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Tire Pressure Monitoring System

Updated on March 24, 2010

The Tire Pressure Monitoring System (T.P.M.S.) is the result of the Transportation Recall Enhancement, Accountability and Documentation (Tread) Act that was signed into law on November 1, 2000 by President Clinton. The Tread Act was published by the Clinton Administration following the Firestone tire recall in the late 1990's. The recall began when tire separation caused rollovers resulting in over 100 deaths. As a result of the Tread Act, it is mandatory that these systems be installed on all cars manufactured in the United Stated after September 2007.

Tire Pressure Monitoring System

System Design

The TPMS is designed to monitor the pressure of the tires and notify the driver if one should become excessively low. This is done in one of two ways depending on the type of system used. First is the indirect system, which monitors the rotation of the wheels. A tire with lower air pressure will have a smaller diameter, therefore it will have a higher rotation. When one wheel's rotation becomes higher than the others, a warning light will be activated by the system. The second is the direct system, which monitors the physical pressure inside each tire. When one tire pressure drops significantly more than the other tires, the system will activate a warning light inside the automobile notifying the driver of a potential problem.

Low Tire Alert

Driver Responsibility

The TPMS is designed to inform drivers of an excessively low tire, a tire that is significantly lower than the others. Tires will lose approximately 3 to 5 pounds per square inch (psi) of pressure per month. The direct sensor will not activate the warning light in this case because all tires have relatively the same pressure, and the indirect sensor will not detect this because the rotation will remain the same in relation to the other tires. This is why it is best to have the tire pressure checked on a regular basis.

Once the warning light has been activated, it is the driver's responsibility to have the tires checked. If one tire should become excessively lower than the others it should be taken to a repair shop to be examined for a possible leak. Driving on a excessively low tire can result in ruining the tire, or worse case scenario can cause an accident.

Low tire pressure?

Proper Tire Pressure

Depending on the size, quality, and manufacturer of the tire, the maximum recommended tire pressure for a 4-ply rated tire can range between 32 psi to 51 psi. The automobile manufacturer states the recommended tire pressure in the owner's manual, however, this pressure can be considerably lower that what is stated by the tire manufacturer. Most tire repair shops state that it is best to keep the pressure close to what is stated on the tire for better tire wear and gas mileage. Automobile manufacturers state for a smoother ride follow the recommended pressure stated in the owners manual. However, this may decrease the gas mileage of the automobile, as well as the life of the tire.

How can low tires affect the gas mileage? If anybody has tried to move something with low tires, they have noticed how hard it is to move. It takes more effort to get the object moving, as well as keep it moving. An automobile's engine requires more gas to provide this extra effort when tires are low. Properly inflated tires tend to roll easier, taking less effort, and using less gas for the engine to move the vehicle.

Excessive tire wear can be caused by improperly inflated tires. This can lead to replacing tires more often. The surface of the tire, or tread, should have a even wear pattern. A over-inflated tire will wear the center of the tread, while a under-inflated tire will wear the outside edges of the tread. Checking the wear pattern during regular service can determine if the tires are properly inflated.

Be Sure to Check Your Pressure

Tire Wear Chart

What's your thoughts on TPMS

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