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"  Searching for the air hose in the grimiest corner of a neighborhood service station may soon become a thing of the past. With the help of a $1.5 million Department of Energy grant, Goodyear is developing a tire that regulates its own air pressure. Though the company refused to leak details of how the system works, a 2009 patent application shows that the tire employs a pressurized internal tube with inlet and outlet valves. This differs from the automatic inflation system on military vehicles that use onboard compressors. &amp;quot;The Air Maintenance Technology system is powered by the tire itself as it rolls down the road,&amp;quot; says Goodyear chief technical officer Jean-Claude Kihn. Underinflation can lead to tire failure and a possible crash, but in most cases it just wastes fuel. According to Goodyear, underinflation cuts a car&amp;#039;s efficiency by 2.5 to 3.3 percent, which, at current fuel prices, effectively adds more than 10 cents per gallon. 1. Intake Air entering the inlet fills a small, high-pressure tube encircling the rim. 2. Big Push Air is forced through the inner tube by ground pressure on a low tire. 3. Inflate Tire pressure returns to normal as air fills it through the outlet valve. 4. Vent Excess air escapes through the inlet port. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.popularmechanics.com/cars/a7342/how-it-works-self-inflating-tire/>