A beam axle is a suspension system, also called a solid axle, in which one set of wheels is connected laterally by a single beam or shaft. A live axle is a type of beam axle in which the shaft (or shafts, since live axles, while connected to move as a single unit, are seldom one piece) also transmits power to the wheels; a beam axle that does not also transmit power is sometimes called a dead axle. Beam axles are commonly used at the rear wheels of a vehicle.
The principal advantage of the beam axle is that it is simple and cheap to manufacture. It also engages little or no interior volume within the vehicle. Its drawbacks are that it does not allow each wheel to move independently in response to bumps, and the mass of the beam is part of the unsprung weight of the vehicle, which can further reduce ride quality.
Beam axles have an important advantage for off road applications, as it provides better vehicle articulation. They are also generally stronger and less prone to failure in a high load environement, such as for off-roading.