Stop & Go

By Allianz
May 24 2003

Braking in a Formula One car is a complicated procedure. This Allianz feature gives you an insight into the complexities of braking; the brakes, the track, tyres, all play a role in how a F1 driver brings his car to a halt.

 

 

 
Stop & Go
 
In Formula 1 a short braking distance not only guarantees fast lap times, but also safety. The driver needs the right timing for that decisive moment. He has to rely on high-tech brakes, the right tyres and a perfect set-up. In road traffic too, braking correctly is an art in itself and has to be practised.

Full throttle or full braking: for the race in Monaco, Formula 1 moves into a realm of extremes. The city circuit offers an impressive insight into the challenges presented to both driver and car: short straights, during which the car accelerates up to 290kph, quickly change into extremely slow corners like the 40kph Grand Hotel section of the circuit. The brakes, in particular, are subject to enormous stress, such as at the start-finish line, where a car’s speed has to be reduced from 272kph to 88kph.

Among other things, this right-hand corner, the Beau Rivage, demonstrates the unbelievable possibilities of Formula 1 technology: on a 100-metre long section the car slows down from 300kph to 100kph in under three seconds. Here, a driver is subject to deceleration forces of up to 4G, which is equivalent to four times his own body weight.
 
Graphic courtesy of Allianz Click on image for larger version
 

In Formula 1, disc brakes are used which are similar to those fitted to passenger cars. There are, however, some important differences. In Formula 1, brake discs are heated up to 1000 degrees Celsius within one second. Since the start of the ’90s, in order to achieve such exceptional durability, brake discs and pads have been made of high-tech composite carbon which is also lighter than the steel used for the brakes in passenger cars.

In order to avoid overheating, the majority of teams use drilled brake discs which allow for the passage of cooling air. According to its technical regulations, the FIA stipulates aluminium brake callipers with a maximum of six pistons and two brake pads per wheel. Nevertheless, technicians are pushed to the threshold: the brakes on an F1 car have to be replaced after each race.

An additional influencing factor with braking distance is the issue of tyres. The grooved tyres which have been stipulated for use in F1 since 1998 provide roughly 20 percent less in bearing surface than the previously used slicks. The introduction of the grooved tyres was intended to slow down the cars, because less grip means slower cornering speeds and greater braking distances. However, the tyre manufacturers succeeded in compensating for this with improved rubber compounds; the precise mixture for Formula 1 tyres is kept secret by both manufacturers Michelin and Bridgestone. Basically, the following applies: a softer tyre has better grip and therefore greater braking power; but this advantage has to be weighed up against a serious disadvantage – softer tyres wear out faster.

Something that can be used in a flexible manner by the Formula 1 teams to bring about greater braking performance is the wing set-up. Driving with more downforce or with steeply set wings not only increases cornering speed, it also serves to shorten braking distance. Teams with particularly powerful engines enjoy an advantage here, because the loss in speed generated by a steeper wing setting is compensated for by their straight-line performance advantage.

“The braking procedure in a Formula 1 car is an extremely complicated one,” said Gavin Fisher, Chief Designer at WilliamsF1, “it is the interplay between brakes, tyres and aerodynamically generated downforce that guarantees ideal deceleration.” Whatever the case, the way to success in Formula 1 is via braking distance – or as the drivers would put it – anyone can step on the gas, but it’s knowing when to brake that makes you a winner…

For everyday drivers, a decisive safety factor in road traffic apart from servicing the brakes is the driver’s own braking behaviour. The disc brakes on a normal passenger car – which are usually made of steel – are generally inspected as part of a regular service. Not only the brake pads, but also the brake discs can and do wear out. Apart from this, the brake fluid has to be replaced at least every two years; it may not be used up, but it absorbs water from the air. This causes the brake fluid’s boiling point to be lowered, which in turn can result in a breakdown in the system.

Braking correctly is an art that has to be practised. Indeed, situations in which a full braking manoeuvre is required only occur seldom in everyday traffic, but then, this is precisely what causes many car drivers to brake incorrectly in an emergency. “Nine out of 10 motorists don’t brake correctly in critical situations,” says Dr. Hartmuth Wolff, of the Allianz Center for Technology (AZT) in Munich. “This is then compounded by not keeping a safe distance behind the car in front.”

The Allianz expert recommends maximum braking for virtually all emergency situations: “This guarantees the shortest possible stopping distance.” The problem of maximum braking without an anti-lock braking system (ABS) is that the front wheels are likely to lock up and then you can not steer the car. For this reason, Dr. Wolff recommends: “Stay on the brake pedal as long as possible, but then, if necessary, release the brake just before any obstacles and steer around them.” However, this is not really something one can learn without having attended a driver-training course with professional instruction.

Knowing how to use ABS also has to be learnt. Hartmuth Wolff recommends that to start with, drivers familiarise themselves with ABS at a driving school. Those unfamiliar with the system tend to press more lightly, or even to reduce the braking force, when they first feel the brake pedal vibrating (a sign that the ABS is working) – this dramatically lengthens the braking distance. In cars equipped with ABS, you must step on the brake pedal even harder in emergency situations than in vehicles without it. Only then is the power of the system deployed to its best effect.

 
 
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