Radial tyres were developed in 1946 by Michelin. At the time there was a need for more flexible tyres which were able to absorb shocks generated by road surfaces. The sidewall of radial tyres and the tyre tread work as two independent features. The flexibility of a Radial tyre, together with its strength, are two combined factors which mean a radial tractor tyre absorbs impact shock and bumps more effectively than a cross-ply tyre.
The flexibility of the sidewall enhances vehicle stability and provides maximum contact of the tyre with the road surface. This, in turn, leads to a more comfortable ride and allows the driver to work longer. These tyres are also stronger, which means machines that use tyres like truck tyres or tractor tyres can be operated at higher load capacities.
In radial tyres, steel cord plies are placed on the heel of the tyre, and a belt is placed across the casing. Because cord plies are placed directly on top of each other, the sidewalls of radial tyres remain very flexible.
Advantages of radial tyres include:
- Good steering and better road contact
- Improved driving comfort thanks to flexible sidewalls
- Less heat generated in the tyre at high speeds
- Higher resistance against tread-related damage
- Lower fuel consumption through better tranfer of energy from machine to road
Disadvantages of radial tyres include:
- The soft sidewalls are vulnerable when, for example, vehicles collide with curbstones
- Minor bumps in road are dealt with less effectively because radial tyres feature a steel belt
Crossply tyres have been used instead of full rubber tyres since 1898. They were a standard feature in the car tyre industry before radial tyres were introduced.
Crossply tyres consist of carcass layers made from nylon cord. They are placed diagonally across each other in the tread and the sidewalls, at an angle of 55 degrees. Multiple rubber plies overlap each other and they form a thick layer, resulting in less flexibility which can make it more sensitive to overheating. Therefore all high speed Tractor tyres are of Radial construction.
Crossply tyres provide a strong and rigid sidewall which tries to follow the natural lines of the road and this can cause a tyre to overheat when it is used on a hard road surface and this in turn, causes the tyre to wear out more quickly. However, the sidewall of a crossply tyre is more rigid than that of a radial tyre so is more resilient at preventing sidewall damage. Crossply tyres are therefore sometimes used if sidewall damage is a problem.
The crown of a crossply tyre and the sidewall of the tyres are dependent on each other. The tyre does not come into as much contact with the ground as a radial tyre and this may lead to less engine power transmission or more site damage. As it does not absorb as much impact shock, the driver can feel more vibration.
The initial cost of Crossply tractor tyres is cheaper than Radial tractor tyres so they are often an attractive choice to anyone on a budget. The rigid ride a crossply tyre provides can also be a benefit in applications where any tyre bounce would be a problem, such as on telehandlers or forklift machinery, so the rigid sidewall can be an advantage in certain working environments.
Advantages of crossply tyres include:
- Improved vehicle stability
- Higher resistance against sidewall damages
- Cheaper to produce
Disadvantages of crossply tyres include:
- High rolling resistance, which causes tyres to quickly heat up
- Reduced comfort due to the tyre’s rigidity
- Increased fuel consumption