Heave

Heave Motion is when the vehicle’s chassis moves vertically. Positive heave is when the chassis lifts. Negative heave is when the chassis drops.

The Heave motion comprises of both the front and rear suspension linkages undergoing bump or droop simultaneously. This means that chassis does not undergo roll or pitch motions. Depending on the nature of the suspension geometry, heave motion can induce track and wheelbase changes.

Image 1 shows the chassis at the neutral position, with the roll axis parallel to the vehicle longitudinal axis. With Image 2, the chassis is subjected to 2.5° of pure roll, and the roll axis is observed to have shifted.

With Image 3 however, an initial heave motion of -10mm was included prior to the roll motion, and the roll axis is observed to have skewed further. This highlights the importance of including heave motions in the calculation.