The leaf spring is one of the oldest forms of springing. It is usually used on rear-wheel-drive vehicles because its simplicity.
They can be mounted longitudinally.
Leaf springs consist of one or more flat springs, made of tempered steel. A number of leaves of different length are used to form a multi-leaf spring.
They are held together by a center bolt that passes through a hole in the center of each leaf. It is also used to locate the axle on the spring. The axle is then clamped to the spring by U-bolts that wrap around the axle housing, and through a spring plate underneath the spring.
Rebound clips are formed at intervals around the leaves. They prevent excessive flexing of the main leaf during rebound, and also keep the leaves in alignment.
The longest leaf called the main leaf, is rolled at both ends to form eyes. These eyes are used to mount the spring to the frame of the vehicle.
Some springs have the ends of the second leaf rolled around the eyes of the main leaf, as reinforcement. This leaf is called the wrap leaf.
The front of the spring is attached to a rigid spring hanger on the vehicle frame.
The rear is connected to the frame by a swinging shackle, which provides a link between the spring eye and a bracket on the subframe.
This swinging link is needed, because, as the spring flexes, and flattens out under load, the distance between the spring eyes increases.
Some springs have inserts between the leaves, of plastic, nylon, or rubber. They act as insulators, to reduce noise transfer, and friction as the leaves move under load.
Some older vehicles completely enclose the leaf springs in grease.
The spring eyes are fitted with bushes, usually with a rubber, flexible section, but nylon and urethane bushes are also used, and sometimes bronze for heavy duty applications.
Rubber insulating pads between the spring mounting pad and the spring also act as insulators.
And similarly, between the spring plate and the spring.
The spring forms a flexible suspension unit that locates the axle housing longitudinally and laterally.
It can sustain the torque reaction on acceleration and the braking torque during deceleration, and the driving thrust is transferred through the front half of the spring to the fixed shackle point.