Directional tyres are those that have a tread pattern designed to operate best when rotating in one specified direction. The tyre pattern is usually chevron or arrow-shaped with grooves running from the central portion of the tyre to its shoulders. Generally acknowledged to be derived from wet racing tyres, these directional road tyres have excellent wet weather grip due to their increased ability to remove water from the road surface.
Directional tyres will usually be marked with an arrow or other symbol to indicating the direction in which they are designed to run.
A strong point of a directional tyre is its ability to resist aquaplaning. However, due the fairly aggressive tread design they are generally thought to suffer from higher noise generation than non-directional tyres. Care must be taken to mount the tyre correctly on the rim as performance can be reduced dramatically should the direction be incorrect. A directional tyre on a spare wheel has a 50/50 chance of being in the wrong direction of rotation when fitted in an emergency!
Picture shows a typical directional tread pattern