The simple tyre is one of the most complex parts of any race car, and one which the driver absolutely must understand if he wants to win.
Slick tyres come in many sizes and compounds. Softer compounds will give more grip, but can heat up and wear quicker. If this happens too quickly the tyre can lose grip, or fail, early in a race. As a result tyres have to be closely matched to the car, and sometimes even the circuit to get the best balance for performance throughout the race.
Race tyres should not be fitted and used to capacity immediately. There are two main reasons, the first being that the tyres will be coated with a release agent used to stop them sticking in the moulds when manufactured. A couple of laps at medium pace will scrub this coating off.
Next the tyres need to be built up to operating temperature evenly. This is usually done by driving three or four laps at up to 80% of race pace, being careful not to slide the car too much. Once up to temperature the tyres are allowed to cool gradually, often by taking one or two slow laps before returning to the pits. This process is usually undertaking in practice, leaving the tyres in perfect condition for the race. Failure to do this can lead to the tyres prematurely ‘graining’ or ‘delaminating’ in a race.
All races have a warm up lap (green flag lap) immediately the start. The driver needs to use this lap to get as much temperature into the tyres as possible. This is often done be weaving the car on the straights, although far more effective is loading the car (i.e. accelerating heavily) around the corners. This second method is more effective at warming rear as well as front tyres.
For the first two laps of a race the driver needs to be very aware that the tyres may not be up to full operating temperature, and most importantly, of four tyres on the car, one or two may be far lower than others. For example the right hand rear may be cooler and have less grip, which only becomes evident in the few left hand corners on a circuit. It is this that often leads to first and second corner incidents.
Once into the race the driver needs to maintain a good feel of the tyres, and compensate to ensure they are not overloaded and overheated early in the race as this will lead to loss of grip.
Providing everything is well, a good driver then needs to read his tyres to maintain maximum performance. All tyres have an optimum slip angle, which is the amount the tyres can ‘slide’ before losing grip. Understanding the mechanics of the tyres, including temperatures, pressures and slip characteristics will greatly improve a drivers performance.
In the wet slick tyres are useless. This is partly because their width of smooth rubber stops the water between them and the track surface dissipating, resulting in the tyre running on a thin film of water and aquaplaning. A groved tyre provides gaps for the water to be squeezed into. A slick tyre in the wet also fails to build up the heat needed to generate grip, and so even without aquaplaning will have much reduced grip (grooved ‘wet’ tyres are usually constructed using a softer compound rubber to compensate). Similarly, a wet tyre used in the dry will have less grip as the grooves mean there is less rubber in contact with the road. The reduction in rubber also results in the remaining rubber taking too much load in dry conditions, leading to overheating.