Leaf spring suspension

The leaf spring is the oldest vehicle suspension still in production and the standard rear suspension of Indian trucks, pickups and vans such as the Tata Ace, Mahindra Bolero, Ashok Leyland Dost and Isuzu D-Max. A spring is a stack of curved spring-steel strips, the longest main leaf on top with shorter helper leaves below, held together by a centre bolt and rebound clips. The pack is clamped to the axle by two U-bolts. Its front eye is pinned to a fixed hanger on the chassis rail; its rear eye hangs from a shackle, a short swinging link.

• Load or a bump pushes the axle up towards the chassis and the arched pack flattens.
• As it flattens the spring gets longer, so the shackle swings backward to let the rear eye move.
• The leaves slide over one another and the friction between them absorbs some of the energy; a separate damper does the rest.
• The pack springs back to its arch and the shackle swings forward again.
• The stiff pack also stops the axle moving sideways or twisting under drive and braking forces.

Because the spring both carries the load and locates the axle, no control arms, bushes or anti-roll bar are needed, which keeps a commercial vehicle cheap and easy to repair with simple tools anywhere in the country. The driver notices a stiff, bouncy ride when the vehicle is empty, settling into a comfortable one when fully loaded, and the occasional creak from dry leaves. Overloading permanently flattens the arch, so a sagging rear end is a common sight on hard-worked trucks.