A spring shackle allows a leaf spring to flex and move while keeping the tire on the road. It can also increase vehicle ground clearance, but mounting the spring at maximum lift can cause the vehicle to sway and lose control. Certain designs incorporate a twist for off-road use.
A spring shackle is a device found on vehicles equipped with springs. It mounts to one end of the leaf spring and allows it to flex and move while keeping the tire on the road. Without a shackle, the spring would not be able to move and the tire would be pulled off the road surface when a bump or obstacle was encountered. The spring shackle can also be lengthened and give lift or increased vehicle ground clearance.
The leaf spring is attached at the front and rear by a long bolt that passes through the spring eyelet and a mounting bracket. One end of the spring is held close to the vehicle frame and cannot move, the other end of the spring has a spring shackle mounted between the frame bracket and the eye of the spring. This is nothing more than two flat pieces of steel with various holes drilled to allow for different mounting heights. Shackles allow movement of the suspension by pulling in or out as the suspension travels through its up and down cycle.
By choosing to mount the spring in the mounting hole furthest from the vehicle’s chassis, the spring is lowered and subsequently increases the vehicle’s ride height. While this does not increase the clearance between the vehicle’s axle and the ground, it does increase the amount of clearance between the vehicle’s fender and the tire. This increase allows more clearance when the body flexes on the chassis and allows the vehicle to traverse rougher terrain.
Certain spring shackle designs also incorporate a twist to allow the vehicle to rotate as the spring flexes. This type of spring shackle is generally used in severe off-road applications. This type of spring shackle can also incorporate a set of hinged shackles which, when fully deflected, open to give the shackle twice its length, resulting in twice the travel allowed by the spring.
The downside to running a leaf spring mounted at maximum lift on the road is that this allows the vehicle to sway on the springs. Leverage over a long period of time will start to pull and push the leaf spring until it becomes loose and neglected. This in turn will allow the chassis to sway on the springs and lose some of the control that was designed into the vehicle. While this sway may appear minor, it can have an adverse effect on vehicle handling in emergency turn situations.
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