Originally Posted by HP Autowerks
We have tried spring rates from 350 all the way up to 550 on the front of E9x non-M and M cars either for customers or during our Redline Time Attack days. 450F with the rebound damping cranked near all the way the front suspension is right near critical damping. The damper seems to be happiest with rates in the 350-450 range, not higher.
Was the SA on an E9x M car? Do you think the vehicle was at critical damping or slightly under damped? On SA kits, I don't recommend anything over 400F.
Yes, it was installed on an e92 M3. I played around with damping within a range of 0.5 to 1.5 turns from max (total range is 2.5 turns). The car felt well controlled at 0.5 turns (rear dampers were set between 0.5-0.75 turns) with 400/672 rates but my wife found the car to be "harsh" on expansion joints and bumps. At 1.5 turns the car obviously wasn't as well controlled but I certainly would not say it was underdamped; however, it made the wife happy! Just to be clear all of this was street driving, no track time.