[Watsey]

There's lots to consider when changing suspension components, i.e. springs and dampers. If bump stops are taking frequent load/impact then something isn't right.

A shorter spring may provide the desired drop but the spring rate needs to be higher to offset the shorter operating range. Most good quality aftermarket springs have a higher rate, but, it needs to be sufficient for the damper pistons to be kept in their designed operating range relative to the damper body so as to avoid the risk of damper pistons bottoming-out inside the dampers. Big drops + OEM dampers can = trouble.

BMW OEM dampers are a real weak point and can struggle to arrest the momentum of the chassis which then brings the bump stops into play, but, we really shouldn't be relying on bump stops as part of a suspension setup except to help prevent damage.

Prior to having Ohlins R&T fitted to my car it was running OEM dampers and AC Schnitzer springs. The rear bump stops were removed (Ohlins R&T has internal bump stops) and we could have a good look at them. I'd always felt that the ACS rear springs were too soft for the F31, and this was evidenced by the stops - they were shot (split at one of the narrower parts of the stop).