Luis,

I agree with you.
Body roll is a result of weight transfer.

It is purely semantic; The "body roll" in the formula should be called "roll stiffness" to avoid confusion.

Let me rewrite them:

The higher roll stiffness will get higher portion of weight tranfer. Therefore, stiffer front will make more understeer.
Sway bar stiffness and spring rates adjust the proportion of front/rear weight transfer.

1) Total lateral weight transfer = Weight Transfer(WT) due to roll stiffness + WT due to roll center heights + WT due to unsprung weight.

2) Front Weight Transfer due to roll stiffness = Front roll couple/Front track width
Rear Weight Transfer due to roll stiffness = Rear roll couple/Rear track width
The total of WT due to body roll is the sum of both.

3) Front roll couple = Front roll stiffness/total roll stiffness * Total roll couple

 

Luis... Please just think about this one. Lets use the case you supplied where you corner so hard that the outside bottoms out. YES - the outside effectively now has an infinite spring rate and can go no lower. BUT, if you consider that the other side has a spring pushing it UP, the stiffer the spring, the farther it will push up, the more total body roll you will have. I'm tired and I think I explained it better in the previous posts, but maybe this will be clearer to you for whatever reason.

 

Reading closer, I still do not understand what that has to do with "stiffer springs inducing more roll". If a stiffer spring is compressed to its max, a softer one would have been compressed to the max as well. Just more often.

On top of that if a spring bottoms out, it effectively becomes a much stiffer spring and roll is thus reduced.

[/B][/QUOTE]

A spring that bottoms out effectivly changes roll point and that combined with wherever the center of gravity is can allow the other spring to lift the other side. Like I said there are too many variables to account for, you need a precise situation to be certain. You cant just say yea or nay.

 

[QUOTE]Originally posted by The Reverend
[B]Luis...

 

when a spring bottoms out and changes the roll point, depending on where the center of gravity is, therby changes how much effort the inside spring has to exert to lift that side. You also have to figure in how much the springs will compress and/or extend within the travel range. Usually with a modified car, the wheels can go down in relation the the body, more than they can go up.

Also not all spring rates are exactly liniar within extension range. Also the force realized by the sus. is not an equal transfer. If 100kg comes off of the inside there may be even more force than 100kg added to the outside.

Go stand on a scale, then jump. Your weight didnt change but the scale and springs inside realized a much greater force.

 

[QUOTE]Originally posted by cmnsnse
[B]Go stand on a scale, then jump. Your weight didnt change but the scale and springs inside realized a much greater force.

 

Better yet, go stand on two scales, note the readings, make sure they are about equal, and jump to one side. (make sure they dontmove)

You will get a much greater reading on one side than came off the other.

 

OK so you understand that wieght changes unevenly?

So that means that one side can realize more than the other is releived of? Then why cant a spring bottom out while the other still has room/force to extend?

 

And yes Luis you are right about weight/mass . .

Pardon my mis-use of terminology, but that wasnt the issue.

 

Luis, it's been a while since I took a physics class, but I was a hell of a physics student in college. I don't remember all the terminology, but I remember the general principles. Yes, you have outdone cmnsense and I on semantics, but you seem to have missed our point. As you pointed out, the mass does not change, but when you rip a corner at close to 1 lateral g, the weight on each wheel does not necessarily add up to what it adds up to at rest. And like cmnsense pointed out, you'd be hard pressed to find a spring with a truly linear rate of resistance as it is compressed. Anyway, if you don't believe me, next time you're in the US, stop by and I'll take you for a ride in my car and you can see for yourself a car with stiffer springs and increased body roll. I promise you I'm not making this up.