Jacking is the vertical force generated at a wheel by the suspension linkage during cornering, which acts to raise or lower the sprung mass rather than to resist lateral load. It occurs because lateral force at the contact patch is reacted along a line through the instant center, and any vertical component of that line is fed into the chassis as a lifting or lowering force. The height of the roll center relative to the ground sets its magnitude and direction, so a roll center above ground level pushes the sprung mass up in a corner and one below ground pulls it down. Jacking is the main reason a high roll center is not simply an easy way to reduce body roll: it raises the center of gravity in the corner and changes the suspension geometry away from the position it was set up in, which is why roll center height is managed rather than maximized.