New and innovative technologies can help improve fuel efficiency and reduce greenhouse gas (GHG) emissions for light-duty vehicles. Alternative fuels, electric batteries, hydrogen electric fuel cells, hybrid technologies and improved power trains, emissions controls and aerodynamics all have the capacity to reduce vehicle emissions on Canadian roads. However, the use of low rolling resistance (LRR) tires as replacement tires can also help to reduce fuel consumption in vehicles.
The reality is that it takes energy to get a vehicle down the road. Part of that energy is used to overcome air resistance (drag), friction resistance (e.g. internal friction such as in the transmission) and rolling resistance. Once a vehicle has been manufactured, a driver can do little to reduce the air or friction resistance. But a driver may be able to do something to minimize rolling resistance.
On average, more than 80% of a vehicle’s fuel energy is lost through various thermal, frictional and standby losses.2 However, low rolling resistance tires can help reduce this loss of energy by making vehicles more efficient as they drive down the road. In fact, recent studies performed by manufacturers, as well as third party evaluations, have found that low rolling resistance tires can help reduce a vehicle’s fuel consumption by as much as 4.5%.
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.
Several factors can help reduce the environmental impacts of 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:
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.
1 eTV preliminary test results
2 National Academy of Sciences, 2006
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The following vehicles in the eTV fleet are equipped with low rolling resistance tires: