how do our cars know when the tire pressure is low? i just changed wheels and noticed the valve stems did not have pressure sensors.

 

They are band mounted to the rim TPMS sensors.

 

cool thanks are they easy to swap over, i never took the tire all the way of the stock wheels so i didnt see it. i havent gotten a error code without them, should I?

 

If you have the message center you should get some sort of message.
You then need to reset it every time you start the Stang.
If you dont have the message center then the TPMS Icon will illuminate
and flash for 70 seconds then go out until you start the Stang again.
Sometimes it comes on during long extended drive.
Its all explained HERE.

 

the 05's didn't come with the tire pressure monitoring system (which I'm glad about, because I don't have to hassle with the sensors or the bands).

I have to rely on the good 'ol tire pressure guage that has been around for many years...LOL!!

 

The 06 S197s didnt have TPMS either.

 

YAY for no TPMS! lol I prefer the "ol tire pressure gauge" anyways

 

I love not having one i just hate my oil pressure gauge (its pointing in the opposite direction)