Complex tyre behavior is a direct result of the tyre construction. While looking much like a simple rubber doughnut attached to the rim, the tyre construction is vastly more complex, the two main functions of the tyre, is force generation in the road plane and suspension of the vehicle mass. The force generation is made possible by the rubber tread, causing a high friction coefficient with the road surface. The suspension of the vehicle mass is managed by the belt, radial cords and beads. The radial cords work like the spokes of a bicycle rim; a pretension must be exerted by pressurized air inside the tyre to carry the loads. Naturally, there are more areas to take into account when the combination of components for the tyre is to be selected and calculated. Areas such as comfort, traction and cornering are covered.
First and foremost a tyre must have an adequate load capacity and be able to transmit
Â¢ Brake and
Â¢ Lateral forces under all conditions.
The good old pneumatic tyre is now well over a hundred years old, and has not really changed much from its original concept. John Boyd Dunlop registered this pneumatic tyre with the British Patent Office in 1888 and is therefore generally considered to be its inventor. The pneumatic tyre is now an indispensable feature of our motorized society. Complex tyre behavior is a direct result of the tyre construction. The two main functions of the tyre, is force generation in the road plane and suspension of the vehicle mass. The force generation is made possible by the rubber tread, causing a high friction coefficient with the road surface. Naturally, there are more areas to take into account when the combination of components for the tyre is to be selected and calculated. Areas such as comfort, traction and cornering are covered. Market surveys carried out in Europe reveal that nowadays more than three quarters of all freight is transported by truck. In comparison, the next most popular mode of transport, the railway, carries only an eighth of the total.
From the cross ply to the radial tyre
After the invention of the pneumatic tyre, it was a further thirty years before the first crossply tyres were developed for commercial vehicles. Progress in commercial vehicle technology imposed substantial requirements on crossply tyres which - despite all the advances made - they were eventually unable to meet. There are very distinct differences in the construction of radial and cross ply tyres. Whereas the carrying air container on crossply tyres is made from criss crossing layers of rubberized fabric, on radial tyres it is formed by radially running plies (casing plies) of rubberized cord (on commercial vehicle tyres steel cord is normally used). A so-called belt, made up of 3-5 rubberized steel cord belt plies, prevents or reduces tread deformation caused by tyre deflection or swelling when the tyre is inflated. On firm road surfaces the radial tyre is superior to the crossply tyre in many ways. One of the strong points of the crossply tyre, however, is its good self cleaning tread pattern; its stiffer sidewalls also enhance resistance to tipping on vehicles with a high centre of gravity, such as cranes. The radial tyre, however, definitely dominates today's truck sector.
It was only with the introduction of the radial tyre concept, where substantially improved design and Materials meant the tyre could meet the necessary requirements, that development was able to progress and reach the standards we have today.
The materials that make up a truck tyre
A tyre comprises different components, all of which contain elements in varying compositions. These elements vary with the size and type of tyre. Listed in the example below are the elements used
2. TYRE COMPONENTS AND THEIR FUNCTIONS
1 Tread strip
Material; Rubber compound
Function The tread strip has to provide high wear resistance and good grip under all road conditions. In some instances the tread strip combines two different materials (cap and base); the base is there to minimize the tread temperature and the rolling resistance.
2 Multi-ply steel belts
Material Steel cords embedded in rubber compound
Function Enhances driving stability reduces rolling resistance and gives the tyre its long service life. Restricts casing growth and increases the tyre's structural strength.
3 Steel casing
Material Steel cord
Function Gives the tyre its structural strength and its deflection characteristics; substantially determines driving comfort.
4. Inner lining
Material Rubber compound
Function Major factor in preventing diffusion of air and moisture in tubeless tyres.
Material Rubber compound
Function Protects from lateral scuffing and the effects of the weather.
6 .Bead reinforcement
Material Nylon, aramide, steel cord
Function Securing the end of the steel cord ply on the bead core. Reinforcing the bead against high shear forces.
7 .Bead core
Material Steel wire embedded in rubber compound
Function Ensures the tyre sits firmly on the rim.
3. TYRE MANUFACTURING
Supplier industries and manufacturing compounds
The tyre industry draws its raw materials from various sectors of industry. After appropriate pre-treatment, these materials are then further processed to form individual semi-finished products.
The steel industry
Provides high tensile steel, the basic material used in the manufacture of the belt and the casing (steel cord), as well as in the bead cores (steel wire).
The chemical industry
Supplies a variety of raw materials and accessory agents needed in tyre manufacture. These are primarily various synthetic rubbers and additives, which affect, for example, the tires wear resistance, grip and ageing stability.
Is extracted from specific trees by cutting into the bark. The milky-like liquid (latex) clots when acids are added and, once it has been washed with water, it is pressed to form solid bales.
The textile industry
Provides the basic materials for cord manufacture: rayon, nylon, polyester and aramide fibers. These are used, for example, to manufacture bead reinforcements. Natural and synthetic rubber bales are divided up, appropriate quantities measured out, weighed and mixed with other additives in several stages, in accordance with strictly specified recipes. More than ten different natural rubber compounds are processed to form the individual components of modern tyres. These individual tyre components and their functions are described in detail on pages 10 and 11.
4. MANUFACTURE OF SEMI-FINISHED PRODUCTS
Steel cord, pre-treated and delivered on bobbins, is fed into a calender via special coiling devices. It is then embedded in one or more layers of natural rubber. Depending on the tyre size, this continuous belt is cut at a specific angle and to specified dimensions using guillotine shears; it is then rolled up for further transport.
The ductile material manufactured in the mixing plant is extruded to form a continuous strip. After extrusion, the weight is checked and the tread strip immersed in a cooling tank. Once it has been cut to the required lengths the weight is re-checked.
A number of individual textile fibers are fed into the calender via special coiling devices and then embedded in a thin layer of natural rubber. This continuous belt is cut to the required widths on the shearing machine and rolled up for further transport.
Steel bead core
The core of a tyre bead is made up of several steel wires, shaped to form a ring and individually coated with rubber. This ring is then additionally covered with a core profile made from rubber compound.
The extruder is used to produce sidewall patterns featuring different geometry, depending on the tyre size. The inner lining is impermeable to gases and is extruded on the calender to a wide, thin layer.
Assembly and vulcanization
The semi-finished products manufactured in the various individual stages referred to above are gathered on the assembly machine and combined in two stages (casing and tread layer) to form a moulded blank. Before being vulcanized, the moulded blank" is sprayed with a special liquid. In the vulcanization press heat, pressure and time give it its final shape.
Final quality controls and dispatch
After vulcanization, the tyres are checked optically and undergo various other checks. Once the tyres have passed all the tests, they are taken to the delivery warehouse to be prepared for dispatch.
5. LEGAL AND STANDARDIZED MARKINGS USED ON THE TYRE SIDEWALL
(Brand name or logo)
1a Tread pattern reference
2 Size designations
315 = tyre width in mm
80 = aspect ratio (section Height to section width) =80%
R = radial construction
22.5 = rim diameter (code)
3 Service descriptions
Consisting of 154 = load index for single fitment
150 = load index for dual fitment
L = code letter for speed rating
4 Country of manufacture
5 US load designation
Of single/dual fitment and indication of max. Inflation pressure in psi (1 bar = 14.5 psi)
5a Load range
In accordance with US standard
6 Data as per US safety standard
On inner construction or number of plies, in this case
Tread: under the tread there are five steel cord plies (including carcass)
Sidewall: viewed from the side there is one steel cord ply (in this case the carcass ply)
Tread Wear Indicator
8 Recommended applications
Only Continental Truck Tyres
The manufacturer has designed the tyre for regrooving
11 E = tyres complies with value set forth in ECE-R 54
4 = country code for the country in which the approval number was issued
(Here: 4 = Netherlands)
12 DOT = U.S. Department of Transportation
(Responsible for tyre safety standards)
13 Manufacturer code:
Â¢ Tyre factory
Â¢ Tyre size
Â¢ Tyre model
Â¢ Date of manufacture
The most important markings
315/80 R 22.5 154/150 M 156/150 L tubeless
315 - Tyre width in mm
80 - Cross-sectional ratio H: W in %
R - Radial design
22.5 - nominal rim diameter of 15Ã‚Â° tapered rim (code)
154 3750 kg tyre load capacity S (single tyre fitment)
150 3350 kg tyre load capacity Tw (twin tyre fitment)
M Speed 130 km/h (81 mph) (156/150)L
Alternative permitted operating code tubeless
6. TYRE TIPS
The following requirements are law in the majority of European countries:
Â¢ Pneumatic tyres on trucks and trailers have to feature tread grooves or sipes round their entire circumference and over the whole width of the tread area.
Â¢ The main grooves on truck tyres have to have a tread depth of at least 1 mm, 1.6 mm or 2 mm, depending on the law in each country. The limit in the UK is 1mm.
The depth of the tread pattern is to be measured in the grooves or sipes; bridge-like protrusions or reinforcements in the tread base should be ignored in this context.
Â¢ On tyres with wear indicators (TWI = Tread Wear Indicators), the tread depth should be measured in the grooves where the wear indicators are located.
Wear indicators on commercial vehicle tyres are bridge-like protrusions 1.6 mm high, which show whether the tyre has reached the wear limit.
The tread depth should therefore never be measured on the wear indicators, but next to them.
One of the most important causes of excessive tyre wear and damage is incorrect tyre pressure. Service manuals produced by the vehicle manufacturers and technical documentation from the tyre manufacturers provide information about correct tyre pressure. These values apply without
exception to the cold tyre, as the inner pressure of the tyre increases in operation.
Tyre pressure should be checked every 2 weeks, at the latest every 4, on the cold tyre. Spare tyres must also be checked.
Under inflation leads to
Â¢ increased flexing, which makes the tyre overheat and may cause tyre failure;
Â¢ increased wear = shorter service life;
Â¢ Higher rolling resistance and subsequently increased fuel consumption;
Â¢ Irregular wear.
Tyres which can be regrooved are designated
On the sidewall area. These tyres feature an additional rubber layer between the belt sector and the tread grooves, which is currently between 2 and 4 mm depending on the tyre size and tread pattern. This rubber layer can be used to achieve a longer tyre service life by having the tyre regrooved once the appropriate wear limit is reached on the original tread pattern. A basic continuous layer of 2 mm must still cover the belt.
A 50 per cent reduction in the depth of tread on a new tyre produces a 20 per cent improvement on rolling resistance. This means that less power is required to drive a car for a given speed that leads to less fuel consumption. The reduced power requirement also means a reduction in harmful exhaust emissions escaping into the environment. While motorists may prefer to have a deeper tread depth for a longer tyre life, they may not be prepared for the extra fuel consumption that the 20 per cent worsening of rolling resistance represents.
1. INTRODUCTION 1
2. TYRE COMPONENTS AND THEIR FUNCTIONS 4
3. TYRE MANUFACTURING 6
4. MANUFACTURE OF SEMI-FINISHED PRODUCTS 8
5. LEGAL AND STANDARDIZED MARKINGS 11
6. TYRE TIPS 15
7. REGROOVING 17
8. CONCLUSION 18
9. BIBLIOGRAPHY 19