Originally Posted by red_fx444
do shackles cause spring fatigue over time? or does it not hurt the springs at all?
If you increase the center-to-center shackle length and do nothing else, it will raise the static height of the rear of the truck and increase the spring deflection when the suspension bottoms. If you are in situations where you use the truck hard off road or carry heavy loads in the bed, then the springs may fatigue and "sag" sooner. Longer shackles will have virtually no effect on the spring life of a truck that rarely or never bottoms its rear suspension.