Today's market offers an immense number of tires with an unimaginable variety of tread patterns. But actually the tread pattern isn't such a complicated and manifold thing.
According to the physics laws the best grip could be provided by a tire without any tread as it would have the largest contact area with the road surface. Such kind of tires (also called "slicks") are using on "Formula 1" bolides. But in the same time these tires have a significant shortcoming - they demonstrate their full potential only on the perfectly even road and in dry weather. If someone would use it while raining he likely would face to aquaplaning effect which causes the loss of control over vehicle due the slipping on the water surface.
To ensure that the water film is not formed between the tire and the road and in the same time the water is pushed out of the contact patch the special grooves are made on the tire. Their structure specifies the pattern of the tread.
At the moment there are three main types of tread patterns.
1. Non-directional treads
Symmetrical non-directional pattern is the most universal, averaged version of the tread. As a rule, such tires are suitable for moderate driving in both rain and dry weather. The absence of drainage grooves makes it difficult to remove water from the contact patch, while the block structure of the tread pattern makes such tires relatively noisy. With all the shortcomings, tires with such a pattern are durable and have a very affordable price.
2. Directional treads
A directional tread pattern is required for more efficient water drainage from the contact patch. When rotating, the wheel squeezes out water and keeps grip with the road. The rolling resistance of these tires is reduced, they produce less noise, but in the same time have two major drawbacks. First, they are much more expensive, and second, their effectiveness entirely depends on the direction of rotation of the wheel. Usually the correct direction is indicated by an arrow on the sidewall of the tire. If the tire is placed wrongly, the tire will not push the water out of the contact patch, but will admit it. This will greatly affect the quality of the traction with the road.
The tires with the asymmetrical pattern have the best grip characteristics both on wet and on dry roads. They combine the best features of the both previous tread types but have a very huge shortcoming - their price is too high.