Chapter Two:Tire Composition, Mark and Specification

Chapter Two:Tire Composition, Mark and Specification


Section 1 Composition of tire



  A tire consists of cover, inner tube, and flap. These three things are used together with the rim. A cover consists of three main parts: carcass, tread, and bead. The carcass includes two parts of ply and breaker, and the outer rubber includes two parts of a tread rubber and a side rubber.


1. Tread

The tread is the cover layer of the tire. The tread rubber is divided into two layers: the crown rubber and the tread slab base rubber. Crown rubber directly contacts the ground, has wear resistance and cutting resistance, and it can conduct the traction and braking force of wheels. The tread slab base rubber at the bottom of the pattern is used to buffer the vibration and impact conducted by the ground, which is usually made of rubber with heat resistance and shear resistance different from the crown rubber.


2. Carcass

The carcass multi layer hanging rubber cord according to a certain angle,semi-rigid frame, which can hold compressed air, has the required strength and elasticity to bear the complex stress and deformation when the tire is used, and mitigate the external road vibration and impact. Radial ply is the skeleton of the carcass, supporting all parts of the outer tube, and also fixing the outer contour of the outer tube. The buffer layer is located between the carcass ply and the tread, and there are two forms of cord and film. The sidewall can protect the body and body of the tire from damage and has a certain flexibility.


3. Bead

The purpose of the bead is to tightly fix the tire on the rim and to withstand various forces of the tire and the rim. The traveler is the foundation of the tire bead and an important part of the strength of the tire. Its structure is divided into four sections: square, hexagonal, semi-circular and circular.


4. Inner tube

The inner tube is a elastic circular rubber tube, which can stretch and cling to the inner cavity of the outer tube when inflated, thus sealing the air. It has high elasticity, tear resistance, fatigue resistance and excellent air tightness.The size of the outer edge of the inner tube is smaller than that of the inner cavity of the outer tube. The thickness of each part of the cross-section is different from the use conditions such as inflation, and the crown part or the combined part is often thicker than other parts. The inner wall of a tubeless tire is lined with an airtight layer, which is equivalent to the tube of a tubed tire.

According to the structure, the valve of the inner tube can be divided into three categories: rubber metal valve (mainly used for car tires), rubber valve (mainly used on inner tube of truck tire) and water and gas dual-purpose valve (on special vehicle inner tube) . The valve of the tubeless tire is fixed directly on the rim.


5. Flap

Flap is placed on the contact area between the inner tube and the rim to protect the inner tube from abrasion of the rim assembly. According to the structure, the flap is divided into three types: formal, Formless and flat belt. The edge of flap is thin, the surface is smooth, and it has heat resistance.


Section 2 tread pattern


Different tread patterns have different degrees of traction, cutting resistance, wear resistance, heat resistance and floatability. Therefore, the choice of tread pattern of engineering tire depends on the working properties and conditions.


1. Rock pattern

Rock pattern is specially designed to prevent sharp rock cutting. It has a wide grounding area and excellent wear resistance, as shown in the figure.



2. Traction pattern



Type PI

The traction pattern is a directional pattern. The pattern on the driving wheel is to one side to produce good traction, while the pattern on the follower is to the opposite direction. On the driving wheel, the pattern block has the self-cleaning effect and improves the traction. The large and deep groove can produce high traction. However, due to the small grounding area, the cutting resistance and wear resistance rather than the rock pattern.


3. Block pattern




Type MP

  The block pattern has a wide tread and a flat shoulder under heavy load. Due to its high grounding area, the pattern has low grounding pressure and high floating force, which is suitable for soft ground.


4. Striped pattern




Type ST-1

  The groove of the stripe pattern is parallel to the driving direction and has high directional stability. This kind of tire is mostly used on the free rolling wheel.


5. smooth pattern




  The smooth surface tire has no pattern groove and is used for low-level trailers. Because of its high abrasion resistance, it is often used in underground mining carriers. There are usually two grooves on a smooth tire for a carrier, which is used to measure the degree of tread wear.


6. Comparison of normal, deep tread and deepened tread

The deep and deepened pattern heights are 1.5 and 2.5 times higher than the normal pattern heights, respectively. The overall diameter of the deep and deepened tread tire is almost the same, but larger than the tire diameter of the normal tread. When replacing a regular tread tire with a deep tread tire or a deep tread tire, the larger outer diameter of the tire and the thicker tread thickness should be considered.


Section 3 Tire specification


There are two methods of tire size marking: the traditional and the international. The traditional method is to mark the tire with two groups of numbers connected by a half line. The first group of numbers indicates the section width of the tire, and the second group of numbers indicates the rim diameter, all units are inches (1in = 0.0254m). Some also add ply levels, indicated by the symbol "PR". If it is a radial tire structure, The halfword line connecting two groups of numbers is usually replaced by R (Radiol for meridian structure). The profile of tire is evolving and developing, which is divided into common profile tire, wide base tire and low profile tire. The profile is shown as follows:




1. Specifications

(1) Specification and characteristics of common cross-section tires:

Example: 27.00 –49 – 48 PR (Construction Machinery Tires --- common Sections)

27.00 ------- Section width code 27 inches

(27.00 is the expression method of ordinary cross-section tire)

49 -------- Rim diameter code 49 inches

48 -------- number of plies of tires

PR -------- The ply rating of the tire (abbreviation of PLY RATING)

Features: Good ground area and average pressure, suitable for uneven and hard soil roads.

Uses: For large dump trucks, but also for small loaders and bulldozers.


(2) Specification and characteristics of wide-base tires:

Wide base tires are currently known as wide rim tires in China, with a cross-section width of 14 inches or more.

Ex: 23.5 – 25 – 16 PR (Construction Machinery Tires --- Wide Base)

23.5 ------ Section width code 23.5 inches

    (23.5 is the representation method for wide base section tires)

25 ------ 25 inch diameter of rim

16 ------ number of plies

PR ------ The ply rating of the tire (abbreviation of PLY RATING)

Features: Large ground area, low average pressure, suitable for soft ground, large buoyancy, small sinking, and good lateral stability.

Uses: Used in scrapers and large loaders.


(3) Specification and characteristics of low-profile tires:

Such as: 35/65 – 33 – 30 PR (construction machinery tires --- 65 series low profile)

35 ------ section width code 35 inches

65 ------  cross-section aspect ratio (flat ratio%)

33 ------  diameter 33 inches of rim

30 ------  number of plies

PR ------ The ply rating of the tire (abbreviation of PLY RATING)

Features: Large ground area, small average pressure, suitable for special ground operations, large buoyancy, small sinking, and good stability.

Uses: For scrapers and loaders with special requirements.