4WD and AWD Tire Concerns

AAA Auto Repair Article
By AAA Automotive
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Flat tires—not only can they throw a curveball into your day, but they can put a dent in your wallet when the problem can’t be fixed with a simple puncture repair. And if you happen to be the owner of a four-wheel-drive (4WD) or all-wheel-drive (AWD) vehicle, you may have to swap out not just one, but two or even all four tires.

Why would you need to replace other tires that have a good tread remaining when only one tire is bad? The answer is that tire-size variations can have a major effect on the durability of modern 4WD and AWD systems.

A tire’s size, or more specifically its circumference, is important because a larger tire travels further with each rotation than a smaller tire. Although such variations may seem insignificant to the naked eye, they cause various 4WD and AWD drivetrain components to rotate at different speeds, which increases wear.

But that’s not the only problem. On some AWD cars, a circumference variation of more than one quarter inch between all four tires will result in expensive transmission or drivetrain component failure within a short time.

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There are also potential safety issues. Most modern 4WD and AWD systems are computer-controlled and come on vehicles that are also equipped with anti-lock brakes, traction control and stability control. These safety systems require accurate wheel rotational speed information to work properly; if tire size variations result in conflicting wheel speed signals, the systems could perform poorly or be disabled.

To reduce your chances of tire-related issues on 4WD and AWD vehicles:

Check your tire pressures at least once a month and keep all four tires inflated to the vehicle manufacturer’s specifications. This information can be found in the owner’s manual or on the driver’s door jamb.

Rotate the tires at your automaker’s recommended interval—generally every 6,000 to 7,500 miles—and in the recommended pattern. This will help equalize wear and prevent significant circumference variations.

Fit 4WD and AWD vehicles with matching tires so that all four tires are the same brand, model and size, and have the same degree of wear. If you are installing anything less than a full set of new tires, always consult the owner’s manual, a qualified tire installer or a dealership to make sure any size variations will not create problems down the road.

Take the scare out of auto repair by choosing a trustworthy AAA Approved Auto Repair facility. These shops adhere to a strict set of standards and are inspected annually to ensure professional service. To locate a facility near you, visit AAA.com/AutoRepair.
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