Tyres crucial at Indianapolis

After a year of abstinence in Formula 1, when a set of tyres had to last for both qualifying and the race and a change was only permitted in an emergency, drivers can now make the most of their tyres' performance again. In 2006, Formula 1 tyres are still a crucial factor in deciding between victory and defeat; performing with magical prowess while subjected to extreme loads.

By returning to the old tyre regulations – and so more frequent pit stops – Formula 1 has not only become more interesting but also safer. Now, the drivers are no longer tempted to continue driving on worn or damaged tyres and, in the worst-case scenario, risking an accident simply to avoid losing time with an unscheduled tyre change. But the new regulation is not a carte blanche for the drivers. "It's true that we can drive a bit more aggressively again," says Mark Webber, WilliamsF1 driver, "but of course we still have to make sure that we last the full distance with the tyres."

Before the hour of the strategists at the pit-lane wall arrives, the teams first have to settle the tyre issue. Given the range that is permitted by the tyre clauses in the Formula 1 regulations, they are really spoiled for choice. For a grand prix weekend, no less than seven sets of dry-weather tyres are available for the drivers, plus four sets of wet-weather tyres and three sets of so-called monsoon tyres, which guarantee the necessary safety even if the track is waterlogged by a sudden downpour. The WilliamsF1 tyre partner, Bridgestone, will produce about 60,000 tyres for its teams this year, and brings 1,200 tyres to the track for every grand prix.

Choosing the right tyres is an art in itself. Picking the wrong tyres can ruin a driver's chances completely. During free practice on the Friday, they have to find out which tyre compound is required on that particular track, and which best suits the car and the planned strategy. They then have to decide before qualifying which compound they will use for the rest of the grand prix weekend.

As a normal car driver, too, it is easy to be overwhelmed when buying tyres. "You should certainly consult a specialist dealer and observe a few basic rules," recommends Dr. Christoph Lauterwasser from the Allianz Centre for Technology (AZT). First of all, you should comply with the specifications regarding the speed category, the size and the load index. You should also pay attention to the DOT code, which shows the production date of the tyre. "If you try to save money on tyres, you're cutting corners in the wrong place. One should also always avoid a combination of summer and winter tyres. A mixture of tyres like that can lead to uncontrollable handling," adds Lauterwasser.

In contrast to everyday traffic, the tyres in Formula 1 are subjected to extreme loads. The cars accelerate from a standstill to 100km/h in 2.6 seconds. The rear tyres have to give the 700HP car enough grip on the tarmac to ensure the wheels do not spin when accelerating. The front tyres, on the other hand, do all the hard work during braking. In figures, given full braking from 200km/h, a Formula 1 car comes to rest within 55 metres, and the resulting braking forces apply a staggering 2.5 tonnes to the tyres in a longitudinal direction. The load is even higher in corners, where the tyres have to withstand lateral acceleration forces equivalent to about 2.2 tonnes with centrifugal forces of up to 3.2G. Even when driving in a straight line, unbelievable forces are applied to the tyres by the downforce generated by the wings. When the drivers are racing at 320km/h, the wings press the car down with a load of 1.6 tonnes at the rear and 1.1 tonnes at the front. The downforce from the wings is so great that, in theory, a Formula 1 car with a medium wing setting could drive upside down on the ceiling at a speed above just 150km/h.

The rubber compound of a Formula 1 tyre works optimally in a range from 70 to 95°C. If the tyres are cooler, they cannot develop enough grip and if they become hotter, they wear out too quickly. In the worst-case scenario, they develop blisters, which could lead to the tyre
bursting. To prevent that, the tyres – which consist of about 80 types of rubber and 250 other additives such as oils, steel, sulphur, zinc, polyester, resin and silicic acid – are subjected to strict quality checks at the factory.

It was also a novelty in Formula 1 history when a tyre manufacturer advised that its teams withdrew from the start for safety reasons at the United States Grand Prix in 2005. With just six cars, the race was a farce in sporting terms, but also proof that the motto "safety first"
stands above all other interests in Formula 1.

"There is a lack of harmony at this track. The extremely long straight and the windy infield do not fit together very well. We drive at full throttle for almost 25 seconds on the banked corner, and the fact that on the left there is a concrete wall instead of a run-off zone does not exactly give you a reassuring feeling. In my opinion, you definitely need gravel traps at some points, which are missing. One important safety factor is the so-called soft walls, which absorb part of the energy in the case of an impact and so minimise the risk of injuries."