Light Duty: Time For Tire Pressure Maintenance Systems

Since they come standard with all light-duty vehicles anyway, your fleet might as well start reaping the benefits.

Under-inflated tires have caused fleets more problems than your average B-movie gremlin—that is, until modern tire pressure systems and the recent motor vehicle standard hit the block. Could the feds actually be helping your shop’s bottom line?

Failure to properly maintain tires can set off a chain reaction of financial troubles for a fleet, including reduced fuel efficiency, handling, driving comfort and tire life as well as increased chances of accidents—more than 500 people are killed in the U.S. every year in accidents cause by tire defects, according to the National Highway Transportation Safety Administration (NHTSA).

Tire failures and fatal accidents were at the core of NHTSA’s regulation requiring all new 2008 model year passenger cars and light trucks to have a tire pressure monitoring system (TPMS) to alert drivers when the pressure in one or more tires falls 25 percent below the vehicle manufacturer’s recommended inflation pressure or a minimum activation pressure specified by NHTSA, whichever is higher.

This is the latest federal act in a series that started with the TREAD Act in 2000, enacted by Congress in response to reported tire failures caused by tread separation from certain Firestone tires installed on Ford SUVs and trucks that—according to NHTSA—resulted in about 268 fatal crashes from January 1991 to August 2001. In 2002 the administration mandated the systems on all new passenger cars and light trucks, but some consumer safety groups challenged the rule in court over concerns that certain systems would not sufficiently detect tire under-inflation. In response, NHTSA issued its new rule in 2005 that 20 percent of affected vehicles must have the systems for model year 2006, 70 percent for 2007 and 100 percent for the 2008 models.


Checking tire pressure should be one of the most basic maintenance rituals for fleets of any size, yet a Federal Motor Carrier Safety Administration (FMCSA) study showed less than half of the commercial vehicles were within five PSI of target pressure, and about 7 percent were under-inflated by 20 or more. As the saying goes, accidents on the street happen because of accidents in the shop, and tires are no different. Left untended, it is only a matter of time before tire materials are weakened to the point of failure—then it’s a matter of hoping your driver can keep their load on the road and get out of harm’s way without causing an accident. TPMS can give your drivers—and yourself—a little extra warning that can go a long way.

Though there are traditionally two kinds of systems—direct and indirect—most available commercially today are direct. These use pressure sensors in each wheel that tie into an on-board computer that warns drivers when any tires drop below 25 percent of the recommended level. Most OEM and aftermarket systems attach their sensors to special tire valves. These can detect gradual changes over time and in some cases provide a dashboard display to observe pressure readings.

Indirect systems warn drivers when a tire has lost at least 25 percent of recommended inflation compared to the other three, using ABS wheel speed sensors to measure differences in tire revolutions. These systems cannot warn drivers which tire is going flat, or if all four tires are losing pressure at a similar rate.

TPMS are relatively easy to install and maintain, since many vehicles already have wheel speed sensors for ABS or electronic stability control systems. There is some variety, as OEMs do have some options on how to fit these systems within NHTSA’s regulations. FMCSA’s stance on the systems was to “strongly suggest that the savings potential from tire pressure monitoring and automatic inflation systems could support the purchase prices of systems and products currently in the marketplace. The challenge for the supplier community is to prove reliability and reduce or eliminate added maintenance for the systems themselves.”


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