BUTTERS SS

Installed a Belltech 2/2 (spindles and shackles). Front seems great after the allignment, but the rear has alot of vibration around 70+mph. Thinking that I need to get some shims, how do I calculate the shim needed, or is it trial and error?

Thanks for clearing that up, makes perfect sense now. I feel pretty dumb for asking, . I was thinking all backwards.

I am planning on installing some spindles and shackles this weekend. After reading the "how to" on installing rear shackles and hangers, it stated to leave the spring bolts loose until after the truck is on the ground, and working the springs through their range of motion before tightening. And in the belltech manual it suggests that you lift the truck with a floor jack until it 's weight is off of the jack stands then to tighten the hardware before lowering it to the ground. Just curious what meathod you guys have had success with?