Quote:
Originally Posted by aerobod
They seem to have done a lot of analysis on the rear spring rates with plausible results, but the rates for the front that were thrown out are highly suspect, a lot less than expected and would lead to handling problems if only 1/3 or 1/4 the rate of the rear. They also don't take into account any variable rate effect as the coils bind or the bump stops are reached.
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You're right - there is less data on that thread about front rates than rear rates, and they don't mention the other factors you've highlight above. Seeing as no-one else (at least not yet found on this forum) has done the work to calculate, the rate estimates on that thread are about as good as you'll find anywhere though. Also, the OEM F80/F82 front spring rates aren't very stiff either.
Reading the below thread you'll find the F80/F82 crowd as well as the engineers at Swift Springs would disagree with you about the handling characteristics of high spring rate variances between front and rear on F-Series bmws. In addition, the AFE Control Coilovers for F30s (couldn't find any reviews on these) have an even higher front rear variance than the Swift Springs! Not trying to argue here, just suggesting the data seems to go against your intuition on this and maybe the front rate estimates on babybmw aren't too far off.
https://f80.bimmerpost.com/forums/sh....php?t=1054041
185 lb/in Stock M3/4 Front Springs
575 lb/in Stock M3/4 Rear Springs
268 lb/in M3 Swift Spec-R Front Springs
715 lb/in M3 Swift Spec-R Rear Springs
279 lb/in M4 Swift Spec-R Front Springs
726 lb/in M4 Swift Spec-R Rear Springs
https://afepower.com/afe-power-430-5...oilover-system
275 lbs/in Front, 1100 lbs/in rear