[masraum]

Originally Posted by Schumi

For some reason, those pieces on the floor aren't quite screaming 'torsional rigidity' to me.

The book (various links on the page above) references Porsche several times.

http://www.kirkhammotorsports.com/book_aoe/aoe_03.pdf

They told me about the 1971–1972 Porsche 917 chassis that were made out of aluminum and prone to cracking failures. To predict the failures, Porsche welded Schrader valves into their chassis tubes and mounted a gauge onto another bung in the chassis. Before a race the team pressurized Chassis components are doweled together—like an engine’s connecting rod. The bolt then passes through the dowel.
the chassis with air; every time the car came into a pit stop, they checked the pressure gauge. If the chassis lost pressure, they knew they had a fatigue crack somewhere in the chassis. Porsche engineers are very bright; if they thought aluminum could save them weight, then I reasoned I should be able to use it as well.

By analyzing an original chassis, we discovered the original 427 Cobra chassis had a stiffness of 1450 foot pounds/degree of deflection. Analysis of the billet aluminum chassis showed a stiffness of close to 4500 foot pounds/degree of deflection, or a 300% improvement over an original chassis (actual stiffness is a little lower because we did not perfectly model the bolted-together joints).

I find it interesting that they talk about Porsche in the "Chapter 11: Half Shafts" section too.