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What technologies are deployed to make a tyre?

ABC of tyre

Round and simple

Tyres have a vital role as the only part of the vehicle that touches the ground. That sets various, and sometimes competing, requirements for their performance. Tyres must strike a balance between traction, durability, energy efficiency and comfort, in addition to be superior and safe in their particular use situations and in all weathers. Hence, it is no wonder that tyres are more complex to design and manufacture than you would expect.

Ambitious designing

New tyre development is a highly complex and innovative process, which involves a multi-disciplinary team of designers and engineers with special expertise, such as tire pattern design, material development, prototyping, testing, and tyre mould design. Besides innovation, discipline is needed amid the growing requirements and tightening standards of the industry.

B as blending

Myriad ingredients including different kinds of natural and synthetic rubber, fillers, plastifiers, chemical additives and reinforcements – over 200 raw materials in total – are mixed in giant blenders to create a homogenised compound. Each material contributes certain properties to the compound, such as top performance, traction, safety and sustainability.

C as calendering

One of the oldest rubber processing technologies is calendering, a mechanical process by which rubber is pressed into fabric or steel cords, forming composite sheets for casing, cap plies and chafers. There are several types of rubber calenders with a different number of rolls positioned either vertically or horizontally. Calendering helps to prepare compounded rubber as a composite sheet of definite thickness and width, by placing a thin coat of rubber on a fabric, and forcing rubber into the interstices of fabric by frictioning it.

At this point, it is time for to start the engines and start production.

B as building

The inner liner, body plies, sidewalls, belts and finally the tread band are placed in a tyre-building machine, which pre-shapes the tyres into a form very close to their final dimension. All of the various components need to be positioned correctly before the tyre goes into the mould.

C as curing

In a curing machine, the green (uncured) tyre is vulcanised with hot moulds at over 300 degrees. All parts of the tyre are compressed together. Now the tyre gets its final shape, tread pattern and sidewall tyre markings.

After curing, finishing operations and inspections are performed before the tyre is ready for storing or distribution.

B as balance

In tyre balance measurement, the tyre is automatically located on wheel halves, rotated at a high speed and tested for imbalance.

C as control

Finally in quality control, professional tyre inspectors check each tyre carefully looking for slightest imperfections. Special machines help in finding flaws, if any, while the inspectors’ trained eyes and hands catch others. Some tyres are x-rayed to ensure tyre integrity or even cut apart for studying every detail of their construction.

What is a tyre?

How would a two- or four-wheeled vehicle look like without its tyres? Naked and abandoned? Definitely incompetent to complete its task. Simply said: the tyre is the only part of the vehicle that touches the ground. This mundane fact makes one understand the vital role of tyres in vehicle safety and performance. Their traction determines your ability to turn, brake, accelerate, or to stay stably on the road at higher speeds and on wet or frozen surfaces.

What are the types of tyre constructions?

After taking a first look at the structure of different agricultural tyres, we already realize that there are remarkable differences between them.

Tyres are engineered in different ways to ensure the best possible performance of the vehicle in each purpose, on different surfaces and with specific applications. The two main types of tyre constructions are radial and bias tyres.

Radial Tyre:

In a radial tyre,the cords in the carcass are arranged at a 90° angle to thecenterline of the tread – appearing to radiate from the centerline. Radial tyres also use multi-layer belts placed circumferentially around the casing, under the tread. They are independent from the body plies, and so cause a discontinuity where the sidewall and tread meet. Thus, because the tread and the sidewall function independently, the steel belts provide stability for the tread without losing in flexibility in the sidewalls.

Caption 1: The ply cords are laid at a 90° angle to the centerline of the tread. The tread and the sidewall function independently.

 

Bias:

Bias tyres, also known as bias ply or diagonal tyres, are made out of a single working unit. They consist of multiple layers, plies,which are laid at alternate anglesto the tread centre line. The plies can be constructed of various materials including rubber, steel, nylon and fiberglass, or of a combination of all these.This construction method makes the sidewalls of bias ply tyres strong and stable, but less flexible.

Caption 2: Multiple ply cords are laid at alternate angles to tread centerline, extending from bead to bead. The tread and the sidewall are integrated.

 

Bias belted:

Bias belted tyres are a hybrid combination having the structure of bias tyres combined withsteel belts like a radial tire. Hence, they have a wider tread area and more flexible sidewalls than bias tyres, but they hardly compete with radial tyres in roadability, handling and service life.

Caption 3: Bias-structured tyre with steel belts protecting the tyre carcass.

What are the different types of tyres?

In addition to different ply construction, there are different types of tyre tread designs. In principle, the designs with a less aggressive tread pattern are more suitable for working on lawns or in situations where the soil must be protected. Conversely, more aggressive patterns provide better traction in farm field conditions.

Agricultural R1, R1W, R2, R3

Agricultural rear tyres (R1-R3) are preferred for general farming. R1 tyres are a good option if the conditions are mostly dry, whereas R1W tyres – deeper than R1 – serve better in marginal soil where moisture content is greater. These tyres offer the best transfer of your tractor's power in the field. R2 tyres are particularly designed for farming in wet and difficult conditions with their deep tread and a more-severe tread angle. R3 tyres – also known as turf tyres – are ideal for farming sandy or volcanic ash soils, or when there is a great need to minimize soil disturbance, such as in golf courses.

Agricultural F1, F2, F2M, F3

Front tyres can come in the above styles, but special ribbed tyres are often the preferred style. There are tyres with single, three, four and five ribs, and each of them has its own advantages.

Flotation tyres

Flotation tyres are designed for a wide range of machines and implements that need high load capacity, albeit have lowest possible ground pressure and minimal crop damage. Flotation tyres are produced in both radial and bias construction, providing optimized solutions for different terrains and various applications, ranging from heavy-duty vehicles to light-duty equipment. 

Recently, the popularity of flotation tyres has grown parallely with the increased concern about soil compaction. Wide flotation tyres effectively prevent rutting, and thus, soil compaction. Due to their lower rolling resistance, they are also soft on soil and better for your wallet.
 

Implement I1, I2, I3

Tyres for two-wheel drive tractors and implements can be used on a variety of agricultural equipment. I1-type rib-tread tyres are a generally safe choice for any towed equipment. The button-style tread of I2 tyres makes them a particularly good choice for operating in moist and muddy fields. I3 tyres are commonly used on self-propelled implements and ground-powered equipment.
 

What are the various applications of agricultural tyres?

Agricultural tyres are used in multiple applications, ranging from huge tractors and combines to trailers and sprayers. Common for all, the success of a working day relies much on their performance.   

  • Tractor tyres: tractors and sprayers
  • Harvester tyres: harvesters, combine harvesters
  • Implement tyres: Tyres for trailers and agricultural machines, such as spreaders, tankers and grain carts
  • Tyres for soil preparation and irrigation machines
  • Agro-industrial tyres: Telescopic handlers, backhoes and loaders
  • Light-service tyres: hobby machines, such as lawn and garden tractors 
     
Tyre markings

A tyre sidewall has myriad texts, numbers, marks and pictograms on it. These codes are known as tyre markings. They share important information about the structure, dimensions, possible applications and the identity of the tyre.

 

A little TyrEncyclopedia

A1-A8Speed symbols for 5-40 km/h (see table x)
AMPTAgricultural Multi Purpose Tyre (for a high rate of road service max 65 km/h)
AGROFORESTTyres for mixed agricultural and forestry use
BBias belted construction (for example, 520/70B30)
BSpeed symbol for 50 km/h (see table x)
CSpeed symbol for 60 km/h (see table x)
CValve type
DSpeed symbol for 65 km/h (see table x)
ESpeed symbol for 70 km/h (see table x)
FSpeed symbol for 80 km/h (see table x)
JSpeed symbol for 100 km/h (see table x)
LValve type
LILoad Index (tyre load capacity at nominal maximum speed)
ODOverall Diameter (of an unloaded tyre)
PRPly Rating (strength code for the tyre carcass)
RRadial construction (e.g. 710/70R38)
RIMRecommended rim (gives the best fitment for all conditions and uses)
RIM (PERMITTED)Permitted rim in addition to the recommended rim
RCRolling Circumference (in mm, at reference load and pressure)
SLRStatic Loaded Radius (from wheel center to the ground at reference load and pressure)
SRISpeed Radius Index (theoretical)
SSSpeed Symbol (indicates the nominal maximum speed of the tyre)
SWSection Width (in mm, unloaded tyre)
TAir-water type valve
TLTubeless
ZScrew-on universal type valve
Elements of Tyres and their Functions

Inner Liner

The modern version of an inner tube is an extruded rubber sheet compounded with additives that result in low air permeability. It is resistant to air and moisture penetration and assures that the tyre will hold high-pressure air inside.

Body Ply

A calendered sheet of two or more bonded sheets consisting of consecutive layers of rubber and reinforcing fabric like nylon or polyester. These layers make up the tyre’s skeleton. They are highly flexible but relatively inelastic. A layer called the carcass ply placed directly above the inner liner, gives the tyre its strength and helps it resist pressure. Heavy tyres have progressively more plies that give structural strength to the tyre.

Sidewall

The area of extra-thick rubber that runs from the bead to the tread and gives the tyre good abrasion resistance and its lateral stability. Additives protect the tyre from decomposition when exposed to UV light. Sidewall contains important tyre markings, such as size and speed category.

Beads

Bands of high tensile-strong steel wire coated in a rubber compound. Coatings protect the steel from corrosion and improve the bonding of the bead to the rubber. Beads are inflexible and inelastic, and provide mechanical strength to keep the tyre properly seated on the rim.

Apex (filler)

A triangular extruded profile that mates against the bead. The apex provides a cushion between the rigid bead and the flexible inner liner and body ply assembly.

Belts (crown plies)

Calendered sheets consisting of layers of rubber and a layer of steel cords, which are oriented radially in radial tyres, and at opposing angles in bias tyres. Belts give the tyre strength, rigidity and puncture resistance without sacrificing flexibility, needed to absorb deformations at bumpy surfaces.

Tread

A thick extruded profile that surrounds the tyre carcass and gets directly in contact with the road. Tread compounds include additives to impart wear resistance and traction in addition to environmental resistance. Hard compounds have long wear characteristics but poor traction whereas soft compounds have good traction but poor wear characteristics. The design and compound of the tread determine many of the tyre’s most important performance features.