I've been searching the archives for info about larger tires and lift kits. One of the more popular methods to lift the XTerra seems to be to put 2" SLR shackles on the rear. But everyone says that the rear leafs will start to sag.

Why is this? How do the shackles put more stress on the springs? Does it do this even with new rear shocks? Are the stock springs just cheap? Will the springs eventually sag even without the lift?

Thanks,
Greg

All springs sag, no matter what type of vehicle they are on, metal just fatigues over time and during use.

Longer shackles won't make springs sag any faster than the stock length shackles, it is just a myth.

The spring has no idea how it is attached to the frame, and a longer shackle allows the spring to move through it's travel no different than the stock length shackle.