top shotta: Yeah no joke. It's hard to talk about roll centers without being general in many areas leading to even more questions. The fact that there is (as with everything) no one right answer only makes things worse.

As far as watching the suspension moving up and down, you aren't watching to see if one end bottoms out or not. You aren't trying to make them bottom out at the same time. You are merely trying to make each end move up and down at the same rate. If they are off, such as the front end bouncing up and down at a faster rate than the rear, you've got an imbalance. The rate at which is bounces up and down is the suspension frequency and each end has one. We want them to be the same or nearly so.

To paint a mental picture, let's say we have a booming stereo system. Let's say we have 2 big 15" subs playing a 30 hz note. The actual frequency doesn't matter but the point is that we have each sub going back and forth. We can see this. If they are each playing 30 hz, they are the same, correct? Now what happens if we change the signal to one of them and now one is playing 30 hz and the other is playing 40 hz. Is it still the same? Of course not. The cones even move at different rates. One goes back and forth 30 times per second and the other 40. This is what we are balancing with springs. We want both to play the same frequency.

Now in regards to the rear of the car bouncing more than the front, from the above example we agree that each speaker playing the same frequency is balanced. It's obvious that it's the same. They are moving in and out at exactly the same rate. What if one speaker is playing 30 hz at 125 decibels but the other speaker is playing 30 hz at a much lower level, say 50 decibels? Are the still playing the same frequency? Of course they are. They are just doing it at a different intensity level. There is more energy going to one than the other. On the XXX video (that sounds bad!) there is far more weight in the rear of the car and hence more energy going back and forth. For all intents and purposes the rear is playing louder than the front but they are playing the same frequency.

Hopefully that example works and makes things a bit more clear and for god's sake please don't try to pick technical holes in the analogy. I'm just trying to get a mental picture going, not write a technical manual for an engineering college.