Replacement Tires for AWD and Four-Wheel Drive Vehicles

Wednesday, February 19, 2014 by Neal O'Neal

It's been a rough winter season for most of the country. Looking at roads across the northern part of the United States reflects this. Tire damage due to potholes or curb damage is not uncommon. For most, a single tire replacement is fine. However, when dealing with an all-wheel drive or four-wheel drive vehicle, replacing one tire may not be the best solution.

These vehicles divide the engine's horsepower between its four tires to help aid in traction. In order to transfer this extra power, the vehicle's driveline mechanically connects the tires so they work in unison. Due to this connection, it's very important that the tires are closely matched in diameters. Tires with different diameters roll a different number of times per mile - which is a result of variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths.

As an example of different tire diameters resulting from tires worn to different tread depths, we compared two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire had a calculated diameter of 24.97", a circumference of 78.44" and rolled 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth was calculated to be 1/8" shorter with a diameter of 24.84", had a circumference of 78.04" and rolled 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting four revolutions per mile difference can place continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain. Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. This is another reason to keep an eye on your air pressures.

We offer a tire shaving service that allows a single tire to be shaved down to the tread depth of the remaining three tires on your vehicle. This is done by removing tread rubber from a new tire on a specialized machine that operates as a tire lathe. While the cost of our street tire shaving service will range between $25 and $35 per tire, it's significantly less than the cost of unnecessarily replacing the remaining good tires with lots of mileage still available from them.

To learn more about the importance of having the same tread depth levels on your vehicle's tires, read "Matching Tires on Four-Wheel Drive and All-Wheel Drive Vehicles."

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