Originally Posted by Mister Two

The progressive rate means the spring is divided into two sections. the top section has a lower rate and the bottom section has a higher rate. That way, when you just cruising along and you hit bumps and stuff in the road, you dont get a spine shattering jolt through the car and the spring absorbs the bumb and the ride comfort is good. But having the stiffer lower section means that when you corner, the upper section compresses completely and the lower stiffer section takes over and you get excellent control through corners with out getting heaps of body roll.

The only bad thing about the whiteline progressive rates, is that when you go over a speed bump a little too fast the springs will "clunk" a little bit. Its not a bad thing, its just the top part of the spring compressing and the coils are touching each other.