Originally Posted by tibra1
Has anyone considered that that the M5's entire suspension was designed to incorporate a solid subframe such as this..trying to apply a 1 to 1 ...to the M3 would not be optimal ..completely apples and oranges
I couldn't disagree more in this regard.
BMW like any other great company learns and progresses over time. They learn from previous designs and their implications.
There is no harm in changing the rubber sub-frame bushings to solid. By harm, I am referring to physical harm to the vehicles chassis and its dynamics. I am not referring to harm caused in potential ride comfort reduction (which is extremely subjective in most cases).
A rigid sub-frame reduces, if not prevents sub-frame and in worse cases, uni-body damage (as evident in E36 and E46 cars).
If one was to unitize other parts, such as the differential to the axle carrier, yes other work will need to be done, such as reinforcement to the mounting brackets and tabs. It is not true that if you unitize the differential it will prevent this, the load and shock of the differential are now being transferred to the next weakest link, the differential mounts themselves.
If you undo the sub-frame out of the E9x M3, you will see how unimpressive the differential mounts are. Changing these bushings will now reduce the failure of hardware and the actual bushing at the cost of the mounts. Energy is never lost, only transferred.