Tires like most things in life are not invincible. They are made of individual layers of fabric and steel encased in rubber. If a tire is allowed to run on low air pressure, the rubber is forced to stretch beyond the elastic limits of the fabric and steel reinforcing cords. When this happens, the bond between the various materials can weaken. If this is allowed to continue, it will eventually break the bonds between the various materials and cause the tire to fail. And even if the tire doesn't fail immediately, once a tire is weakened it won't heal after being re-inflated to the proper pressure. So if a tire has been allowed to run nearly flat for a period of time, the tire is going to need to be replaced. Costing you in some cases hundreds of dollars.

Try flexing a piece of sheet metal back and forth and you may get to 30 or 40 times before it fractures.. Somewhat like that piece of sheet metal, your tire, when run low on air can rip at the weakest point. A typical 18 inch tire may revolve 750-800 times per mile! On a 20 minute trip at highway speeds the underinflated tire may needlessly over flex as many as 16 thousand times. 
We all know how quickly or slowly a tire can lose pressure, that phantom flat tire every 3 days sound familiar to you? Obviously air is getting out somehow.

 

TPMS or Tire Pressure Monitoring systems, continuously monitor the air pressure inside the tire. Some systems indicate which tire is low and may even monitor your spare, while others only alert you that one of your tire is low. Each wheel has a small sensor that is part of the wheels valve stem. The sensor is affixed to the inside of the wheel attached by the valve stem, inside the tire and wheel assembly. 

Each of your sensors is a small radio transmitter. It lays dormant (park mode) when the car is at rest. The sensor then wakes up when the car travels at 15mph. If the car comes to rest for 20 minutes or more the sensors shut down again to park mode. This extends the life the batteries, which should last between 7-10 years.

If the pressure exceeds the high or low limits of the pressure threshold, the sensor sends a signal to the system receiver and your warning indicator illuminates. ( ! ) You may have seen this on your dash and wondered what the heck it was. All vehicles produced after 2007 are mandated to be equipped with TPMS systems.  

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