A beam axle is a suspension
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...
system, also called a solid axle, in which one set of wheels is connected laterally by a single beam or shaft. A live axle
A live axle, sometimes called a solid axle, is a type of beam axle suspension system that uses the driveshafts that transmit power to the wheels to connect the wheels laterally so that they move together as a unit....
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, but historically they have also been used as front axles in rear wheel drive cars. Ford used beam axles across the range until 1949, only being phased out in Europe as recently as the early 1960s with the Ford Popular
The Ford Popular is best known as a car from Ford built in England between 1953 and 1962. When launched, it was Britain's lowest priced car.The name Popular was also used by Ford to describe its 1930s Y Type model...
being suspended (though the 100E was fitted with MacPherson strut
The MacPherson strut is a type of car suspension system which uses the axis of a telescopic damper as the upper steering pivot. It is widely used in modern vehicles and named after Earle S. MacPherson, who developed the design.-History:...
Beam axles are typically suspended either by leaf spring
Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles...
s or coil spring
A Coil spring, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces...
s. In some cases, a Panhard rod
A Panhard rod is a component of a car suspension system that provides lateral location of the axle...
or similar device may be used to control the lateral motion of the axle.
A similar suspension is the Twist-beam rear suspension
Twist-beam rear suspension
The twist-beam rear suspension, also known as torsion-beam axle is a type of automobile suspension based on a large H or C shaped member. The front of the H attaches to the body via rubber bushings, and the rear of the H carries each stub-axle assembly, on each side of the car...
, in which the beam axle also functions as an anti-roll bar
A sway bar or anti-roll bar or stabilizer bar is a part of an automobile suspension that helps reduce the roll of a vehicle that is induced by cornering or road irregularities. It connects opposite wheels together through short lever arms linked by a torsion spring...
to control the roll motion of the body.
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
In a ground vehicle with a suspension, the unsprung weight is the mass of the suspension, wheels or tracks , and other components directly connected to them, rather than supported by the suspension...
of the vehicle, which can further reduce ride quality
Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road...
Because beam axles do not ever exhibit any camber change as the suspension travels, they are ideal for carrying heavy or varying loads. Although this negatively impacts cornering compared to other suspension designs (because the wheels have zero camber gain during body roll), beam axles are nearly universally used in heavy-duty trucks. One notable exception is the Czech manufacturer Tatra, who instead use swing-axles in conjunction with a central 'backbone' chassis. Most light and medium duty pickup truck
A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...
s and van
A van is a kind of vehicle used for transporting goods or groups of people.In British English usage, it can be either specially designed or based on a saloon or sedan car, the latter type often including derivatives with open backs...
s also use a beam axle, at least in the rear.
Beam axles have an important advantage for off-road
An off-road vehicle is considered to be any type of vehicle which is capable of driving on and off paved or gravel surface. It is generally characterized by having large tires with deep, open treads, a flexible suspension, or even caterpillar tracks...
applications, as they provide better vehicle articulation
Ramp travel index
Ramp travel index or RTI, is a way of measuring a vehicle's ability to flex its suspension, a property also known as axle articulation. The RTI rating is used mainly in the off-roading industry to test and describe chassis limits of modified vehicles....
and durability in a high load environment.
Beam axles are nonetheless common on low-cost, front-wheel drive
Front-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...
cars, particularly minivan
Minivan is a type of van designed for personal use. Minivans are typically either two-box or one box designs for maximum interior volume – and are taller than a sedan, hatchback, or a station wagon....
s and other vehicles placing a great emphasis on maximum internal volume.