Shackles are used to position the torsion arm at the correct angle for the correct progressive spring rate. Torsion arm angle is a function of shackle length in combination with bearing carrier plate hole location. Approximately 1″ or 1-1/4″ difference in length between the left rear shackle and the right rear shackle is recommended for proper torsion arm angle with the left rear being longer.
Our black anodized shackle rods are available in 2″, 2.5″, 3″, 3.5″ and 4″ lengths. If purchasing just the rod, pick up the corresponding rod ends and jam nuts: 71-CML7 (1), 71-CMR7 (1), 70-325 (1) and 70-326 (1). Complete shackle assemblies which include the rod ends and jam nuts are also available.
On the X4 and X6 style bearing carriers, the right rear is typically just a female and male rod end threaded together making a 3-1/4″ center to center shackle and the left rear is a 2″ shackle rod making a 4″ center to center shackle with the rod ends screwed in.
On the X7 style bearing carriers, longer shackles are needed. We recommend using a 3″ (just the length of the shackle itself with no rods end in it) on the right rear and a 4″ on the left rear. Use the 40-400 Torsion Arm Standoff to allow proper shock travel, because without it, the shocks will not allow the chassis to get high enough and the shocks will top out. Start with the shackle mounted in the middle hole of the X7 bearing carrier plate.
Why Longer Shackles? Front to back shackle angle has an effect on spring rate. A greater angle equates to less spring rate. The X7 shackles are longer allowing for greater front to back misalignment between the torsion arm and the bearing carrier with minimal angle change to the shackle. This reduction in angle equates to a more consistent handling chassis.
Recommended Shackle Rod Lengths Measurements:
Below measurements refer to shackle rod lengths before adding the rod ends.
• X7 wingless right rear: 2.5” rod, total length of 4.5″
• X7 wingless left rear: 3.5” rod, total length of 5.5″
• X7 winged right rear: 3” rod, total length of 5″
• X7 winged Left rear (dry slick): 4” rod, total length of 6”
• X4-X6 left rear: 2”, total length of 4”*
*To make the correct length of 4″, cut 1/4″ off each rod end to allow them to thread in far enough.