Originally Posted by FordX4Ranger
I have been running the belltech shackles for about a year now and was wondering if they could cause the leafs to go flat.
Yes. With longer than stock shackles, the springs can flex more before they hit the bump stops. It's similar to torsion bars that "sag" prematurely after being cranked. In both cases, the springs are being allowed to deform beyond the original design intent.
All automotive springs tend to change shape over time even in the stock configuration. Modifications that allow bending or twisting to a greater degree will simply accelerate that process.