COMMERCIAL VEHICLE TYRE DATA - types of tyre
Fuel Economy and Tyres - Factors Affecting Truck Fuel Economy
There are a number of factors that contribute to the amount of fuel a vehicle uses.
The main parameters are vehicle weight, aerodynamic drag, mechanical losses, driving style and rolling resistance. Although tyres are just one of these factors, they can affect up to 1/3 of the vehicle's total fuel consumption.
Each tyre creates drag. This is caused to a great extent by energy loss due to the deformation in the tyre as it travels over the road.
This drag is called rolling resistance.
The contribution of tyres to the total energy required to move a vehicle down the road is dependent upon the effects of many outside factors, which include:
Aerodynamics and Speed
A vehicle's aerodynamics and its travelling speed have an extremely large effect on how much fuel is consumed.
The force created by the aerodynamic drag of a vehicle goes up exponentially with the speed of the vehicle.
Tyre rolling resistance increases linearly with speed, but tyres are a proportionally smaller percentage of the total drag on a vehicle as the speed increases.
Ambient air temperature, weather conditions, road surfaces (sand, gravel, asphalt, concrete) and terrain (flat, hilly or mountainous) are environmental factors that are impossible to control but have a direct effect on fuel consumption.
On a typical 40 ton, 5 axle truck, each axle contributes to a portion of the total vehicle tyre rolling resistance.
Drive and trailer axles combined contribute about 83% of the total tyre rolling resistance. To minimise the vehicle's fuel consumption, it is recommended to equip all axles with low rolling resistance, fuel efficient tyres.
Tyre rolling resistance is heavily dependent on inflation pressure. A 1 bar deviation from the nominal inflation pressure could lead to a 5% difference in rolling resistance, which may result in a significant fuel cost increase (see example below).
For optimum rolling resistance, it's important to have the tyres inflated correctly, as recommended for the respective axle loads. In addition, under inflation may have negative effects on tyre durability and can cause failure.
1 bar under inflation in every tyre can cost £800 of fuel per year and the carcass can be lost for retreading.
Incorrect axle alignment drastically influences rolling resistance,increasing fuel consumption andcausing accelerated tyre wear.
If any axles on a truck are not properly aligned, drag increasesand the tyres wear out much faster.This means more fuel used and accelerated tyre wear.
The driving habits or style of the driver of a vehicle can have a very large influence on the amount of fuel consumed.
Aggressive driving can wipe out many of the gains obtained from investments in fuel-efficient tyres and engines, aerodynamic devices or synthetic lubricants.
With today's technology, it is possible to accurately measure the amount of fuel a vehicle uses over a period of timeallowing for programs to be set up to reward drivers for good fuel efficiency.
Fuel Efficient Truck Tyres
However, today's modern automated truck drivelines tend to reduce differences the drivers can have on fuel economy driving thus further increasing the saving potential of fuel efficient tyres.
Tyre Rolling Resistance
In addition to the recommended use of specific "fuel efficient" tyres, here are a few general comments concerning factors affecting tyre rolling resistance:
- Rib type tyres are better with regard to rolling resistance than block type tyres, this is mainly due to less movement of the tread in the contact patch area.
- Low aspect ratio tyres are stiffer, allowing for less flexing under load, thus they typically have lower rolling resistance compared to high aspect ratio tyres.
- Worn tyres have less rolling resistance than new tyres - as a truck tyre wears down, the tread pattern stiffens, which leads to less flexing/deformation in the tread area.
The use of fuel efficient tyres on all axle positions can make a significant difference in fuel consumption, a reduction of 10% of rolling resistance on a complete vehicle results in approximately 3% reduced fuel consumption (approx 0.9 litres/100 km on a vehicle which consumes 30 litres/100 km).
The importance of rolling resistance to a vehicle's fuel economy is show by the EU Tyre Label. From 1st November 2012 labelling information must be supplied with most heavy truck tyres sold in the European Union. This information is to help buyers make a more uniformed decision when purchasing tyres. The label covers ratings for fuel efficiency (rolling resistance), wet grip and exterior noise.
A high grading in fuel efficiency represents less rolling resistance and directly impacts on fuel consumption and the environment. With lower rolling resistance a tyre requires less energy so less fuel is used and, in turn less CO2is emitted. A win-win situation.
Effects may vary according to the vehicle and driving conditions. However, the difference between a complete set of new A-class and F-class tyres could reduce a truck's fuel consumption by up to 15%, which is equivalent to an annual saving of more than £6,000.
Using low rolling resistance, fuel efficient tyres in place of standard tyres, in combination with good vehicle and tyre maintenance and an economic driving style, minimises fuel consumption.
With today's fluctuating fuel prices, as well as more and more restrictive emission legislation, fuel consumption is a major economical factor in transport operations
Tyre choice and tyre maintenance account for a large part of these cost savings.