Originally Posted by RPM90
If this kit's springs are like the other BMW models M Perf kit, then the springs rates are a good bit firmer and should be quite noticeable.
I believe the rate increase is like 48% firmer than the standard suspension and 34% firmer than the sport suspension, that's a good bit firmer. Plus, as you note, they lower the car by 10mm lower than the sport suspension.
I'd like to try those springs with my adaptive dampers.
I am just guessing based on the ride from the E9x performance suspension.
Yes it is firmer, but it doesn't feel like the ride is ruined or something. And since the F3x has such an improved ride over the E9x I think the ride will still be just fine for most people.
But I might not the best judge of what is acceptable since I'm running 20's with ultra low profile and soon coilovers on top of that