Roll Axis The roll axis is the line that would connect the roll centre at the front axle to roll centre at the rear axle. Building on the fact that front and rear roll centres will not always be at the same point at the front or rear of the vehicle, the roll axis will usually not be parallel to the ground plane. (Smith, 1978, p29) Roll Moment Also visualised on figure 2.1, the roll moment is the distance between the centre of gravity at the transverse plane defined by the axle, and the roll centre. In order to calculate the roll moment for the vehicle as a whole and not just either axle location, it is required to find the transverse plane that the overall centre of gravity of the car is located in and then at this cross section, determine the distance between the mass centroid axis and the roll axis. The relation of all these parameters can be observed over the page on figure 2.2 (Smith, 1978, p30) Figure 2.1: Determination of roll centre and moment arm. (Smith, 1978, p30) 15 Dynamic Load Transfer According the Carroll Smith (1978, p31), dynamic load transfer “is the load transferred from one wheel to another due to the moments about the vehicle’s center of gravity or its roll centers as the vehicle is accelerated in one sense or another.” Longitudinal Load Transfer Longitudinal load transfer is the result of the cars mass accelerating from the front of the vehicle to the back or the back to the front under accelerating or braking respectively. It is important to mention that “The total weight of the vehicle does not change; load is merely transferred from the wheels at one end of the car to the wheels at the other end” (Smith, 1978, p29). The amount of load transfer that occurs is governed by the following formula which is also detailed by Carroll Smith: