Originally Posted by ebohon
Thanks! That makes more sense. I have Eibachs on my Lexus IS now and I agree about the effect. With the old springs, the car seemed to roll quiet a bit. I think Eibach builds their springs progressive (non-linear???) with a bit of softness on the first fraction of compression and quickly stiffens IMO for spirited driving. Ed.
Yes, that's what it is... but it seems that in this E9x M3 ProKit version only the front springs are progressive and the rears are linear.