Low Rolling Resistance Tires
What is rolling resistance and how can it help reduce a vehicle’s fuel consumption?
Conventional tires lose energy through internal friction as they roll down the road. As the wheels turn to move the vehicle forward, the tires change their shape in order to make and maintain contact with the road. The section where the tire meets the road is called the contact patch.
All of the forces needed for acceleration, braking and cornering are transmitted through this contact patch. It is the ability of the tires to adapt their shape (deform) that ensures proper grip and comfort (smooth versus bumpy ride). The rubber compounds in a tire give off energy in the form of heat when they are deforming—if you have ever touched a tire after it has been running for some time, you will realize just how much heat is generated and how much energy is wasted. The amount of energy required by the tire to deform is called rolling resistance. Tires that have a low rolling resistance require less energy to deform into the contact patch. Reduced energy loss through the use of low rolling resistance tires translates into reduced fuel consumption and emissions.
Did You Know?
Several factors can help reduce the environmental impacts of tires.
- Tire Pressure – Tires designed to operate at higher pressures reduce the deformation of the tire.
- Rubber Compounds – Harder and lighter compounds do not deform as much, thus requiring less energy.
- Dimensions – Narrow, low profile tires generally require less energy to deform.
- Weight – Tires with less material require less energy to deform and reduce the unsprung weight of the vehicle.
- Tread Pattern – Smooth tread patterns roll more easily than coarse tread patterns. Short lugs and narrow gaps improve rolling resistance.
- Compounding Methods – Using alternatives to toxic oils during fabrication helps reduce environmental impacts.
eTV Study on Low Rolling Resistance Tires
All tires have a rolling resistance coefficient—a parameter that defines how much resistance a tire encounters as it deforms into the contact patch—both at a static state when the vehicle speed is kept constant, and in a dynamic state when the vehicle’s speed is changing (such as when accelerating or slowing down). Generally, a tire with a higher rolling resistance coefficient will cause a vehicle to burn more fuel to keep the vehicle moving, and thus cause a vehicle to have higher fuel consumption. And by consuming more fuel, the tailpipe emissions (GHGs and other pollutants) also increase.
The eTV program is undertaking a study on a number of different tires mounted on 15- and 16-inch rims, the most common tire sizes in Canada, to:
- quantify the extra time a vehicle is able to coastdown for a predetermined reduction in rolling resistance;
- assess whether reducing the rolling resistance has an impact on dry braking distances;
- evaluate the extent to which rolling resistance can affect fuel consumption.
- determine whether rolling resistance coefficients can be used to compare the environmental benefits of tires;
This study will allow Canadians to learn more about the benefits of lower rolling resistance tires and their contribution to reducing fuel consumption and emissions.
eTV preliminary test results
National Academy of Sciences, 2006
Low Rolling Resistance Tires Test Plan – Alternative Format – Adobe PDF
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The following vehicles in the eTV fleet are equipped with low rolling resistance tires: