I gave it a race car treatment to address one of my concerns - a softer chassis compared to other fellow C36s and the later year W202s (1998 and onwards). In a nutshell it is a chassis stiffening to the passenger compartment. PU components are poured into the hollow side sills and beam sections left and right just underneath the 4 doors. I am happy to report a positive result overall. The PU will expand rapidly and eagerly to any hollowness it can find, it will then hardern and expand a little more, providing pressure to its exoskeleton against the inner surface of the steel sections.
The ride does change for the overall good. The car will wiggle a bit more in most road surface other than the ultra smooth one. It does not constitute a nervous ride by all means and reduce comfort or refinement. However that's how modern BMW and Mercedes sports cars behave as well. Bump thumps are slightly more damped and yet shift in frequency and change in the way they are felt. I found the improvement acceptable if not completely satisfied. It is indeed a better balanced ride I was looking for, even though it was not exactly what I had anticipated.
The steering effort has increased for no obvious reason, especially in slow speed maneuvers. In a few hundred kms when the tires are starting to get used to the new contact patches and I will report again. The car does feel lighter and more responsive. It will turn in cleaner and hold cornering load and track cornering line in a more steady and flatter manner. It does not change what C36 originally is, nor redefine for what it is. I like that because I only want it to have a incremental and yet controlled improvement for what is good for me originally.
For those who wonder what the treatment is, see the link below.
http://www.junauto.co.jp/products/reinforcement/polyurethane-foam-kit/index.html?en
