[Shipkiller]

Originally Posted by funkle

I imagine it's pretty moot at sub 30mph speeds, where an airbag wouldn't even deploy.

There is no low end set point (speed) for not deploying an air bag on the Z4. The Advanced Safety Electronics (ASE) system decides what to do based on a number of factors and assigns a Crash Severity (CS) number plus other factors in determining what to do.

Airbag Triggering
Numerous crash and road tests under extreme conditions have been used to set the BMW triggering thresholds for all possible types of accidents.
The triggering thresholds are primarily divided into 4 groups according to crash severity:

CS 0: no crash (parking damage) CS=Crash Severity
CS 1: light crash
CS 2: crash of medium severity
CS 3: severe crash

The triggering thresholds have been set depending on the crash severity and including other factors such as direction, overlap on collision, and depending on the evaluation as to whether the occupant was wearing a seatbelt or not.

This results in the various trigger thresholds for the activation of the various restraint systems.

There is more info on this subject. Just do not get locked into believing the 30mph number.