It is recommended to replace your tires in sets of four for all vehicles but particularly important for all-wheel drive vehicles. All four tires should be the same size, brand, tread design, construction and tread depth to prevent differences in the outside diameter of each tire. Even small differences in the outside diameter may cause drivetrain damage or mechanical malfunction.
In vehicles equipped with all-wheel drive (AWD) systems, the transfer case (gears that transfer power from the transmission to both the front and rear axles) and the car’s internal computer work together to send power out to each wheel. The amount of power-per-wheel can vary, depending on each wheel’s individual work load. For example, in a straight line each wheel carries a reasonably similar load. In a cornering situation the stress on each wheel is very different.
So the amount of power the internal computer sends to each wheel – based on what your AWD vehicle needs to go down the road – helps to manage how hard the transmission and transfer case are working.
With inconsistent outside diameters caused by different tire sizes, tread patterns or tread depths an AWD computer’s readings will fluctuate. Various wheels will receive inefficient or incorrect power loads. As a result the drivetrain (computer, transmission and transfer case) must constantly readjust, doing more work than necessary and eventually, may break down. While replacing your tires in sets of fours will greatly reduce your risk of problems, regularly rotating your tires and keeping them properly inflated will ensure your new tires wear evenly. Even tread wear is key to keeping your all-wheel drive system operating at its best!