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Understanding a tire pressure monitoring system

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Posted: Monday, November 22nd 2010

TPMS sensor on rimIt’s no secret that properly inflated tires provide maximum gas mileage, allow for more even tire wear, and extend the life of the tires.  TireSafety.com offers insight into the negative impact underinflated tires can have: “Under inflation is the leading cause of tire failure. A tire can be as much as 50% under inflated before it is visibly noticeable.  Not only are under inflated tires more prone to damage and failure, but they can lead to higher fuel costs by as much as 3 to 5¢ per gallon.”

It’s important to note that cold weather reduces tire pressure; many people are unaware of this. A general rule is that every ten degree drop in temperature creates a one pound drop in tire PSI.

The gradual loss of air, as the result of temperature decreases or poor maintenance is the primary cause of tire blowouts – and the cause of many traffic accidents and fatalities. Tire Pressure Monitoring Systems, or TPMS, was specifically developed to deal with this problem.

Following the Firestone tire crisis, which in the late 1990’s was attributed to more than 100 deaths from rollover accidents due to tire tread-separation, the Clinton administration published the TREAD act. This act mandated the use of a suitable TPM technology in order to alert drivers of a severe under-inflation condition of their tires. This act affects all light motor vehicles (under 10,000 pounds) sold after September 1, 2007.

Phase-in started in October 2005 at 20%, and reached 100% for vehicles produced after September 2007.

Tire pressure monitoring systems vary depending on the make and model of the vehicle; they may be mounted differently from one vehicle to another and they may utilize different methods of letting the driver know the pressure is low.  Typically a TPMS sensor is connected to the valve stem on each wheel of the vehicle.  Each sensor constantly monitors the current tire inflation based on both temperature and wheel speed, and transmits this information to the vehicles onboard computer.  If the inflation pressure falls below a safe level, TPMS alerts the driver by means of a signal lamp on the dashboard instrument panel.  Some tire pressure monitoring systems provide detailed information about the pressure in each individual tire while others provide basic information that one of the tires has low pressure.

By continuously taking accurate measurements, monitoring tire inflation pressure, and informing the driver when under inflation is detected, TPMS dramatically improves driving safety. It also reduces automobile accidents and fatalities, maintains your car’s performance level, increases fuel efficiency, and extends tread life.

TPMS dashboard iconHowever, in a blog post titled Survey results not so surprising about TPMS, Lori L. Mavrigian noted that survey results show that many people are not able to take advantage of the benefits of a tire pressure monitoring system because they do not really know what it is.  Mavrigian’s post cited a survey by Schrader International, noting that “46% of drivers couldn’t figure out what the tire pressure monitoring system … on their dashboard really was.”  She went on to note that the survey “found a third of survey respondents didn’t know what a tire pressure monitoring system even is, and 14% thought the warning light was for something else altogether!”  The survey found a gender divide, as well as an age divide, in the results.  Specifically, male drivers were more likely to know whether the car was equipped with a monitoring system and the meaning of a TPMS alert than female drivers.  In terms of age, “Younger drivers are significantly less likely than their older counterparts to correctly identify the tire pressure warning alert icon (Gen Y (18 to 29), 29%; Gen X (30 to 45), 46%; Baby Boomers (46 to 60), 62%; Silent Generation (60+), 64%).

While we can’t validate the results of this poll, it does shed some interesting light on the general awareness of TPMS.  If a large percentage of people really are not knowledgeable about TPMS, perhaps a general campaign is necessary.  For a TPMS to have maximum benefit, drivers need to recognize and understand how it works and when to take appropriate action.  This is important since automobile manufacturers are now required (as of 2007) to include TPMS in vehicles (Transportation Recall Enhancement Accountability and Documentation (TREAD) Act).

As drivers have done for over a century, it is still possible to check tire pressure manually.  The appropriate inflation level will vary; it is best to consult vehicle and tire specifications or ask a Dunn Tire expert for advice.  The Rubber Manufacturers Association (RMA) reminds drivers to check the pressure when the tires are cool, “meaning they are not hot from driving even a mile.”  The RMA recommends checking tire pressure on a monthly basis, as well as before going on a trip, and advises motorists to check the pressure in the spare.  Tire pressure monitoring systems remove most of that burden from the driver and provide the driver with peace of mind that the tire pressure is at the appropriate level.