Originally Posted by
thebomber
Newbie here and very interested in this conversation. Am I close to understanding if I believe the following to be true?
Center of Mass (COM) is the point where you would have to hold the car to have it balance on a single point. By adjusting the ride height, you are not changing the COM only it's position relative to the ground. The higher the ride height the greater the distance between the COM and the contact patch with the gound. This creates a longer moment arm (leverage) increasing the rotational and/or sliding force. Makes it top heavy if you will.
The center of mass/gravity at each end is what is important for roll center and connecting moment arm.
The roll center is point at which the chassis rolls about. For the sake of arguement it's the physical center of a ball. If you push the ball at it's physical center it will not roll but move linearly away from the force (neglecting friction). If I push the ball above the center, it will roll away from me. If I push the ball below the center, it will roll towards me.
Does that make sense or can you clarify?
Well, the ball is a bad example. The "roll center" of a ball is where it contacts the ground. The "roll center" of any simple object is where it contacts the ground. It's not in the center of mass.
What we were talking about was jacking forces, which you honestly don't need to even think about outside of designing a new car or making radical changes, to which I assume you are not planning.
In regard to the roll center and its relation to the center of mass at a given end, simply think of the roll center as a virtual point that does not exist but is effectively where hand is at, holding a broom with a big head. The broom stick is the moment arm. Longer the broom stick, the harder it is for you to keep that broom head from swaying back and forth (more roll). The shorter, the easier to control (less roll). The lower the roll center, the lower your hand, since the center of mass (broom head) does not change. So, a lower roll center makes the moment arm (broom stick exposed) longer, and thus it more readily sways (roll).
Hope that helps.