On these rigs, the upper carries the weight of the rig and the weight of the tire when the suspension tops out on droop. The lower supports the rig when the suspension bottoms out and gets the damping forces from the shock.

On the newer IFS, the lower BJ gets all the abuse and the upper just locates the top of the knuckle.


'97 4Runner, '06 F350, '86 4Runner, '05 WR450
http://home.4x4wire.com/erik