philmcneal
04-09-2006, 09:31 PM
HyView
Email Author: Michael Millikin of Green Car Congress
Source: http://hybridcars.com/blogs/hyview/tire-labels
Two divisions of the National Academies—the Transportation Research Board and the Board on Energy and Environmental Systems—have issued a special report examining the contribution of tires to vehicle fuel consumption.
Tires and Passenger Vehicle Fuel Economy concludes that (1) reducing the average rolling resistance of replacement tires by a magnitude of 10% is technically and economically feasible and (2) such a reduction promises a 1% to 2% increase in fuel economy—representing between 1 to 2 billion gallons of fuel saved annually.
In conventional passenger vehicles, about 66% of the original fuel energy is lost through waste heat. In the city, only about 13% of the original fuel energy ultimately is transmitted to turn the wheels. On the highway, because the engine operates more efficiently, about 20% ends up in the wheels. The rolling resistance of the tires consumes about 33% of that mechanical energy output.
Although rolling resistance directly consumes only a small portion of the total energy expended by the vehicle (between 4% to 7%), reducing rolling resistance translates into a larger reduction in total fuel consumption because less fuel energy will need to be sent to the engine in the first place.
The main source of rolling resistance in on-road driving is the repeated flexing (deforming and recovery) of the tires as they roll. Through an effect known as hysteresis, this repeated flexing causes mechanical energy to be converted to heat. In turn, this requires the application of more mechanical energy from the engine to replace the energy lost as heat from hysteresis.
The design, construction, and materials of tires, as well as their maintenance (especially proper inflation), their condition, and operating conditions—although not an increase or decrease in travel speed—affect the rate of energy loss.
Each year, Americans purchase about 200 million replacement tires for their vehicles—a $20 billion market. Although the fuel savings obtained by opting for a lower rolling-resistance tire may not make an enormous amount of financial difference to a single buyer (perhaps around $36 a year with gas at $3/gallon), the collective reduction in consumption could be quite significant—1 to 2 billion gallons the report highlights.
But even if consumers wanted to choose lower rolling-resistance tires, it’s very difficult to find the necessary information.
As the report notes, “A significant and sustained reduction in rolling resistance is difficult to imagine under any circumstances without informed and interested consumers. The committee observes that consumers now have little, if any, practical way of assessing how tire choices can affect vehicle economy.”
As a result, the report calls on Congress to direct the National Highway Transportation Safety Administration and the EPA to work together on gathering the rolling-resistance data and developing a way to convey it in a timely and easily understood manner by both buyers and sellers.
Adding RRC labeling to tires would be a good way to start.
And then it’s up to consumers to make rolling resistance and fuel economy as much a consideration in a tire purchase as traction and handling.
Email Author: Michael Millikin of Green Car Congress
Source: http://hybridcars.com/blogs/hyview/tire-labels
Two divisions of the National Academies—the Transportation Research Board and the Board on Energy and Environmental Systems—have issued a special report examining the contribution of tires to vehicle fuel consumption.
Tires and Passenger Vehicle Fuel Economy concludes that (1) reducing the average rolling resistance of replacement tires by a magnitude of 10% is technically and economically feasible and (2) such a reduction promises a 1% to 2% increase in fuel economy—representing between 1 to 2 billion gallons of fuel saved annually.
In conventional passenger vehicles, about 66% of the original fuel energy is lost through waste heat. In the city, only about 13% of the original fuel energy ultimately is transmitted to turn the wheels. On the highway, because the engine operates more efficiently, about 20% ends up in the wheels. The rolling resistance of the tires consumes about 33% of that mechanical energy output.
Although rolling resistance directly consumes only a small portion of the total energy expended by the vehicle (between 4% to 7%), reducing rolling resistance translates into a larger reduction in total fuel consumption because less fuel energy will need to be sent to the engine in the first place.
The main source of rolling resistance in on-road driving is the repeated flexing (deforming and recovery) of the tires as they roll. Through an effect known as hysteresis, this repeated flexing causes mechanical energy to be converted to heat. In turn, this requires the application of more mechanical energy from the engine to replace the energy lost as heat from hysteresis.
The design, construction, and materials of tires, as well as their maintenance (especially proper inflation), their condition, and operating conditions—although not an increase or decrease in travel speed—affect the rate of energy loss.
Each year, Americans purchase about 200 million replacement tires for their vehicles—a $20 billion market. Although the fuel savings obtained by opting for a lower rolling-resistance tire may not make an enormous amount of financial difference to a single buyer (perhaps around $36 a year with gas at $3/gallon), the collective reduction in consumption could be quite significant—1 to 2 billion gallons the report highlights.
But even if consumers wanted to choose lower rolling-resistance tires, it’s very difficult to find the necessary information.
As the report notes, “A significant and sustained reduction in rolling resistance is difficult to imagine under any circumstances without informed and interested consumers. The committee observes that consumers now have little, if any, practical way of assessing how tire choices can affect vehicle economy.”
As a result, the report calls on Congress to direct the National Highway Transportation Safety Administration and the EPA to work together on gathering the rolling-resistance data and developing a way to convey it in a timely and easily understood manner by both buyers and sellers.
Adding RRC labeling to tires would be a good way to start.
And then it’s up to consumers to make rolling resistance and fuel economy as much a consideration in a tire purchase as traction and handling.