Accessories

The truth about tire treadwear

iStock

 (iStock)

The amount of tread on a tire is critical in determining how well it will vacate water to maintain contact with the road in the rain. If your tires wear out quickly, your safety may be at risk.

Our research tells us that when people shop for tires, their primary considerations are price, availability, and treadwear. Prices are easy to find. But until now, consumers had to rely on the government’s treadwear ratings or mileage warranty claims from manufacturers­—if available­—to judge how well tires would wear.

That’s why Consumer Reports tests two tires per model over six months of driving 16,000 miles on public roads through the scrub grass of West Texas. In the past, we scored treadwear on our standard five-point scale. Now we list projected mileage based on how tires wear in our tests. (See our tread-life mileage, and much more, in our tire Ratings.)  

Of course, there’s more to a good tire than long life. But longevity is a key to whether a tire you’re considering is a good deal.

Noteworthy in the findings is that almost half of the 47 all-season and performance all-season tires could last at least 65,000 miles; a half dozen could top 85,000 miles or more. And there’s a wallet-friendly surprise: Tires with the longest life don’t necessarily cost the most. (Learn how to extend tire life.)

Do Tire Tread Warranties Wear Thin?

Many replacement tires, especially the all-season ones that come standard on a car, minivan, or SUV, have a prorated mileage warranty. It’s based on how long the tread on a tire is expected to last. For the tires we tested, it was usually between 40,000 and 90,000 miles.

But those warranties often don’t offer the consumer much payback if the tires wear out prematurely. The warranty is sometimes more of a marketing boast than a useful measure of longevity.

Why is that? Well, if tires wear out before the warranty mileage is used up, you’ll probably get only a fractional credit representing the miles the tires didn’t cover. And that’s good only toward the purchase of identical or comparable tires from the same manufacturer—which you may not want. You can’t use it to get better tires or tires from another brand

Here’s where the math really doesn’t add up: The credit can be applied to a manufacturer’s suggested retail price for a new tire or to a dealer’s price. And that price is often high relative to the frequent discounts offered by many retailers. In fact, you may be able to buy new, discounted tires for less than the price of warranty replacements.

On top of that, restrictions to get your prorated credit abound. Your tires may have to show even wear across the tread or the deal’s off. You may also have to show receipts that verify you had the tires rotated at the prescribed intervals, usually every 5,000 miles, since they were new.

The tires also have to be worn out, which is defined as having a tread depth of only about 2/32 inch. Tires that are worn out will perform poorly on wet roads and could pose a safety risk. (Use these tips for safer winter driving.)

Our controlled tread-life tests cut through the marketing mumbo-jumbo to tell you how many miles your tires will last before becoming worn out. Of course, your actual experience will vary according to the vehicle you drive, how and where you drive, and other factors.

The Writing on the Wall

Tires have a wealth of information encoded on their sidewalls. When replacing them, we recommend staying with the size and speed rating of your car’s original tires. Consult your owner’s manual for additional information.

Size

On the tire at right, “215” is the cross-section width in millimeters; 60 is the ratio of sidewall height to its width (60 percent); R indicates radial-ply construction; and 16 is the wheel rim’s diameter in inches.

Load index

'Shorthand for the weight each tire can carry safely. The 94 here means 1,477 pounds per tire­—pretty typical for a midsized car tire. That’s the maximum tire load at the maximum pressure.

Speed rating

A letter denoting the tire’s maximum speed when carrying the load defined by the load index­—and not how fast you should drive! Standard all-seasons are usually rated S (112 mph) or T (118 mph). Climbing up the scale are the letters H (130 mph), V (149 mph), ZR (149+ mph), W (168 mph), and Y (186 mph). Winter tires may carry the letter Q (99 mph) or higher.

Treadwear grade

A government-required number that indicates a tire’s expected wear. A grade of 300 denotes a tire that will wear three times as well as a tire graded 100. But the numbers are assigned by tire manufacturers, not an independent third party.

Traction and temperature scores

Those scores denote a tire’s wet-stopping ability and temperature resistance. For traction, AA is best, C is worst. For temperature resistance, scores range from A (best) to C.

This article also appeared in the November 2015 issue of Consumer Reports magazine.

Copyright © 2005-2015 Consumers Union of U.S., Inc. No reproduction, in whole or in part, without written permission. Consumer Reports has no relationship with any advertisers on this site.