A tire or tyre is a device covering the circumference of a wheel. It is an essential part of most ground vehicles and is used to dampen the oscillations caused by irregularities in the road surface, to protect the wheel from wear and tear as well as to provide a high-friction bond between the vehicle and the ground to improve acceleration and handling. Today most tires, especially those fitted to motor vehicles, are manufactured from synthetic rubber, but other materials such as steel may be used. The grooves or treads found in most tires are there to improve contact between the tire and the road in wet conditions. Without such grooves, the water on the surface of the road would be unable to escape out to the sides of the wheel as the tire presses down onto the road. This causes a thin layer of water to remain between the road and the tire's surface, which causes a severe loss of grip. At higher speeds, this can cause hydroplaning, substantially reducing traction during braking, cornering and hard acceleration. The grooves in the tread provide an escape path for the water - and it is even claimed by some tire manufacturers that their tread pattern is designed to actively pump water out from under the tire by the action of the tread flexing.