A tractor wheel is a complex combination of numerous components providing it with both the rigidity and tyre-to-ground contact adapted to its use.
The radial structure is currently more widely used in the farming industry (IF VF technology) than the diagonal structure.
The casing of radial tyre
The structure of a tyre starts with its casing. This casing is a mixture of synthetic textile cords and steel wires covered in brass and plaited together. Its job is to withstand the load that an agricultural tyre has to bear.
The orientation of these cord layers determines the type of tyre. For a radial tyre, they are organised perpendicularly in relation to the running direction.
This positioning allows for increased deformability of the sidewalls, specific to radial tyres. Shocks are better absorbed, and the comfort level is higher.
In addition, the internal surface of the casing is covered with a layer of rubber which has been treated to guarantee the water tightness of the tractor tyre and to maintain the pressure level.
Stability plies of radial tyre
On the upper part of the casing, additional layers are placed diagonally to the running direction, they are the stability plies.
There are two types of plies: on the one hand the radial plies (just above the casing) which provide reinforcement and on the other hand the cap plies which strengthen the tread.
Their job is to provide directional stability and to enable the tyre structure to work across its full width. They also absorb some knocks and protect the casing from external damage.
Tyre beads of radial tyre
The casing is reinforced at the joint with the wheel rim, by metal rings (one on each side of the tractor wheel), known as tyre beads.
These beads maintain the casing plies by stiffening the bead heel for good guidance of the tyre and high-quality transmission of traction between the rim and the tyre.
The sidewalls of radial tyre
The external surface of the agricultural tyre is completely covered in rubber, this is the visible part of the assembly.
The resistance of this rubber to wear and cuts protects the casing and the plies from external damage.
A thin and smooth layer is first placed on the sidewalls. It provides the tyre with flexibility and works with the casing to absorb shocks. The sidewalls also play a role in the lateral stability of the tyre.
Tread of radial tyre
The tread is then placed on the external surface of the tyre. This is a thick layer of rubber, moulded during the vulcanisation process to form lugs.
The main role of these lugs is to provide traction whatever the conditions in which the tyre is used. To achieve this, their shape, angle and position are optimised.
The lugs also stabilise the tractor during manoeuvres. The tread also contributes to the driver’s comfort.
The information contained in this publication is for guidance purpose only. Whilst every effort has been taken in its production, no responsibility can be accepted for any loss or damage arising from any kind of undetected technical or commercial error contained in this content. Any data supplied in this publication is subject to possible revision following the date of publication. Due to the constant advance of tyre technology, the contents of this publication are subject to change without notice.