Originally Posted by blackknight530i
I'm hoping Chuck (CSBM5) weighs in, because I've ridden in his M5 with the Dinan suspension and his looks fantastic. If I can find someone selling some Dinan springs, I may just go with those, but if someone can tell me the Eibachs are comparable, I may change to those instead.
Don't know if H&R have changed anything since, but 10+ years back the only springs available for the M5 from them were front springs. OldRanger did a nice job cutting the rears properly to balance things out on his car since otherwise the car sits seriously tail-high with those.
BTW, stock ride height is ~14.5" front, ~14.25 rear. Dinan spring spec is 14" +/- 0.25", but in my experience, most all end up more like 13.5-13.75" all around which is about where my car is.
I've had the Dinan springs for ~11 years now, and for street use only, they are a reasonable compromise. If the car had come with them, few owners would have complained imo. If I had to do it over again, I would go with GC coilovers and pick a nice firm spring rate (550/320 ish or thereabouts), since I don't mind a nice firm but supple ride (as in my M3 which is perfectly sprung/damped for my tastes).
For serious driving, the Dinan springs are way, way too soft. Here's a view of how much compliance they have under maximum cornering, braking and acceleration
. With GC camber plates set to max negative camber (-2.3), it's not "too bad" in such situations in terms of outright grip, but there's nonetheless a lot of movement and lack of tight body control in all transitions.