Jun 18 2009

California On a Roll

Posted by: Jonathan Marshall

Last summer, a presidential candidate named Barack Obama drew hoots and hollers from opponents for claiming that properly inflating your tires is a simple but important step individuals can take to save energy.

For all the derision he endured, Obama was right, of course. Tire pressure and road friction significantly affect auto fuel economy. The Department of Energy reports that "a vehicle with a recommended pressure of 35 psi whose tires are at 28 psi will have increased its rolling resistance by 12.5%."

Ironically, Obama was echoing an advertising campaign mounted by the first Bush administration in 1990, called "Do Your Part, Drive Smart," which advised that drivers collectively could save millions of barrels of oil a year simply by increasing the air pressure in their tires.

California has long understood the importance of tire friction. In 2003, the state passed a law that required the development of reporting requirements from manufacturers to help consumers compare the fuel economy of different tires.

A 10 percent improvement in the rolling resistance of older tires used in California could reduce the state's consumption of oil by more than 250 million gallons (saving about $750 million) and reduce CO2 emissions by 2.7 million metric tons annually, according to the California Energy Commission.

California's Air Resources Board already requires service stations to check tire pressure whenever they do repairs. Last week, the California Energy Commission proposed a new rating system for tires sold in California based on their rolling resistance, according to my favorite bedtime periodical, Modern Tire Dealer.

The Commission proposes to award the label "fuel efficient tire" to all tires that fall within 15 percent of the lowest measured "rolling resistance force." It would be like an Energy Star label for tires.

The Commission believes such ratings will "ignite a competitive spirit" among tire manufacturers to win the coveted label. But the Rubber Manufacturers Association advocates less costly testing requirements and a "self-certification" system for ratings.

Until the new ratings are final and published, one good source of information is Consumer Reports, which claims to be "the only independent group that rates tires for both performance and rolling resistance." Wikipedia also has a good list of tires with low rolling resistance.

Consumer Reports, which was invited by the Commission to be part of its rating proposal process, has this caveat:

Rolling resistance should not be the primary reason for a tire purchase. The most important considerations are safety-related performance features including dry- and wet-braking, hydroplaning resistance, handling, winter traction if applicable in your region, and tread-life. Low rolling resistance should be a secondary consideration in your tire-buying decision.

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