The solid or beam axle provides a simple means of locating and mounting the hub and wheel units. Together with leaf springs, it forms an effective, non-independent suspension system.
Similarly, with coil springs.
It is still used in the rear suspension of many front-engined, rear-wheel-drive cars, and light commercial vehicles, and as the front suspension on many heavy commercial vehicles.
On rear-wheel-drive vehicles, with leaf springs, the axle housing is held in place by the springs, and no other form of location is needed.
The drive is transmitted through the final drive unit and axles to the wheels, and therefore the axle is referred to as a live axle.
When a vehicle accelerates from rest, the resistance of its mass causes a torque reaction, producing a tendency for the axle housing to rotate in the direction that is opposite to wheel rotation.
A similar effect occurs during braking, but with the twisting effect in the direction of wheel rotation.
In both cases, this tendency can cause leaf spring wind-up, and the twisting action can interfere with suspension motion.
It is usually controlled by mounting the axle housing closer to the fixed shackle point, so that the spring’s front section is shorter than the rear section. The short, stiff front section resists twisting, and a bump-stop above the final drive housing can also be used to restrict upward motion during acceleration.
