E46Fanatics - View Single Post - Concept for roll center correction. Fabricators and engineers please chime in.
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Old 10-02-2012, 05:37 PM   #50
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Join Date: Oct 2006
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Originally Posted by WDE46 View Post
I'm surprised nobody has posted a diagram of a MacPherson strut roll center. I took this from my vehicle dynamics textbook. It will help you visualize what can be done to lower the roll center.

From the diagram you can see that you can lower the roll center in several ways:

1. Lower ride height
2. Lower innder joint
3. raise outer joint
4. Increase shock lean towards outisde (more vertical from picture I believe)
5. increase track width
The significance of the roll center can only be appreciated when the vehicle's center of mass is also considered. If there is a difference between the position of the center of mass and the roll center a moment arm is created. When the vehicle experiences angular acceleration due to cornering, the size of the moment arm, combined with the stiffness of the springs and anti-roll bars (anti-sway bars in some parts of the world), dictates how much the vehicle will roll. This has other effects too, such as dynamic load transfer.
Lowering the roll center relative to the center of mass increases body roll and suspension compliance. We are trying to raise the roll center to correct it after lowering it when we lower our cars.

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