RAY: This was from my nouvelle pneumatic series and this was sent in by a long time listener, Chuck Lederer. He writes:

"Last month I dragged my father-in-law to see my son's high school championship basketball game in Kansas where we live. It was about a 75-mile drive each way and I brought along two Best of Car Talk CDs just to make the roadtrip as painful as humanly possible. Fortunately the weather was mild and there was no rain on either leg of the trip.

"After the game, Dad and I began to make the long trip home. At the halfway point the low tire pressure warning light came on on the dash. Most high end cars will tell you which tire is low but my cheap little car did not.

"As soon as I got the chance, I pulled off the highway into a rest area and examined each of the tires in the dark. They all looked the same to me. I crouched down and listened for a hissing sound. No luck.

"I decided to press on hoping the light would just go away. Within a minute the light was back on so I exited the highway and went to a convenience store that had an air hose. There was no gauge, just a warning sign about extremely high line pressure and the need for a tire pressure gauge to avoid dangerous overinflation.

"With great reluctance I asked Dad if he had any ideas. He slowly got out of the car and in the inky shadows of the parking lot, walked around the car pausing for a few seconds at each tire. Dad got back in the car after a minutes and said, "It's the left rear. Put about 5 seconds worth of air in it and see if the light goes off."

I did and it worked. Now he couldn't possibly have seen anything that I didn't see, but how did he know which tire was low?

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