Ideally, it is best to replace all four tires at once so that every tire’s size and profile matches one another. However, it’s not always the most economical to replace all four tires, especially when perhaps only two tires are worn and the other two tires still have good tread depth. No matter if your car is FWD, RWD, or AWD/4WD, it is the recommended to install a pair of brand new tires on the rear axle of the vehicle.