TPMS is Totally Different From PMS

Every fall as the air turns chill, a cute little light (with an exclamation point) comes on in my car.  This light is the tire pressure monitoring system (TPMS) and it lets you know when a tire is low on air.

The TPMS light is designed to look like a tire. 

Now why does this light come on every fall?  I mean, that's weird.  I haven't run over anything, my driving is the same, then why am I suddenly low on air?

As the temperature falls, air condenses, including the air in your tires, which leaves your tires a little low. All you need to do is bring your tire to the correct PSI (pounds per square inch) and after driving a few miles, the light will automatically go off.

Besides making the pesky little light go off, why does it matter what your tire pressure is?  The quick answer is that tires are expensive, so you want them to last as long a possible.  To get the slowest and most even wear, your tires need to be at the correct PSI.

There is also too much of a good thing.  It's not a matter of, if some is good more is better, when tires are over inflated you feel every bump and crack in the road.  Like under-inflation, your tires wear out more quickly because they wear out unevenly.  And, if it's over-inflated, you run the larger risk that your tire will pop if you hit something wrong.  (I once watched a driver in a small sudan pop a tire in a parking lot when he hit the curb--something we affectionally call "a curb check.")

To find the correct PSI, the best place to check is your owner's manual.  The tire itself has a maximum PSI listed, but the reality is, that you don't want your tires at the maximum PSI it can handle. Plus, let's be honest, it's really, really hard to find words on your tires that are the same color as your tires.  In order to see it, you need to be in direct sunlight, hold your hand to the level of your eye, say some magic words and do seven squats.  Then, if you're really lucky, you might be able to make out some of what the tire says.   Your owner's manual is quicker, easier and more accurate.

After going through the aforementioned tire reading ritual, my husband said that my tires say that the max PSI is 40.  (I never could see it, but I'm taking his word for it.)  My owner's manual, however, recommended that the front tire PSI be 33 and the rear tires 35 PSI.  For driving comfort, this is an important difference.

This is where I make a confession.  I am a 36-year-old mother of five and I have never put air in a car tire.  Period.  Ever.  I grew up the middle of three girls.  My dad traveled a lot when I was a teen, so when he was home, he prided himself on helping out with the things he could.  Car maintenance was definitely his baby.  I got married at 21 and happily handed car related issues to my husband.  He has done a fantastic job keeping everything running.  I think the last time my TPMS light came on, I only called him 14 times* before he had that baby to the gas station and the tires filled.

But, with the patience of Job, this very day, my husband taught me how to check my tire pressure and fill the darn things.  In case you, like me, have never checked air pressure or filled a tire before I'll explain how to do it, so you won't feel as dumb as I did.

1. Unscrew the lid off the tire valve stem.

2. Push your air pressure gauge on the value stem securely.  Check your reading.

3. If your tire is low, go to the gas station and pull your car up next to the air pump.  (It's usually around the edge of the gas station.)

4. Snap the air hose onto your tire.  If you hear air leaking, then it's not on correctly.  Fill and go through steps 1 and 2 to check your air pressure again.

5. If you overfilled the tire, or find that it's overfull when you checked your pressure, release air by pushing on the valve stem.  Check the pressure again and--voila!--you're done.

*This may be a slight exaggeration.