Originally Posted by Razathorn

That's not showing the center of gravity is at 24mm. When you raise the car up, the center of gravity goes up too, so that's a bit chicken/egg. I believe what you have encountered is you raised your ride height such that you raised your roll center above ground and now jacking force has reversed. What you have demonstrated was raising the front roll center above ground and its affect on jacking forces.

A more accurate jacking force demonstration of jacking force would be to press at the base of the tires near the contact patch.

Jacking forces are the upward or downward force placed against the chassis due to roll action and chassis geometry. If the roll center is above ground, the jacking forces will raise the chassis. If the roll center is below ground, the jacking forces will suck the car toward the ground.

The b44 platform places the roll center really low due to its nominal ride height, If you try this on a b4 rear, it will actually raise at 24mm ride height, but the center of gravity is well above 24mm on the b4.

Jacking forces are one of those things you rarely consider outside of the initial design of the car. Front roll centers are frequently found below ground and tend to suck the front down and add steering on hard corners. Rear roll centers are frequently found slightly above ground, allowing making the rear suck down on hard corner exit when weight transfer lowers the rear and reverses the jacking forces, while still allowing the rear to unload easily in corner entry. The relative GENERAL location of roll centers are part of the car's design. The final fine tuning position achieved with camber link positions and ball stud washers is just playing in that area.

This is yet another reason one does not vary ride height much from the factory settings -- it jacks up the jacking forces and general location the roll centers should be for the car to behave right in all situations.

Wayne