Outstanding article.
One thing to remember is that the forces acting upon a vehicle also include those due to acceleration or deceleration in addition to gravity and friction.
So if you are in a situation where you are stable on a hill in a static condition, that is to say your center of gravity is within the rectangle described by the projection of your wheelbase onto a horizontal plane, you will be in a no rollover condition.
However, you can be on that same hill and be going down it, for example, at the same angle, and then, for example, slam on the brakes. This has the effect of moving your "center of gravity" forward with respect to the horzontal projection of your wheelbase, and could cause the center of gravity to move forward of your front tire patch and throw you into a endo.
Technically, the center of MASS does not move forward, but the center of FORCE does, and the article talks about the center of gravity, which
is the center of force in a static condition but not in a condition of acceleration or deceleration. So if braking, acceleration or spring bounce cause your center of force to move out of the rectangle, you will be in a roll condition, even if your center of mass is within the rectangle.
So in other words if you do all the measurements and calculations and come up with numbers for your rollover angles, an additional margin has to be added to allow for the
dynamic conditions associated with braking, acceleration, and spring bounce. ALso there is the error introduced by forces associated with gasoline sloshing and passenger overexcitement.
