Shopping for tires
Where the rubber meets the road, shopping by price can really cost you.
March 6, 2002: 5:58 p.m. ET
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NEW YORK (CNN/Money) - Car owners typically consider the appearance and the performance of their cars and even the grade of gasoline they put in the tank -- but they rarely spared a thought for their tires. Then came last year's controversy over fatal accidents involving Ford Explorers equipped with Firestone tires.
Whatever the outcome of the lawsuits still buzzing around the Explorer accidents, those fatalities were a stark reminder how important tires are.
Most people don't worry about the tires that come with a new car, and with good reason. But if you put 40,000 miles on that car -- or buy a used car --you will probably have to make a decision about new tires. Though most people don't know it, tires -- even those in the same price-range -- vary considerably in their expected life, their traction, and their resistance to dangerous high temperatures.
Fortunately, there are easy ways to find out all those qualities on almost any tire you would consider buying. It isn't as simple as just spending more money for better tires or relying on a top brand (after all, Firestone was a well-established brand).
When should I replace my tires?
Manufacturers' recommendations -- and state law in many cases -- call for tires to be replaced when the tread depth wears down to 1/16 inch. (When new, tread depth is 2/5 to 1/2 inch). That means that most drivers need to think about new tires roughly every 40,000 to 50,000 miles. When you reach 1/16 inch, you will see the "wear bars," rubber strips that usually are darker than the tire. If your tires are getting worn but you don't see the bars, stick a penny into the tire tread, Lincoln's head first. If the tread fails to reach the top of his head, you are getting close to that 1/16 level.
To be sure you are safe, I would replace tires even sooner -- around the 1/8 inch tread level (the top of Lincoln's forehead in the penny test). With balding tires, stopping can take longer. And with shallow treads, water can't escape through the tire's grooves, which could put you into a dangerous slide as you brake on a wet road.
Should I buy exactly the same tires that came from the factory?
Not necessarily, though you do need to stick with the same size. You might want to change brands to save money or, alternatively, spend more for tires with superior traction and high-speed capability. More expensive performance tires, designed to grip better at high speeds and in difficult cornering, will cost from $75 to $105 per tire vs. the $50 to $75 you would pay for the standard all-weather tires that come on most new models.
Start with your current tires to get the size. The numbers and letters on the sidewalls tell the story, if you know the code. In a confounding mix of millimeters and inches, you will see something like 185/60R14. This means the tire is 185 millimeters (7.28 inches) wide, that the ratio of sidewall height to width is 0.6 and that the diameter of the wheel is 14 inches. (The R means it's a radial tire.) You don't have to remember what these mean -- just copy them down exactly. If your tires are too worn to read, web sites like Tirerack.com and Discount Tire Direct will tell you the correct size if you enter your car's year, make and model.
Compare tires
To compare tires, go to the National Highway Traffic Safety web site. This site gives the various UTQG (uniform quality tire grading) ratings for tires. These ratings are also printed on the sidewall of the tire itself.
The most important rating is traction -- how well a tire will stop you on wet pavement. With possible ratings of AA, A, B and C, consider only tires with the two top ratings. Otherwise, you are gambling with your safety.
If you commute in your car every day or otherwise rack up big mileage, pay special attention to the tread-wear rating. With 100 as the minimum acceptable standard, look for a rating of 300 or better.
If you drive a lot at Interstate speeds or do heavy hauling or towing, temperature resistance is especially important. If you fit that description, look for an A-rated tire. With a range of A, B and C, look for B or better regardless of your driving profile. The temperature rating is an especially important safety indicator, since overheated tires can blow out or otherwise cause accidents. In many of the Firestone/Explorer accidents, the tread separated from the tire during highway driving, often in hot-weather states like Texas and Florida.
In fact, the tire involved in many of these accidents, the Firestone Wilderness A/T was rated only C for temperature resistance on the NHTSA site. Most brands make tires with a range of heat-resistance ratings. But two premium brands, Michelin and Pirelli, had all A or better for traction and B or better in temperature ratings.
Another short series of numbers and letters show the tire's load index and speed rating. Let's say your tire had 87S. The load rating of 87 means your tires could handle a total load of about 1,200 pounds. This increases irregularly at the rate of about 40 pounds per rating point so that a 100 rating, for instance, means the tire can carry about 1,765 pounds.
The S here is the tire's speed rating. It means the tires can run safely at 112 mph (not that anyone recommends that, of course.) Letters earlier in the alphabet mean lower speeds. For example, N equals 87 mph). Letters later in the alphabet mean higher speeds up to 186 mph for Y.
Do you need snow tires? If you drive more than a few days each winter on ice or snow, yes. If you got stuck in snow anytime in the last two years, the answer is "yes." On the other hand, changing your tires twice a year is a lot of bother if you only rarely need the snow tires. Tirerack.com has a discussion posted of how to choose snow tires.
Going shopping
Check the NHTSA ratings and web site reviews and decide on two or three different tires you would consider. Then start looking at price. Says Noble Bowie, who has supervised the NHTSA tire program: "You may be able to get tires of comparable performance for less if you do some shopping." The two web sites that sell tires, Tire Rack and Discount Tire Direct, will have the best base prices, but remember to add $6 to $9 per tire for shipping and $10 to $15 per tire for installation at a local shop.
If you want to get some advice in person, try a specialty tire store -- either an independent local business or a chain such as Discount Tire or Tire Kingdom. If you know exactly what you want, Sears and WalMart have large selections of tires. Prices in these stores can be especially attractive if you catch a sale on the tires you are looking for.
Here's a final piece of good advice: Once you have those tires, check the pressure every other time you fill up with gas. I don't mean to sound like a nag, but checking tire pressure can save your life. Under-inflated tires heat up more readily. And as we have seen, overheated tires are dangerous. 
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