public float getWheelsDampingCompression() {
        return wheelsDampingCompression;
    }
the damping coefficient for when the suspension is expanding.
See the comments for setWheelsDampingCompression for how to set k.

@param wheelsDampingRelaxation the desired damping coefficient
(default=2.3)
jme3-jbullet/src/main/java/com/jme3/bullet/objects/VehicleWheel.java