The mysterious, 140 year-old, never-changing automotive part.

May 01, 2006

RAY: In the 1870's, there came into existence something that I would have to call a fundamental automotive invention. And this is fascinating, because it pre-dated the discovery of the automobile by a couple of decades.

You might think the automobile was invented, but it was really discovered. The light bulb was invented. The radial arm saw was invented, but not the automobile.

This device was not developed for the automobile, but it wasn't long before every single automobile manufacturer began using it. In fact, every car driven everywhere in the world today uses this device-- and not just one of them, but several.

Here's the interesting part: In over 100 years of use, the basic design has not changed. Even more interesting, in the 1890's or 1900's, when the thing began to be used widely, it cost a dime. In 2006, it costs a dime.

There are plenty of hints here, and hardly any obfuscation, but I'll give you one more hint: Most cars today use 6 or 7 of these.

What is it?
RAY: The device is most commonly found in the stem of your tires, and it's called a Schrader valve. It's a little valve that keeps the air in, and allows you to add more air by depressing the stem of the valve, or let air out if need be.
Right now, you're probably saying, "My car has four tires and a spare. How can I have six or seven of these valves?" Well, your air conditioning system has one, and lots of cars have one as a test port in the fuel rail, to be able to hook up a pressure gauge.

So, your car could easily have seven of these, even though it has only five wheels. Do we have a winner?

TOM: We do! The winner this week is Alison Haskins from Oxford, Ohio. And for having her answer selected at random from among all the correct answers that we got, Alison gets a 26-dollar gift certificate to the Shameless Commerce Division at, where she can get her mom a copy of our mothers and cars CD collection, called 'Maternal Combustion.' Actually a gift like this might be better for your mother-in-law. Nothing says, "I'm not really that fond of you," like a Car Talk CD. Don't you think?

RAY: Well, that's true.

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