Q Does cold weather cause flat tires?

A Yes, it can. Cold weather causes air in tires to contract -- a pound of pressure per square inch for each 10-degree drop in temperature. If your tire pressure was low to begin with, you might have trouble.

Subzero temperatures can make the rubber of the tire stiff and cause the seal or "bead" (where the rubber meets the metal rim) to loosen. The resulting air leak can make the tire flat. Sometimes the valve, which is also rubber, will leak.

Even a tire with an embedded nail or debris may drive fine until cold weather arrives. That's because extreme cold makes the tire contract away from the nail, opening a hole, causing a leak and then a flat.

Aluminum alloy wheels also are more likely to leak, and they're used on most cars today. It's harder to get a good seal on alloy wheels. Road salt eats away at the metal, leaving an uneven surface that's prone to air leakage. And the jarring and jostling from hitting potholes doesn't help.

The best way to prevent a cold-weather flat is to keep an eye on tire pressure. Walk around your vehicle before you get behind the wheel. Check tire pressure regularly, at least once a month, experts advise. In addition to preventing flats, proper tire maintenance enhances road safety and gas mileage.

To get top off, cool it

Q I have a Christmas-themed sterling silver martini pitcher that I would like to use, but I am unable to get the top off. Can you suggest a way to loosen the top to make the pitcher usable?

A Put the pitcher in the coldest part of your refrigerator (not the freezer!) for a day. (Usually, that's the lower part because cold air is heavy and falls.) Remove it. The top should come off.

If not, try the opposite. Hold the pitcher under warm water long enough to warm the inside. That should increase the temperature inside the pitcher enough to cause pressure that will help you remove the top. You might also try prying it off with a wooden spoon covered with cloth.

Send your questions to Fixit in care of the St.ar Tribune, 425 Portland Av. S., Minneapolis, MN 55488, or call 612-673-7032, or e-mail fixit@startribune.com. Past columns are available at www.startribune.com/fixit. Sorry, Fixit cannot supply individual replies.