Locking hubs, also known as free wheeling hubs, play an important role in four wheel drive systems. Usually located on the front wheels of part-time 4WD vehicles, locking hubs are used to engage the front wheels and transform them into drive wheels as needed. Without locking hubs, a vehicle will not be able to enter into four wheel drive mode. In addition, locking hubs are responsible for disengaging a vehicle from four wheel drive. Working hubs on a part-time 4WD vehicle are important if a driver wants the benefits of each drive mode. Four wheel drive allows a motorist to maintain a high level of control when driving on rough terrain and in harsh environmental conditions, while two wheel drive provides better fuel economy and prevents excessive tire wear. Locking hubs are useful because they make switching between these modes possible.