Steering & Suspension: Suspension Systems: Types of suspension
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Topic IntroductionHelp

Dead axle

Summary
A dead axle only supports the vehicle and doesn't transmit any drive. With a live axle, the drive is transmitted through the final drive unit and axles to the wheels.

On front-wheel-drive vehicles, a simple beam axle can be used on the rear, with coil spring suspension and control arms for location. This is called a dead axle, since it only supports the vehicle and doesn’t transmit any drive. It is also non-independent, as deflection of a wheel on one side of the vehicle will be transferred to the other wheel.

On some vehicles, this is reduced by using a U-shaped axle beam, with a torsion bar mounted inside it.

Trailing arms are welded to the beam, to locate the axle longitudinally.

A lateral rod prevents lateral movement when cornering, and coil springs provide for suspension. The torsion bar is connected between the left and right wheel units, and deflection of the wheel on one side causes the axle and its torsion bar to twist together.

Passenger cars no longer use beam axle front suspension, but it is still common on heavy commercial vehicles, and some 4-wheel-drives.

Trucks use an I-beam, in most cases located by leaf springs.

4-wheel-drives, with rigid axles, may use leaf springs for front and rear suspension.

Coil springs may also be used for front and rear, and as with other beam axle designs, control arms and a lateral rod must be used for location.