Lesson 3/Learning Event 1
The shackle allows the springs to flex as the weight of the vehicle load is changed and as
the vehicle travels over rough roads. Flexing of a spring causes its length to change. The
flexing action of the laminated leaf-type spring is restricted by the friction of the leaves
There are several different types of spring shackles. The bolt-type shackle has two flat
sidepieces. The pins are made like bolts, with a head on one end and threads on the other
end to receive a nut. It has a grease fitting and passages that permit lubrication to the
center of the bearing.
In the straight, threaded-type shackle, the bearings have internal threads. Threaded pins
are then screwed into each bearing. The ends of the pins are fitted into holes in the
shackle sidepieces. Bolts or small pins are placed in holes in the sidepieces, engaging
grooves cut in the threaded pins. This holds the sidepieces on the threaded pins.
The U-type shackle is a one-piece, U-shaped bolt that is threaded on both ends. The
bearings are threaded both internally and externally. To assemble the U-type shackle, the
shackle must first be placed inside the bearing bores of the spring and spring hanger. The
threaded bearing is then screwed into the bearing bore and onto the shackle at the same
The pin-and-bolt-type shackle usually has a one-piece shackle that resembles the letter
"H." The shackle is fastened to the spring and spring hanger by straight pins. The pins
are locked in place by bolts as on the straight, threaded-type shackle.
The center-bolt-type shackle consists of two sidepieces, a center bolt, and two threaded
pins tapered on their ends. The bearings are threaded on the inside to receive the
threaded pins. The shackle sidepieces have tapered holes that fit over the tapered ends of
the pins. The center bolt passes through the sidepieces and holds them tight on the tapers.
In a variation of this shackle, the pins have a threaded portion extending beyond the
tapers. Nuts and washers are then used to secure the sidepieces instead of the center bolt.
The single-piece link shackle has a one-piece U-shaped shackle that forms both
sidepieces. Bolt-type pins secure the shackle to the spring and spring hanger.
The Y-shackle is a one-piece shackle that has the shape of the letter "Y." One of the
bearings is contained in the shackle itself.