Tire Pressure Monitoring

The National Highway Traffic Safety Administration checked nearly 12,000 vehicles in 2001
and found that about 27% had at least one tire under-inflated by 25% or more. As a result,
since Sept. 1, 2007, tire-pressure monitoring systems (TPMS) have been mandatory for every
new vehicle sold in the U.S. The regulation requires onboard monitors to warn drivers when
the air pressure in one or more tires is at least 25% below the auto maker’s recommended
cold-inflation pressure. Drivers still should maintain air pressure for the safety of the
vehicle, as TPMS units typically only warn when tires are seriously underinflated. Drivers
can typically find inflation information on the driver’s side door jamb, in the glove box
or underneath the lid of the center console. Most TPMS use sensors at the base of the valve
stem or on the wheel. They signal the driver via a radio transmitter when low pressure is
detected. Tire technicians using improper tools to remove old tires can damage the TPM
sensor, leaving it inactive when new tires are installed. Although the Tire Industry
Association reports that all major retailers have systems in place to ensure TPMS are
functioning after tires are serviced, consumers should tell tire technicians they have a
system and to check its operation afterward. Some vehicles have five sensors; one for each
wheel, plus the spare. Tires naturally lose about 1 psi per month. If consumers do not keep
their tires properly inflated, including the spare, eventually the warning light on the
dashboard will trigger.