The first thing to look at is tread depth. A penny is an excellent tool forthis. Turn Abraham Lincoln upside down, and stick the penny into the tread groove. If you can see the top of Abe's head, the tire doesn't have enough tread to be safe (or legal, for that matter). Of course, auto supply stores have tread depth gauges that are inexpensive and easy to use.
Tires also have built-in wear indicators: each tread groove will have a four or five spots around the tire that are 2/32 of an inch (the minimum legal tread depth) higher than the rest of the groove. These high spots will create a visible gap in the groove once the tread has worn down to 2/32".
Don't just look at one tread groove, either. Check several, to see if one part of the tire is wearing faster than another. Also, look for "cupping," which is a series of flat spots on the edge of the tread; look at the sidewalls for bulges, which indicate a problem with the tire's internal structure. If you can see wire mesh or threads anywhere, that tire is worse than worn outit may not be safe to drive on. A tire showing any of these conditions needs to be replaced.
A change in your driving pattern may call for new tires before they wear out, however. A move from the Sun Belt to a northern clime may mean you'll be in the market for snow tires; if you'll be using what was previously an off-road vehicle on pavement, you may find you need tires better-suited to asphalt.
Finally, emotion can even play a part in tire buying: you might just like the way a certain tire makes your vehicle look, or you may be very interested in new tire technologies like run-flats.
In the market for a new car? MSN Autos is pleased to provide you with information and services designed to save you time, money and hassle. Click to research prices and specifications on any new car on the market or click to get a free price quote through MSN Autos' New-Car Buying Service.