The term "falling effect" is something that you see thrown around a lot in relation to progressive springs. The idea being that due to the softer initial spring rate the car rolls a lot more in the early stages of a corner and then as the springs stiffen up the roll is slowed / stopped. The car "falls" into the corner.
Now, this isn't something that I have ever really noticed on my car, or perhaps I just never identified it properly (Eibach Prokits currently, previously Tien S-Techs). What I have noticed is a feeling of what I will call "roll instability". The car seems to roll too far, and then once it gets there never really feel solid or like it has much grip to spare. Not very confidence inspiring, especially at higher speeds.
That was last year. This year, with roll center adjusters at all 4 corners, that feeling is totally gone. The car has very little body roll, takes a set in a corner perfectly, and feels like it has tons of grip. Very confidence inspiring indeed, and much more fun to drive.
The other day I remembered something I had read a while back, posted by a member in one of my other threads. I will relink it here:
http://www.neohio-scca.org/comp_clinic/hand_out_reprints/Mitchell Roll Center2007.pdf
The part that I was remembering I had quoted in my other thread, and will re quote here as well:
Wm. C. Mitchell said:
Stability results when the FAP-CG moment arm remains constant as the vehicle rolls. The chassis ?takes a set? rather than constantly seeking a new equilibrium. This can be expressed by minimizing the lateral movement of the KRC as the vehicle rolls. But this is an artifact: there are more direct ways to calculate this; namely with the change in FAP height resulting from ride. It should be one-to-one. (An easier way to visualize this is from the viewpoint of the chassis rather than the world. The FAP point should be constant as the wheels and tires move up and down.)
I am wondering, based both on that paragraph from the article and on my own experience, if the "falling effect" isn't caused by roll center movement more than, or at least as much as, by progressive springs.