Don’t TREAD On Me: Tire Pressure Monitor Systems

September 15, 2013 | Reply More

In 2000, the U.S. government responded to serious issues related to automobile tire safety with the TREAD (Transportation Recall Enhancement Accountability and Documentation) Act. This mandated that an elaborate computer-controlled system had to be added to every passenger vehicle to monitor tire pressures. It’s our job to keep these systems up and running.

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Some of you may remember the stories of tread separation and tire failure in the late 1990s and the fatalities that occurred. The National Highway Traffic Safety Administration (NHTSA) monitors trends like this, and after compiling accident report data it started to look for a cause. Numerous factors were discussed such as properly matching tire construction to vehicle design, recall oversight, and, above all, tire maintenance. It was concluded improper tire pressure was the most common cause of catastrophic failure.

As a technician, you are probably instructed to check the tire pressure at every oil change you do in the shop. In an ideal world, tire pressure should be checked at least once every two weeks. But the driving public is not known for diligence in this matter, and we do not get to see their vehicles every two weeks. We should inform our customers that a properly inflated tire will not only provide better traction under various road conditions (rain, snow, road surface temperature, etc.), they will also last thousands of miles longer and provide the best fuel economy the vehicle can offer. This advice could save them a lot of money in the long run, but it mostly goes unheeded. With the mileage the driving public increasing every year, something had to be done in the name of tire safety.

What was done?

In 2000, the federal government stepped in and mandated that all manufacturers that sell vehicles in the United States would have to install a Tire Pressure Monitoring System (TPMS) on every new vehicle. This was only one of the stipulations of the mandate, but it is the one we as automotive technicians need to be most concerned with. After all, it is our job to make sure that these warning systems continue to operate as designed.

When trying to determine if you're working with an indirect or direct system, look for the lock nut holding the sensor to the rim. This means it is a direct system. Use only plastic valve caps because galvanic action will corrode the metal type on the valve stem making them difficult to remove.

When trying to determine if you’re working with an indirect or direct system, look for the lock nut holding the sensor to the rim. This means it is a direct system. Use only plastic valve caps because galvanic action will corrode the metal type on the valve stem making them difficult to remove.

TPMS has evolved as more information was learned about the effects of improperly inflated tires. What makes an unsafe level of tire inflation? Radials have steel or fiber cords running across and in-line with rotation. If the air pressure drops, the sidewall of the tire must support more of the weight of the vehicle. As a tire rotates, the sidewall compresses directly above the point of ground contact. The tire then expands again as the tire continues to rotate. This sidewall flexing results in heat build up. Heat is also generated by

 

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Category: the bimmer pub, Tires + Wheels + Hubs + Bearings

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