At a time when technology is so advanced that we’re moving toward cars that drive themselves, it’s easy to overlook tires. In fact, they are packed with their own advanced technology: Tire materials, design, and construction have come a long way, and the safe working life of a typical set of tires is longer than ever.

Still, they do wear out. It’s time to replace your tires when they wear down to 1/16 inch of tread. They’ve reached this level when tire tread is even with the wear bars built into the tread. You can also measure the tread with a penny: Insert it Lincoln-head-first in a tread groove; if the treads don’t cover part of Abe’s head, they are worn down too far.

If you don’t drive much, you might need to replace your tires before their tread is worn. Tires dry out as they age, reducing performance and safety. Many car manufacturers recommend replacing tires after six years, regardless of tread wear.

Regardless of tread wear or age, replace a tire if you see a bulge or blister on the sidewall; and if you see cuts or cracking, have an expert inspect it.

When you need new tires, you can choose from tire specialty outlets, online sources, independent shops and new-car dealers. But where can you get the most for your money? Undercover shoppers for Delaware Valley Consumers’ Checkbook collected prices on popular name-brand tires from local and online operators, and found that it pays to shop— you can save hundreds for the effort. You can access Checkbook’s report on tire prices, plus get free access to all of Checkbook’s ratings, until April 4 at Checkbook.org/Inquirer/Tires.

Here’s what Checkbook’s shoppers found:

Major price differences: For example, Checkbook’s shoppers were quoted prices for a set of four Michelin Latitude Tour tires for a Ford Explorer that ranged from $660 at Eppie’s Discount Tire, $745 at Mill Street Tire, and $784 at BJ’s, to $1,217 at Creamery Tire.

Among the Delaware Valley-area stores that Checkbook shopped, chains BJ’s, Costco, and Walmart offered low overall prices, but its shoppers also found low prices at some independent tire dealers, repair shops, and even new-car dealerships. The lowest prices were quoted by Eppie’s Discount Tire in Philadelphia and United Tire & Service in Downingtown. Although BJ’s, Costco, and Walmart offered low prices, a big advantage to using a conventional tire shop is that selection at the big-box discounters is fairly limited.

Not all of the big chains or big-box stores offered low prices: Surveyed stores for Firestone Complete Auto Care, Just Tires, Mavis Discount Tire, Mr. Tire, NTB, Pep Boys, Sam’s Club, Sears, and Tires Plus quoted prices that ranged from slightly below average to higher than average.

Online sellers Amazon and Online-Tires.com also offered consistently low prices — with incomparable selection: These retailers will ship tires to your home or to a local shop for installation. Among the online sellers Checkbook shopped, Amazon’s prices were the lowest — about 4 percent lower than prices offered by OnlineTires.com and 7 percent lower than TireRack.com’s.

When shopping for price, specify exactly what you want: If you want mounting, balancing, and valve stems to be included, make that clear. And because there are so many tire models, many with very similar names and specifications, cite the tire model precisely, preferably by the parts number.

You can still get great installation service if you buy online: If you order tires from a low-priced online seller such as Amazon, have them shipped to a top-rated repair shop (Checkbook also evaluates hundreds of local garages for quality and price). Not all repair shops install tires, but many do, and most accept tire deliveries from online retailers.

Avoid pricey extras: While shopping for tires, you may be offered road-hazard coverage. Some stores, including Costco, provide this type of coverage for free, but many charge an extra $40 to $75 to cover a set of four tires.

The protection covers damage to tires due to road hazards during normal driving. If you get a flat caused by a nail, glass, or other road debris, the company promises to repair or, if necessary, replace the tire. But if you get a flat from accidentally running over a curb or other driver-caused errors, you get nothing. And these plans never pay for failure from worn tread; that type of problem is poorly covered under the manufacturer’s warranty.

Unless they’re free, these plans aren’t good deals. If a nail flattens your tire, a shop will charge only $20 or so to plug and repair it. Just as you can’t predict when or where you’ll have a flat, you can’t predict which tire will get one, so you’ll have to buy the plan for all four. Thus, you’d be paying $60 or so to protect yourself against having to pay $20 or so for each tire repair you may never need. As with any type of “protection plan” pushed by big-ticket sellers, what you’re really being offered is insurance that is highly profitable for the seller but provides little benefit to the buyer.

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Delaware Valley Consumers’ Checkbook is a nonprofit organization with a mission to help consumers get the best service and lowest prices. It is supported by consumers and takes no money from the service providers it evaluates.