The Technology Behind Auto-Inflating Tires

Auto-inflating tires are sexy on James Bond’s Aston Martin, but the technology is still ripe and not readily available outside of military vehicles, commercial trucks, and hummers. These tires have not found their way on to the majority of passenger cars, but major tire manufacturers such as Goodyear are steadily making progress researching this technology.

Why would anyone care?
Other than the luxury of not having to get down and dirty, checking and adjusting tire pressure, the technology is economical. According to Goodyear, underinflated tires reduce gas mileage by up to 15 percent for every 20 percent that they are underinflated. Furthermore, reduced tire pressure increases the likelihood of a rupture which could potentially cause an accident.

Central Tire Inflation System
The Central Tire Inflation System (CTIS) system is used by hummers and is the only system available to passenger vehicles. CTIS improves vehicle performance on various surface types by providing direct control over air pressure in each tire. For example, lowering tire pressure enhances traction on softer terrain by creating a larger area of contact. In addition, CTIS maintains steady pressure even during leaks caused by puncture.

Every wheel in the CTIS uses a valve to inflate or deflate tires at will and to extend the life of the tire by letting pressure off of the seal when it's not being used. An electronic control unit overlooks the entire system and monitors pressure at 10-minute intervals to maintain the desired amount. Commands are issued from the ECU to a pneumatic control unit which oversees the actual air and valve system. A dashboard GUI display allows drivers to select pressure settings and monitor the overall system. The same compressor supplying air to the brakes also supplies air to the CTIS, although a pressure switch ensures priority is given to the brakes.

A speed sensor is used in conjunction with CTIS to modify velocity based on the consistency of the particular speed. This is especially useful on the highway where higher pressure reduces the likelihood of damage.

Tire Intelligent Pressure Management
Similar to CTIS, Tire Intelligent Pressure Management (TIPM) uses compressors to automatically adjust the pressure in each tire while the vehicle is motion. Using a central receiver attached to the rim and four non-battery-operated modules, the inflation and temperature in each tired is measured and then transmitted wirelessly to the receiver. The system is digital and relies on an electronic brake system to determine the position of each tire.

Goodyear has been researching the technology since 2011, and began testing it commercially in 2012. As of yet, it is not available

Air Maintenance Technology
Goodyear's inflating tires offer a much simpler solution independent of valves, tubing, and pumps. On a basic level, the interior of the tire houses a sensor that detects pressure levels. Once these levels drop below a certain point, a side valve is opened, absorbing air into a tube build along the tire's circumference. Next, the vehicle's weight compresses this tube to inject air into the tire; thereby raising pressure levels.

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Story via Howstuffworks