High chassis stiffness is desireable, and overall chassis stiffness is usually expressed as the frequency of the first bending or torsional vibration mode, and 25 Hz is considered a good target. Mercedes have probably been stiffer than most cars up to at least the nineties, but the industry is catching up. The key is to increase stiffness without adding excess weight and this is possible with ever more sophisticated structural analysis software.

Back in the early nineties my car developed a creak in the right rear C-pillar, which was noticeable when the body was stressed in torsion like entering a driveway at an angle.

The dealer fixed the problem under warranty, but they never gave me an adequate explaination of what they did.

Duke