It vary depending on your car's drivetrain. A vehicle with front or rear-wheel drive does not need all tires changed at once. Consider replacing both front tires if one needs to be replaced. This will match the tread patterns on both sides of the car. This improves highway handling and car alignment. AWD Tire Replacement: Always change all four tires on an all-wheel-drive vehicle. Drivetrain damage can occur in vehicles with mismatched tire depths. The car's computer assumes all treads match and sends signals to each tire to do as told. Due to this data's inaccuracy, each tire would receive the wrong information. Whether your car is two- or all-wheel drive, you must follow the manufacturer's tire rotation plan. Hence, the tires will wear evenly and function better.