If you've been to an auto parts store lately, you've probably seen those cute little plastic caps near the cash register. In fact, I've seen the little tire pressure monitoring caps all over the place. These plastic valve caps claim that they can monitor your tire pressure for you, alerting you if your tires drop below a predetermined tire pressure. They do this with no batteries or electronics of any sort. And they claim to do all this for less than ten dollars.

My brother and I had a few laughs over these little caps, but decided we should pick up a set for review. We bought the caps with a preset pressure setting of 36 psi. Ours ran a paltry $5.99 at Advance Auto Parts. We got back to the shop and, just to be fair, set a few tires to test pressures. Still rolling our eyes, we screwed the grey caps with clear tops onto the valve stems. You can check out the results of our tire pressure monitoring caps test.

Update: After running this test, we received emails from some readers who say that have experienced failure in these caps, causing leaks and flat tires. We're leaving our caps installed to see what happens in the long term. Stay tuned.