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When in doubt, tighten lug nuts

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Question: This is the craziest thing I've ever experienced. Two months ago, I had the rear tires replaced on my '92 Ford Explorer. Two days ago, the vehicle was wandering all over the road. I thought I had serious alignment problems, so I looked at each of the tires. The left-rear tire's lug nuts were all loose, and one stud bolt was rolling around inside the hubcap!

I took it back to the garage, and it replaced the broken stud. My first thought was that the mechanic didn't tighten the lug nuts enough when he changed the tire. But the garage said if the lug nuts were loose, it never would have gone for two months of daily driving. The garage told me its wrecker driver has customers sign a waiver every time he changes an aluminum rim on an Explorer, because they have a reputation for coming off.Now the shocker: The garage man said, "Do you remember that wreck on U.S. 127 a month ago? Well, an Explorer rolled over because one of its wheels came off." Is this fact or fiction? -- Andy

Ray: Sounds like fiction to me, Andy. I mean, if you forgot to tighten someone's lug nuts, would you admit it?

Tom: We've never heard of any particular problem with Ford Explorer alloy wheels coming off. And when we checked the National Highway Traffic Safety Administration's list of safety complaints for the '92 Explorer, there were only three out of many hundreds that had to do with wheels coming off. That doesn't suggest an epidemic, since those could have been due to mechanical screw ups as well.

Ray: There is a Technical Service Bulletin concerning the use of power air wrenches on Ford wheels. But that has more to do with the dangers of overtightening than undertightening -- you can warp the brake rotors if you use an air wrench without a device called a "torque stick" that prevents overtightening.

Tom: And it might be that, due to this warning, some mechanics are being so careful NOT to overtighten the lug nuts on Explorers -- because customers come back and scream at them for warping the discs -- that they're being too careful and leaving them too loose.

Ray: I tell the guys in my garage not to worry about overtightening the lug nuts. The way I figure it, if something goes wrong, I'd rather give the guy a new rotor than explain to his widow that I was just being careful not to overtighten anything.

Tom: And it CAN take two months for loose lug nuts to come off. We've seen it happen before. At some point, one nut gets loose enough and comes off, and then things go downhill rapidly. And in many cases, a wheel bolt or two will break, just like yours did.

Ray: There's no way to prove it now, but my guess is that one of two things happened. Either the shop turned down the air pressure on its power tools in order to avoid warping the disc rotors, and simply turned down the pressure too much.

Tom: Or, after tightening the nuts on one side, and maybe part of the second side, the mechanic got a phone call from his wife. Then he went to get some coffee, went to the bathroom, stopped to chat with the secretary, and when he came back to your car, he forgot all about the nuts he hadn't tightened yet.

Ray: But at least you noticed the strange handling and had the good sense to pull over. That's a good lesson for everyone else reading today. If you had kept driving, the wheel almost certainly would have fallen off. And then we might be explaining all this to your heirs instead of you, Andy.

Question: As soon as winter arrived, my sweet wife and I started our yearly battle over running the defroster. Do you recirculate the air within the car, or allow that fresh, freezing, outside air to come in? She claims the outside air prevents fogging and frosting up, but I disagree. Please end this dispute. Thanks. -- Bob

Tom: Oh, Bob, you lucky fellow. Your wife is not only sweet, but smart, too (you were afraid we were going to say that, weren't you?).

Ray: The reason you get fog on the inside of the windows is because moisture inside the car condenses on the glass. The water vapor-- from your breath, your wet shoes or your panting, 120-pound Bernese mountain dog -- hits the cold glass and turns back into water, which is hard to see through.

Tom: If you just leave your ventilation system on "recirculate," you are simply recirculating that same moist air. Whereas if you set the vent on "fresh air," you'll bring in fresh, drier, outside air to replace the moist air that's condensing and fogging up your windows. And believe it or not, even when it's raining, the outside air is drier because you're not adding your breath to it.

Ray: An even better approach is to add the air conditioner to the mix. The air conditioner "conditions" the air -- that is, it removes the moisture. That's one of the reasons it makes you feel cooler and more comfortable in the summer. And if you use the air conditioner along with the defroster on the fresh-air setting, you'll do an even better job of getting the moisture out of the air and, therefore, off the windows.

Tom: Many cars automatically turn on the air conditioner when you select "defrost." But if yours doesn't, go ahead and turn on the AC. You'll be amazed at how much faster the windows clear.

Ray: And using the AC to clear the windows in the winter doesn't mean you have to freeze. You can turn the temperature selector all the way up to hot while the AC is on. This will give you warm, dry air, which is exactly what you want for defrosting. But of course, your wife could've told you that.

The Magliozzi brothers' radio show, "Car Talk," can be heard Saturdays at 10 a.m. and Sundays at noon on KUER FM 90.1, and on KCPW 88.3/105.1 FM Saturdays at 9 a.m. and Sundays at 10 a.m. If you have a question about cars, write to Click and Clack Talk Cars c/o King Features Syndicate, 235 East 45th St., New York, N.Y. 10017. You can e-mail them by visiting their Web site at http://cartalk.com.