Yes, using mismatched tires can absolutely damage the all-wheel drive (AWD) system over time. The primary risk comes from differences in the tires' overall diameter, even minor ones. An AWD system is designed to send power evenly to all four wheels. If the tires have different diameters, they will rotate at slightly different speeds. The system's differentials and center clutch pack will constantly fight this difference, leading to excessive heat, premature wear, and potentially catastrophic failure of these expensive components.
The critical factor is the tread depth difference, which directly affects diameter. Most vehicle manufacturers specify a maximum allowable difference, typically 2/32 to 4/32 of an inch between any two tires. For example, if one tire is new (10/32") and its opposite is worn (6/32"), the 4/32" difference can be enough to cause "wind-up" stress on the drivetrain.
| Scenario | Tread Depth (Front) | Tread Depth (Rear) | Tread Difference | Risk Level for AWD System |
|---|
| Ideal (New Set) | 10/32" | 10/32" | 0/32" | None |
| Moderate Risk | 9/32" | 7/32" | 2/32" | Low, but monitor |
| High Risk | 10/32" | 6/32" | 4/32" | High, potential for damage |
| Critical Risk | 10/32" | 4/32" | 6/32" | Very High, avoid driving |
| Mismatched Brands | 10/32" (Model A) | 10/32" (Model B) | Varies | High (due to design differences) |
The safest practice is to replace all four tires at once. If you must replace only two, the new tires should be installed on the rear axle, and the older tires should be shaved down by a professional to match the tread depth of the new ones—a service some tire shops offer. Never mix different tire models, sizes, or types (e.g., all-season with winter) on an AWD vehicle, as their construction and grip levels can differ even if the size is labeled the same.
