Tread pattern

Snow and wet traction are highly dependent on the tread pattern. Although the tread pattern overwhelms the compound properties in significance, the latter can play a role in optimizing snow traction. Compounds using polymers with low glass-transition temperature, T (—40 to —OS " C), remain more flexible at low temperatures. Tread compounds with low complex modulus at 0—20°C have better snow traction. 

Laboratory measurements are primarily concerned with tread compound traction properties. Tread pattern and other tire parameters like cornering and longitudinal slip stiffness require still tests with tires on either large indoor machines or direct proving ground measurements. 

In tire tests, therefore, a stiffer tire construction reduces the wear. The stiffer construction not only includes the carcass and belt (i.e., height to width ratio), but also the tread pattern and the stiffness of the tread compound. Therefore, a correct road test requires two identical vehicles, each equipped with a test group of four identical tires. If this is not possible at least one axle has to have identical tires. If this is not the case an average slip will balance the acting force on the axle. This will be larger for the stiffer tire than is required if both tires had the same stiffness and smaller for the softer tire. Hence, the result is falsified to the advantage of the softer tire. The same argument holds for multi-section tires. 

The tire constmction influences both cornering and longitudinal slip stiffness. These include the tire carcass, breaker construction, inflation pressure, and tread pattern design. However, since the two stiffness components can be measured, knowledge of the construction details is not necessary. The vehicle geometry influences the tire wear through the air resistance, which it creates, and through the load distribution between front and rear axles. 

Tire Tire Construction kso(N/rad) = 60000 Tread Pattern Pattern width/tire width = 0.78... 

This basic mbber friction process is present on all surfaces, dry, wet or icy, being modified only by the external conditions. On wet surfaces this is primarily water lubrication which itself is influenced by the water depth, roughness of the road surface, and the state of the tire tread pattern. The low friction on ice near its melting point is mainly due to the properties of the ice. 

A narrow slit in the tread pattern of a pneumatic tyre, formed by fitting a thin blade in the mould often termed knife-cut . 

That portion of a vehicle tyre (pneumatic, semipneumatic or solid) which contacts the road surface. The tread pattern is so designed as to give the best combination of properties suitable for the conditions under which the tyre will be used. 

Other versions of the machine are designed for specific purposes, e.g., a twin ram machine capable of producing a continuous extrusion, and versions capable of applying tread rubber directly to a buffed tyre carcass whilst simultaneously forming the tread pattern. 

An extruder equipped with a reciprocating die forms the tread pattern directly onto the compound as it is applied to the casing. The casing is then vulcanised in an autoclave. 

A layer of retreaded rubber is formed on the casing and consolidated by pressure. The tread pattern is cut out of the applied rubber either in the same operation or subsequently. Vulcanisation takes place in an autoclave. 

Asymmetrical Tire design in which the tread pattern on one side of the centerline differs from that on the other side. 

For a truck tire, tread patterns can be classified into five basic types (Figure 14.15) ... 

FIGURE 14.15 Basic tread patterns (a) highway rib (b) highway rib/lug design (c) on/off highway (mixed service) (d) off highway. 

Rib designs with design elements principally in the circumferential direction are the most common type of tread pattern and show overall good service for all-wheel-position summer service. On heavy tmcks, they are used nearly exclusively on steer and trailer axles because of their lateral traction and uniform wear characteristics. Rib/lug combinations tend to find use on all-season tires, which require a balance of good tread wear, traction, and wet skid. On heavy-duty truck drive axles, where forward traction is a prime requirement and where fast tread wear occurs as a result of torque-induced slip, the highway lug design is required. For off-highway service conditions the tread pattern assumes a... 

TABLE 14.4 Automobile Tire Tread Pattern Classes... 

The ratio of net contact to gross tread surface area decreases as wet traction becomes more important. Tables 14.3 and 14.4 illustrate the net-to-gross percentage for various tire tread patterns. 

A number of additional terms are used to describe a tread pattern ... 

Pitch length Length of each repeating unit in a tread pattern. Variable pitch lengths in a tread design can be used to minimize noise. Pitch would be analogous to the wavelength of a sine wave. 

The tread pattern influences the ability of the tire to transmit driving forces, braking, and lateral forces while operating on a broad range of highway and off-road surfaces. The design of a tread pattern is essentially the separation or division of a smooth tread into smaller elements or blocks. These ele-... 

Pitch length Length of each repeating unit in a tread pattern. Variable pitch lengths in a... 

Knowledge of non-linear contributions to viscoelasticity is important for design of elastomer blends and composites for rolling resistance performance of tyres, hysteresis and heat build-up behaviour, and friction or grip characteristics. The importance extends beyond developing suitable blend and filler compositions, to the construction, geometry and tread pattern design of tyres to arrive at optimum performance. 

Among the various cost items in the operation of haulage vehicles, tyre wear is especially important. The rate of wear depends on several factors, including the tread pattern and the possible use of protective chains on severely abrasive rock terrain. 

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