Formula One teams spend vast amounts on research and development. They spend on aerodynamics, on construction with composite materials, and on wringing the maximum amount of power from their engines. We must, however, remember that in Formula One, tyres remain the largest single performance variable.
So, car tyres are car tyres, right? Not quite; road car and racing car tyres are distant relatives at best. Road car tyres are made to last, typically for a life of 16,000 kilometres or more. Formula One car tyres are made to last 200 kilometres at most, but they are made to be both light and strong. Their internal nylon and polyester structure, with its complicated weave pattern, is designed to handle much greater forces than a road car tyre faces. Let’s put it this way, no road car is likely to generate a tonne of downforce, or 5g of longitudinal load…or 4g lateral loadings.
F1 car tyres’ soft rubber mix is there to offer maximum grip, at the cost of a limited life. The tyres wear very quickly. They also become very hot but this is meant to happen – cold race tyres offer little grip. By way of example, the dry grooved tyres used until recently were designed to run at between 90 and 100 degrees Centigrade. Look carefully at the TV footage and you’ll see the cars’ tyres, pre-race, clad in special coverings, which are electrically heated. The need for heat explains why Formula One cars can be seen weaving from side to side on the way to the starting grid. The drivers are perfectly sober and they aren’t playing – they’re just warming their tyres.
Slick tyres, those with no tread at all, offer maximum grip. However, it was decided in 1998 that slicks be outlawed. Grooved tyres were made de rigeur, to help improve F1 racing as a spectator sport by reducing cornering speeds. This made life difficult for the tyre makers. The rules specified that all tyres had to have four continuous grooves at least 2.5 millimetres deep, spaced 50 millimetres apart. So, tyre manufacturers had to adopt harder rubber compounds, to maintain tyre integrity. By the 2009 season, slick tyres came back. The FIA, Formula One’s governing body, decided to use limits on F1 car aerodynamics as a means of keeping cornering speeds down.
How ‘soft’ or ‘hard’ the rubber compounds in F1 car tyres are, is varied by race, according to each track’s characteristics. For each Grand Prix race weekend, teams choose from two different compounds, and every driver must use both during the race. What makes the difference in the hardness of the different specifications? A change in the proportions of ingredients added to the rubber mix. Of these ingredients, the three main ones are sulphur, carbon and oil. In general, more oil equals a softer tyre compound.
Formula One car tyres are obviously run at the appropriate pressures. However, air pressure isn’t quite the right term. F1 car tyres are inflated with more nitrogen gas than air. This gas and air mixture is less susceptible to pressure loss and minimises the pressure differences that come about through temperature changes.
As will have become clear by now, there are huge differences between road car tyres and Formula One car tyres. They may share basic characteristics but the common denominators between them are certainly low on the scale.