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46 F1 – AUTO-PHYSICS

temperature. The mixture also retains the pressure longer than normal air would and is of real importance as a 20 percent drop in air pressure would result in a 15 percent reduction in the already short life of the tyre. Today’s teams have also developed a special mixture which not only maintains the pressure but also helps in cooling the tyre to prevent it from overheating.

It may be round, black and boring, but more often than not it is the differentiating factor between teams. In 1997, World Champion Damon Hill, racing then in a well below par Arrows, scored a historic second place finish for the Arrows team mainly due to the superior performance of the Bridgestone tyres, thus proving to a lot of people, that having an edge in tyre technology could make up for a slight difference in power.

This year, FIA’s decision to have a sole tyre supplier in Bridgestone came as a breath of fresh air to the teams after the 2005 United States Grand Prix Michelin fiasco. But the immediate thought was that the constructors already associated with Bridgestone had been dealt with a huge advantage, especially Ferrari. Instead, Bridgestone developed four completely new dry weather compounds – hard, medium, soft and super-soft – for the 2007 season.

But the tyres used today are completely different from those used in the Damon Hill era. The main difference being the use of slicks – tyres without grooves – which provided cars with much more reckless speed and with that came added danger. With the cars getting faster by the second every year, the FIA was left with no option but to bring in the four groove stipulation on the tyres, in 1998, and do away with the slicks as a safety measure. Now, the regulations specify that all tyres must have four continuous longitudinal grooves at least 2.5 mm deep and spaced 50 mm apart. These changes created several new challenges for the tyre manufacturers – especially ensuring the grooves’ integrity, in turn limiting the softness of rubber compounds used.

Winning Compound

As the only friction causing parts of a Formula One car, tyres play a crucial role in determining exactly how much speed each car acquires. BY RAHUL RAVINDRAN

The hardness or the softness of the tyre is based on the proportions of the three main components added to the rubber which are carbon, sulphur and oil. Simply put, the more oil content in the tyre, the softer it is, in turn providing more grip, allowing the driver to push the car round the corners that much further. The downside, though, is the shorter life of the softer compound. A normal road car tyre will last you anywhere between 80,000 and 100,000 km. The life of an F1 dry weather tyre is between 80 and 300 km, not enough to even last a race. For these tyres to function at the optimum level, though, they need to maintain a particular temperature ranging between 90 and 100 degrees Celsius. To maintain the temperature, the tyres are wrapped in blankets, removed only just before the car comes into the pits or the start of the race. This is why you will also find drivers heating the tyres by swerving around on the warm up lap of the race or while following the safety car. Another factor which cannot be overlooked is the gas used to fill the tyre. Unlike normal tyres, air is not used, instead, the Formula One tyres are inflated with a special, nitrogen-rich air mixture, designed to minimise variations in tyre pressure with

The regulations specified by the FIA for this season were that two suitable compounds would be handed to each team before the race weekend, and that both sets were to be used during the race. After the confusion over the hard and soft compounds in Albert Park during the first Grand Prix in Australia, the second from inside groove was painted white to denote the softer of the two compounds provided for each race weekend. One of the worst possible situations for a race driver remains ‘aquaplaning’ – the condition when a film of water builds up between the tyre and the road, meaning that the car has reduced grip and is effectively floating. To counter this, Bridgestone has also developed intermediate and wet weather tyres to negotiate the weather changes. The tread patterns of modern racing tyres are mathematically designed to scrub the film of water which infiltrates between the tyre contact area and the track. To prevent this, Bridgestone can change the wet weather tyre treading based on the track and climatic conditions. The teams are also free to use the wet and intermediate tyres as and when they feel fit, except during the practice sessions when they can use them only if the race director declares the track wet. With each circuit having its own twist in the tale, the tyre strategies have even proved to be the difference between first and second place. This year the competition is so close that the engineers not only have to plan the right pit stop strategy but also have to pick the right time to use the softer compounds. These changes might seem small and insignificant in the grand scheme of things, but it is the difference between winning and just finishing the race as was highlighted in this year’s much publicised Stepneygate saga, where it was rumoured that the mixture used to inflate the tyres by Ferrari was also part of the information leaked out to McLaren.

47 ALL SPORTS MAGAZINE, OCTOBER 2007

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very Formula One car is a piece of art and the intricate detailing is what makes it everyone’s ultimate dream machine. In recent years, engine and, moreover, aerodynamic developments have been hogging the media spotlight. But the tyres have always been the single most important performance variable.


'07 October Tyres