Tires on Racing Cars

Car tires are more than just cushions for the wheels. They also give the car a good grip on slippery roads and keep it from sliding about when braking and cornering. The tread patterns running all around the tire have thin cuts in the rubber to sponge up surface water, and zigzag channels to pump the water out behind as the car rolls forward. On a wet road, a tire has to move more than one gallon (5 liters) of water a second to give needed grip. On perfectly dry roads, the treads are not needed. A smooth tire gives the greatest possible area of contact with the road, but if smooth tires are used on wet roads, the film of water builds up in front of the tires and underneath them and actually lifts them off the road surface, a condition known as "hydroplaning." In this situation, the driver will lose control of the car. Most cars have to function in all types of weather, so their tires must have tread, but racing cars make very few outings a year. If the track is dry, they run on smooth tires, called "slicks," to get the best grip on the roads. The extra wide tires and wheels give more grip than the average car, but in wet weather, the racer must change to treaded tires.