As a vehicle travels down a road, there are a number of factors that contribute to the amount of fuel it will use in getting from Point A to Point B. Tires are just one of those many factors.
As each tire on a vehicle rolls down the road, it creates a drag force. It is composed of the energy loss created by the deflection of the tire sidewall and the compression and deformation of the tire tread in the footprint at the road surface. This drag force is called rolling resistance and can be measured very accurately in a laboratory.
The contribution of tires 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 traveling 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. Tire rolling resistance increases with speed, but tires are a proportionally smaller percentage of the total drag on a vehicle as the speed increases.
A heavily loaded truck will use more fuel than a lightly loaded truck. Think of the extra fuel you might use when taking the entire family (and luggage) on vacation compared to the fuel you might use in the same vehicle with you as the driver and no passengers. For a truck, a good rule-of-thumb is that for each 10,000-lb. increase in load, fuel economy will drop 5 percent.
Wheel Alignment And Inflation Pressure
If any of the wheels on an 18-wheel tractor and trailer are not properly aligned, the total drag on the vehicle increases. There is greater “scrub” of the tires against the road surface and, potentially, greater aerodynamic drag when the tractor and trailer are not tracking parallel to the direction of travel.
The driving habits or “style” of the operator of a vehicle can have a very large influence on the amount of fuel consumed. Aggressive drivers can negate many of the gains obtained from investments in fuel-efficient tires and engines, aerodynamic devices or synthetic lubricants. With today’s technology, it is possible to accurately measure the amount of fuel an engine uses over a period of time so programs can be set up to reward drivers for fuel efficiency.
Ambient air temperature, weather conditions, road surfaces (gravel, asphalt, concrete) and terrain (flat, hilly, mountainous) are “environmental” factors that are impossible to control, but have a direct effect on fuel consumption.
Back To Tires
Each of the wheel positions contributes a portion to the total tire rolling resistance. Since the drive and trailer tires account for over 85 percent of total rolling resistance, tire companies concentrate their fuel efficiency efforts on these axle positions.
Source: Goodyear Commercial Tire Systems
- Most of the gains in fuel efficiency can be obtained from the tread of the tire, from the tread compound, tread design and/or the tread depth. Research shows that the tread contributes to over half of the rolling resistance.
- It is important to keep tires properly inflated so that the strength of the tire is not compromised. Fuel economy falls off sharply when tires are underinflated.
- If a rolling resistance improvement is made with the tread only, the improvement diminishes as the tread is worn down to zero tread depth.
- If a rolling resistance improvement is made in the casing components of the tire, that improvement will remain throughout the tread life of the tire.