I completely understand all of the theory. As an engineer, I'm also not willing to assume that the performance of a spring designed for one application is going to be representative of all springs from a given manufacturer. I'm also not implying that the Swift springs aren't great springs, just trying to get beyond the marketing pitch to determine how much practical difference they really make versus other "same rate" springs in a BMW application. Stating that you could really feel a difference between 2 sets of springs of different rates and brands is meaningless. If you changed the rates, of course you're going to feel a difference, doesn't matter the brand. When you guys state that you can really feel a difference, what exactly does that mean? How does that translate into grip over rough pavement, transient response, lap times, etc?
"Better" is always a good thing but would you really notice a difference if one brand of chocolate chip cookie contained one more chocolate chip than it's nearest competitor? Sure you could count the chips and see that it was better but would you actually taste a difference?
04 IR 330i ZHP | ESS TS2+ SC | MagnaFlow "headers" | KMS 3.64 LSD | AST 4100 550/650| APEX ARC-8 18x9 | H&R front sway bar | Vorshlag camber plates, RTAB limiters | TMS subframe & swaybar reinforcements | UUC SSK & DSSR | UUC TM & TME | BW motor mounts | Dinan strut & shock tower bars | vaio 4-bolt oil pump