuvres that are decisivefor a good performance on tracks with high brake wear, such as Monza orMontreal.
Maintaining the balance is difficult. If the brakes cool down too much, they do notprovide enough friction, and if they are subjected to extreme temperatures for toolong, they do not survive the entire race distance. This risk is especially high on theCircuit 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 stephard on the brakes in time for the next chicane – before the brakes have cooled offafter the strains of the last corner. “The challenging thing about Canada,” saysDernie, “is keeping the brakes cool enough between the corners for them to provide optimalperformance.”
Because liquid coolants are prohibited in Formula 1, the only means of keeping the temperaturedown is the air streaming through the brake cooling vents. Via holes in the brakediscs, the so-called perforations, air is directed onto the discs and pads. The larger the holesare, 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 percentof aerodynamic efficiency or one kilometre per hour of top speed. But aerodynamics aren’teverything. The engineers who vary the diameter of the holes according to the race trackneed to find the best possible balance between high deceleration and acceptable wear. “Thebraking process of a car is a highly complex matter,” says Gavin Fisher, Chief Designer forthe BMW WilliamsF1 Team. “It takes the interplay between brakes, tyres and aerodynamicallygenerated downforce to guarantee ideal deceleration.”
Over the years, the requirements concerning the performance of brakes have also significantlyincreased for passenger cars, especially in the luxury range. “Vehicles with a topspeed of 250km/h and a weight of two tonnes need to be able to dissipate very high kineticforces in a minimum of time,” Dr. Christoph Lauterwasser of the Allianz Center for Technology(AZT) explains. “Therefore, the lightest, low-maintenance brake discs, made ofcarbon-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 becauseABS, which prevents the wheels from locking up, is prohibited. However, they can regulatethe distribution of braking forces between the front and rear axles using a dial on the steeringwheel. This adjustment of braking balance at least allows them to avoid the typical dipping ofthe 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 actingon a very small surface area means that wear is no longer evenly distributed all around thetyre – this is referred to as a braking puncture. As a result, the tyres no longer run smoothlyand lap times increase. Due to the new regulations that allow a change of tyres only in thecase 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 80kilogrammes? This demands well-trained leg muscles because at Monza, for example, thedrivers have to brake hard 212 times. Doing so also subjects them to deceleration forces ofup to 5G. This means that a head weighing six kilogrammes and a helmet weighing 1.5kilogrammes together weigh five times as much, albeit for a brief period – so the neckmuscles have to withstand a weight of 37.5 kilogrammes. By the way, brake boosters are notpermitted in Formula 1.
