Dear Tom and Ray:

A friend of mine took her Saturn to a mechanic, as the car was running a bit rough and the road noise was loud. He examined the car and told her that the dealership had improperly installed directional tires on her car. Apparently, the tires are supposed to go one way, and when installed improperly, they are ruined. She spent close to $300 for new tires. When she told me the story, I laughed so hard that I had tears in my eyes, and I think I had gastric distress. Is there such a thing as directional tires, or is this a con? I mean, all tires are round, right? And what happens if you drive in reverse with directional tires -- does that ruin them? Anyway, my friend and I have placed a high-stakes wager. Who is correct, me or my directionally challenged tire friend? -- Joe

TOM: Well, I hope the stakes weren't too high, Joe, because you lost, buddy. There certainly are directional tires.

RAY: Some higher-end performance tires are designed to perform best in one direction only. When you design a tire, if it has to be perfectly symmetrical and work equally well rolling both ways, you have to compromise when you set up the orientation of the grooves. On the other hand, if you know it's only going to turn in one direction -- and water and slush only have to be channeled in one direction -- you can optimize it for that direction.

TOM: But as far as we know, installing a directional tire backward will not ruin it. Nor will it cause a car to run rough or handle dangerously. It simply won't give you its optimal performance. On the Naughty Activity Scale, it rates just above removing the mattress tag that reads "Do Not Remove." Most drivers wouldn't even notice the difference during normal day-to-day driving.

RAY: So, it's entirely possible that your friend simply had worn-out tires -- directional or not. And worn-out tires, especially when they get cupped, get very noisy and can make the car handle poorly.

TOM: In any case, you owe your friend an apology, Joe. But don't worry. I'm sure you're going to look great in that flowered apron, cleaning her house for the next six months.