It can all begin with the Lincoln test: if you see the top of Abe's head when you place a penny upside down into the tread of a tire, it's time to go tire shopping. The passage of time, or damage and flaking on the sides of the tires, can also signal the need.
It can end up costing a pretty penny — usually $500 to $800 for a set of four.
1. Get the right size. A tire's size is listed on its sidewalls in a sequence such as P265/70R16. Replacement tires should always match what's noted in your owner's manual or car door jamb, not necessarily what's currently on your vehicle.
2. Age matters, even with "new" tires. Tires naturally deteriorate over time, faster in hot climates. A tire's "birthday" is noted as a four-digit number following a letter sequence beginning with DOT, indicating the week and year it was manufactured — 5009, for instance, means the 50th week of 2009.
Vehicle manufacturers recommend you replace tires after six years, no matter what their condition. Since some shops stock old tires, check the age code to make sure you're not being sold ones that are already several years old and well on their way to needing replacement.
3. Learn the lingo. "All-season" tires are a popular and wise choice for most drivers. But think those called "high-performance" or "ultra high-performance" are better? Think again. Tire performance means ability to handle well at higher speeds, not lifespan. Any tire with "high-performance" in its name will likely wear out quicker.
4. Think twice about warranty. Manufacturers often tout mileage warranties — typically between 50,000 to 80,000 miles, depending on tire type. The mechanic whom I use, however, says, "In truth, drivers never get that kind of mileage from their tires. And the heavier the vehicle, the less you should expect — no matter how well you drive."
Before buying based on mileage warranties, know the fine-print details: If tires wear out prematurely, you don't just get a new set for free. There's a prorated credit for replacements, and for that, you'll likely be expected to prove you properly cared for the tires by keeping them inflated to the right pressure, aligned and rotated every 5,000 to 7,500 miles. There may be a careful inspection and demand for service records before warranties are honored.
5. Don't rely on the TPMS. If your vehicle was manufactured in 2008 or later, chances are it has a Tire Pressure Monitoring System, which warns when tires are underinflated. Insufficient air pressure not only is a safety hazard but speeds tire wear.
So at any given time, why do a majority of cars have at least one underinflated tire? "Most people never check their tire pressure," says Mark Cook of the Tire Industry Association, and the pressure monitoring system gives a warning only when tires are underinflated by 25 percent or more, not lesser amounts that still affect tread wear and tire lifespan.
To make your tires last longer, take five minutes every month to ensure that they're inflated according to specs listed on the car's door jamb. What's noted on the tires themselves is the maximum allowable pressure, not the pressure you want.
This isn't to say that a pressure monitoring system isn't worth keeping in good working order. Keep in mind that its brains are in special tire valves. They cost about $50 each and should be replaced every three to five years, says Cook.
6. Know how and where to bargain. Tires are expensive but can you dicker for a discount? You certainly should try, but good luck.
Your auto dealer or neighborhood garage will likely offer zero or very low discounts, claiming thin profit margins.
Because of their buying power, warehouse clubs such as Costco and BJ's sell many tires for less. But aside from coupon sales, don't expect to successfully bargain down here. Sales clerks at chains that specialize in tires tend to work on commission, so they may have more wiggle room or will make "match any price" offers.
Websites that sell tires (for shipment to local installers) are worth checking out too. Type "buy tires online" into a search engine to find these sites.
Overall, you'll fare best seeking a discount not on the tire, but on related services such as installation, lifetime tire rotations or oil change. Expect salesmen (who sometimes must meet sales quotas) to push for more expensive tack-ons such as brake jobs and alignments. If your car needs them, ask for a discount on them as part of your tire purchase.
Sid Kirchheimer writes about consumer issues.