Automatic tire inflator keeps pressure constant

The Aperia Technologies Halo Tire Inflator simply bolts to the wheel hubs of the drivers. They are not available for steer tires. Each unit is self contained and used a pendulum like mechanism to pump air into the standard valve stems. Aperia sells them for $299 each, and says they have sold thousands since introducing them in 2014. According to Aperia, the units have an expected maintenance-free life of over 500,000 miles or about 10 years.