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Originally Posted by gee-m-w
Compromised is a strong word. Even if it was only as strong as the E90 that would be more than adequate. The emphasis on efficiency, which is being achieved through lighter weight. This isn't about making the strongest M3 in the world. If they did, it would be 3800 pounds.
They built a fast attack boat, not a tank.
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Compromised is defined as:
"
To reduce the quality, value, or degree of something"
If BMW has weakened the chassis of the F8x over the F3x, then that would mean that they had compromised the structural stiffness of the chassis, right?
Some quotes/info taken from the official threads, since it seems you haven't taken the time to read them
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An aluminum stiffening plate, CFRP front strut brace and additional bolted joints between the axle subframe and the body structure all help to increase the rigidity of the front end.
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The rigid connection between the rear axle subframe and the body – without the use of elastic rubber elements – is borrowed from motor sport and serves to further improve wheel location and therefore directional stability. “The double-elastic mounting for the rear differential within the rear axle subframe – which is bolted to the body structure – has allowed us to achieve a new level of driving precision, but without neglecting comfort,” says Albert Biermann, citing another example of the perfect symbiosis of pure-bred motor sport technology and excellent everyday usability.
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“Together, the rigid front and rear structures, precise axle kinematics and an impressively responsive electromechanical power steering system help to deliver the outstanding steering and handling characteristics of the BMW M3 Sedan and BMW M4 Coupe,” sums up Biermann.
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On the outgoing models, the CFRP roof was confined to the Coupe version. Now, for the first time, the four-door BMW M3 will get this striking design and functional feature as well. The CFRP roof brings weight savings of five kilograms (11 lbs) in the case of the BMW M3 Sedan and more than six kilograms (> 13 lbs) in the case of the BMW M4 Coupe. It also lowers the vehicle’s center of gravity, which has a positive impact on driving dynamics.
Made from aluminum rather than conventional steel, the front side walls and the hood (with power dome) make an important contribution to the models’ lightweight design concept, while at the same time improving axle load distribution.
On the BMW M4 Coupe, the contoured roofline with central channel continues into the trunk lid, emphasizing the even sportier personality of the new model. The newly developed trunk lid not only provides extremely effective tail end styling, its geometry is at the same time precisely tailored for optimized aerodynamics, while the use of carbon fiber and plastics makes for additional weight savings.
The new BMW M3 Sedan and new BMW M4 Coupe also feature a CFRP propeller shaft. The high rigidity and low weight of the CFRP tube mean that the propeller shaft can be produced as a single-piece component, without a center bearing. This achieves weight savings of 40 percent over the previous model and a reduction in rotating masses, which in turn results in more dynamic powertrain response.
The CFRP strut brace in the engine compartment is a further example of how all weight-saving measures on these vehicles have also been tailored to the improvement of driving dynamics. Weighing only 1.5 kilograms (3.3 lbs), the strut brace offers superior rigidity to a comparable aluminum component and at the same time plays a key part in the excellent steering response and precision of both vehicles.
The use of carbon in these models is a reminder that BMW is a global leader in high-strength, lightweight CFRP construction, and that it was BMW who brought out the first mass-production vehicle with a body consisting entirely of this material – the innovative BMW i3.
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When I read the above, plus all of the other info available, there is NOTHING that indicates a less torsionally rigid version than the F3x. Quite contrary, everything points to added stiffness from strut brace, solid mounting of rear subframe etc.
Not sure I understand where your concern for the torsional rigidity of the F8x comes from
