Advice
Safety advice

Functions of the tyre

Related risks

Carry the load Defined by the vehicle characteristics:axle load An under-sized tyre under load will overheat. This may lead to rapid deterioration of the tyre on the road which may even go so far as a sudden loss of inflation pressure. The tyre footprint will not be optimised, which can affect handling and grip: steering, traction and braking maybe
affected. Retreading may be compromised. Service life will be reduced.
 Ability to carry the load at maximum speed Defined by the vehicle characteristics: maximum speed of the vehicle An under-sized tyre travelling at speed will overheat. This may lead to rapid deterioration of the tyre on the road which can result in a sudden loss of inflation pressure. Retreading may becompromised. Service life will be reduced.
Travel on different road surfaces According to the conditions of use A tyre which is not suitable for the position or use may:
- overheat: as in the case of an urban tyre used on long       motorway journeys.
- deteriorate: as with the tread of a long distance tyre          which is used on unsurfaced roads.
In the latter case, a tyre showing deep-seated damage must be examined by a specialist to determine whether it can continue in use, can be repaired or needs to be withdrawn from service. Note that if the reinforcing plies are exposed they will deteriorate: a tyre with this kind of damage is considered unfit for use under the terms of the Construction and Use Regulations (1986). This damage may lead to rapid deterioration of the tyre on the road and can result in sudden total deflation. Retreading may be compromised. Service life will be reduced.
Steer the vehicle According to the conditions of use by providing feedback to the driver about the conditions of use On the Steering axle, fitting a tyre which is not suitable for the position or use may result in less precise steering, depending on the state of the road surface and the speed. This may prejudice complete control of the vehicle.
Steer the vehicle Special feature of front axle: specially adapted tread pattern and uniformity The tyres on the Steering axle are the first ones in contact with the road surface ahead. Tyres designed for this axle must give a steady feedback of information on changes in the condition of the road surface, such as a fleeting reduction in grip, for example. A tyre not designed for this
axle may be less progressive or filter out certain information on changes in the road surface.
Provide a comfortable ride Special feature of front axle tyres: specially designed
tread and uniformity
The Steering axle is particularly sensitive to tyre uniformity: link with the steering wheel, position near the driver, etc. Tyres intended for this axle are specially designed to meet this criterion and also have tread patterns adapted to optimise this function. A tyre not designed for the Steering
axle will have a poorer response to this function.
Transmit braking forces Braking: related to the vehicle's braking system.
The front axle is put under considerable strain during emergency braking.
Braking with a retarder is carried out by the drive axle.
Under emergency braking, a major transfer of load is exerted on the Steering axle: the tyres on this axle therefore have a crucial role to play in the vehicle’s stopping distance. The braking performance of a tyre not designed for the Steering axle may not be as good when
it is fitted in this position.
When braking with retarder systems, the tread and casing of Drive axle tyres are very much brought into play: an unsuitable tyre will be less effective in transmitting the torque and service life will also be reduced.
Transmission
of torque
Torque: depends on the power and the torque of the vehicle Vehicle acceleration is provided by the tyres on the Drive axle only: an unsuitable tyre will be less effective in transmitting torque and it's service life will be reduced.
Long life for optimised business efficiency In relation to mileage performance The tyres must be suited to the axle and the use of the vehicle: a tread pattern not suited to the axle or a range unsuitable for the use will not give the mileage performance corresponding to the tyre’s potential.
Long life for optimised business efficiency In relation to the vehicle's
fuel consumption
The tyres on a commercial vehicle have a major impact on the vehicle’s fuel consumption. The choice of range and tread pattern will have an effect on fuel consumption. For some uses, it is possible to optimise consumption by using tyres with low rolling resistance.
The rolling resistance of tyres reduces as the tyres become worn: replacing a tyre before it is completely worn* results in a loss of potential fuel savings.

*Refer to a country's local legislation for their definition of minimum permissible tread depth.