The static coefficient of friction (between tire and the road surface), also known as the tire-road-interface friction coefficient, is determined by the vehicle's speed, the condition of the tires and the state of the road surface (see table above). The figures cited apply for concrete and tarmacadarn road surfaces in good condition. The coefficients of sliding friction (with wheel locked) are usually lower than the coefficients of static friction.Special rubber compounds providing friction coefficients of up to 1.8 are employed in racing tires.
AquaplaningAquaplaning (not aquaplanning), has a particularly dramatic influence on the contact between tire and road surface. It describes the state in which a layer of water separates the tire and the (wet) road surface. Aquaplaning phenomenon occurs when a wedge of water forces its way underneath the tire's contact patch and lifts it from the road. The tendency for aquaplaning is dependent upon such factors as the depth of the water on the road surface, the vehicle's speed, the tread pattern, the tread wear, and the load pressing the tire against the road surface. Wide tires are particularly susceptible to aquaplaning. It is not possible to steer or brake an aquaplaning vehicle, as its front wheels will have ceased to rotate, meaning that neither steering inputs nor braking forces can be transmitted to the road surface while aquaplaning. | 
