What happens if you dont replace all four tires on an AWD?
Replacing only two of the four tires on an all‑wheel‑drive (AWD) vehicle can place unusual stress on the drivetrain and alter handling. In most cases, the safest approach is to replace all four tires at once; if that isn’t possible, you should follow gear‑level guidelines to minimize risk and safeguard the system.
AWD systems rely on tires rolling at very similar diameters to distribute torque evenly. When tires differ significantly in size or tread depth, the difference in rotation speeds can cause the center differential or transfer case to work harder, trigger stability controls, and accelerate wear on driveline components. Tire choice and diameter differences matter for performance, safety, and longevity—not just tread depth.
Why matching tires matter on AWD
Most AWD setups use a center differential or a clutch‑pack to distribute power between front and rear axles. When one tire wears more or is a different size than another, it changes the overall rolling circumference on that axle. The system then tries to compensate, which can wind up the driveline, heat components, and wear parts unevenly. In some vehicles, this can also confuse wheel‑speed sensors, affecting ABS, stability control, and traction control.
What happens if you don't replace all four tires
Below are the most common risks you face when you don’t replace all four tires on an AWD vehicle.
- Drivetrain wind‑up and stress on the center differential or transfer case, potentially accelerating wear or causing failure.
- Uneven tire wear and accelerated wear on the driveline due to differing rolling diameters between axles.
- Altered handling and stability, with potential surprises in wet or slippery conditions as wheel speeds diverge from what the system expects.
- Tripping of safety systems (ABS, stability/traction control) or false activations due to inaccurate wheel‑speed readings.
- Speedometer and odometer inaccuracies if tire circumferences differ significantly from the original specification.
In practice, the right answer depends on your vehicle’s specific AWD design and the degree of circumference difference. If you must mix tires, the differences should be minimized and the installation should follow manufacturer guidance as closely as possible.
In short, mixing tires on an AWD can lead to mechanical wear, compromised safety features, and altered handling. Replacing all four tires at once is the clearest path to preserving AWD performance and longevity.
Practical guidance if you can’t replace all four wheels at once
If replacing every tire isn’t feasible right away, here are commonly recommended steps to reduce risk on most AWD cars. Always check your owner’s manual for the model‑specific guidance.
- Install the two new tires on the rear axle. This placement helps maintain stability and reduces the chance of oversteer when the front tires are still older or more worn.
- Make sure the two new tires are the same size, tire model, and ideally the same brand as each other. If the old tires are a different brand or model, aim for the closest match in size and rolling diameter to minimize differences.
- Keep the remaining two older tires on the axle with the most load or those with greater tread depth variance, and monitor overall tread depth to keep the difference within a small range (generally within a few millimeters).
- After installation, have the tire balance checked and consider an alignment if you notice unusual vibrations or pulling. Some vehicles may require a reset or recalibration of the AWD system’s sensors.
- Drive cautiously and slowly‑varying speeds for the first few hundred miles, and recheck tire pressure and tread depth regularly until you can replace all four.
These steps can reduce risk, but they are not a perfect substitute for four matching tires. When feasible, replace all four tires to restore uniform rolling diameter across the vehicle.
Cost, safety, and warranty considerations
Replacing all four tires at once is often the most cost‑effective long‑term choice because it minimizes wear on the drivetrain and helps preserve warranty coverage that may rely on proper maintenance practices. If a drivetrain component is damaged due to mismatched tires, repairs can be expensive and may not be covered under warranty. Always consult your vehicle’s manual and the tire manufacturer recommendations, and consider speaking with a dealership or certified tire tech for model‑specific guidance.
Summary: For AWD vehicles, uniform tire size and tread depth across all four tires are essential for protecting the drivetrain and ensuring predictable handling. Replacing all four tires at once is the simplest, safest route. If you must replace fewer, install new tires on the rear axle, minimize circumference differences, and follow up with a professional inspection and, when possible, a full four‑tire replacement.
