[Number 3]

First, I can't quote the numbers but Mustang convertible is a limp noodle compared to the Camaro convertible. The team did a truly outstanding job in getting it right.

If anyone remember the C4 Corvette Targa roof..................bolted in with a wrench in the console. You could tell a huge difference with a targa in and out let alone a convertible.

The big issue, as Lowdown points out, is "cowl shake". Going over railroad tracks in a vert is a real tell on the structure of a car. If the wheel feels solid you have a winner. But the Gen 4 Camaro was a joke in relative terms for that test.

As for stiffness, you can do a simple calculation on the stiffness of a car or truck. The two usually considered are bending and torsion. Bending is simply holding the bumpers fixed and pushing up or down in the center of the body. Torsion is simply holding one bumper fixed and twisting the other.

Torsional stiffness can be in Nm/degree or torque applied per resulting twist. This gives you the simple stiffness in twist. A good number, but not always the whole story.

A stiffer car allows for some more precise suspension tuning. For example, a car that is less stiff needs all kinds of sway bars and stiff springs to handle really well. Both of these can be counter to a car that rides well. You somewhat have to consider the loose structure as part of the suspension. But stiffen the body up and you can now use the suspension and tires more appropriately. An entire engineering class or two in that, but that is the jist of it.

Now for the other part of the story, and maybe more important for a street car, is the modal ananlysis or frequency. It isn't quite sound waves, but simply you can put an accelerometer on any beam and whack it with a hammer. From the input and the resulting output you can determine the first mode. That is the frequency where the object would go into resonance. Now if you applied the sound at that frequency you could get the beam to go into resonance. I believe this is how you get the crystal glass to break with a tuning fork or in Lexus case with an LFX exhaust.

The modes are related to the simple bending and torsional measurements for stiffness, but you will have modal targets set simply to make sure that the body structure of the car does not have a first (or second or third etc. for that matter) mode that can be excited by road inputs. If I recall correctly, and I've stated many times before that is dangerous, "most" roads will go up to about 13 Hz. So you need to make sure the first mode is higher than that so that the road input doesn't excite the body close to it's resonant frequency. Again another one or two engineering classes in that.

A car that is very high in stiffness and frequency is generally one that "feels" more solid when driving not just on smooth pavement, but as Lowdown points out, belgian blocks (a key GM road input at the proving grounds).

And overall, body stiffness goes hand in hand with chassis tuning and tire selection. A huge puzzle to solve which is why it can take so long to get you an truly outstanding Camaro (or any other great car for that matter).

There let the questioning begin.