Tyre Thread Patterns or Designs

A tyre tread’s design is composed of five basic elements: tread blocks, grooves, sipes, cross slots and ribs. Grooves are channels that run circumferentially around the tyre between the tread ribs. Tread ribs are the raised section of tread pattern that are composed of tread blocks. Tread blocks are the raised rubber segments that make contact with the road surface. Cross slots are channels molded into tread elements to provide extra water evacuation. Finally, sipes are the small slits molded into the tread blocks that increase the number of biting edges to enhance all-season traction. [1]

Fig 1: Basic elements of tyre thread patterns [1]

Tyre thread pasterns / designs generally fall into one of the following categories:

• Symmetric
• Asymmetric
• Directional and Non-directional.

Tyre treads can be directional, non-directional, symmetric and asymmetric. Tyre threads are important for economy, good grip in all road condition, safety, comfort and speed.

a) Symmetric tread design can be commonly seen on the tyres of many cars. As their name itself indicates, symmetrical pattern refers to those treads which feature similar continuous design across the tread on either sides of tyre. Tyres with this type of pattern are normally non-directional, meaning that they can be fitted without worrying about a specific rotational direction.

Symmetric tyre thread

It features continuous ribs or independent tread blocks in the same arrangement along the entire circumference of the tyre. Symmetric tyres are quite popular in passenger cars and provide a good balance between wet and dry traction, while maintaining steering responsiveness

b) Asymmetric tyre treads are exactly opposite to the symmetric tread pattern –feature dissimilar designs on both the sides. This discrepancy in their design allows better grip on flat out roads and also while making turns. Generally, the outer area of such tyres has broad design whereas the inner carries smaller independent tread blocks, as seen on symmetric design.

Asymmetric tyre thread

One of the most popular tread patterns in passenger cars, this pattern is designed to optimise grip on both wet and dry surfaces, without one compromising the other. In this tread pattern, the outer tyre shoulder exhibits large and wide compact tread blocks that increase the contact patch on dry roads, resulting in better handling and increased steering responsiveness.

The purpose of this design is to evacuate the surface water lodged in the tread. Thus the contact patch between the surface and the tyre increases, resulting in increased resistance to aquaplaning and better wet handling characteristics.

c) Directional tread patterns are designed to provide a range of functions during particular driving conditions. The tyre can only be mounted to the wheel so that it revolves in a particular direction to correspond with the tread pattern. An arrow on the tyre sidewall indicates the designed direction of forward travel.

Unidirectional or directional tyre thread pattern

The directional (also known as unidirectional) tread patterns are made to perform well when fitted on a specified direction, this direction is generally marked with help of an arrow on the sidewalls. This type of tyres have ‘V’ shaped tread design which helps increasing aquaplaning resistance when the vehicle is running on high speeds, by efficiently cutting it through this unique pattern.

Tyres with directional tread pattern have unique V-shaped grooves that radiate outwards from the central tyre rib to either sides. Such tyres are particularly efficient in dispersing water when the vehicle is moving at high speeds and hence are suited for performance vehicles.

d) Non-directional tread patterns are designed in such a way that the tyre can be mounted on the road wheel for any direction of rotation.

Other Tyre Tread Patterns

Snow/Mud Tread Pattern

The tread pattern for snow tyres is characterised by the presence of numerous sipes which provides biting edges. It also has tread blocks with deep and wide grooves which enhance the traction on snow.

Mud terrain tyre tread pattern has large chunky tread blocks that dig into the mud and offer increased grip. Also the large open design enables the tyres to self-clean, getting rid of mud stuck in between the lugs.

Snow/mud tyres are not recommended for regular surfaces as they have a reduced contact patch that compromises traction on these roads. Besides their particular tread pattern makes these tyres very noisy on normal roads.

Next Article: "Tyre Selections & Properties"

References:

[1] Tire Thread Patterns_ bridgestonetire.com