The Approach angle calculator computes the maximum angle (α) of a ramp onto which a vehicle can climb from a horizontal plane without interference (scraping) the ramp or incline.
INSTRUCTIONS: Choose units and enter the following:
ANGLE (α): The calculator returns the approach or departure angle in degrees. However, this can be automatically converted to other angle units (e.g. radians) via the pull-down menu.
α° = Approach angle: ß° = Departure angle
Break-over Angle (β )
Camber Angle (Φ)
Approach angle (α) is the maximum angle of a ramp onto which a vehicle can climb from a horizontal plane without interference. It is defined as the angle between the ground and the line drawn between the front tire and the lowest-hanging part of the vehicle at the front overhang. Departure angle (ß) is its counterpart at the rear of the vehicle – the maximum ramp angle from which the car can descend without damage. Approach and departure angles are also referred to as ramp angles.
Approach and departure angles are indicators of off-road ability of the vehicle: they indicate how steep obstacles, such as rocks or logs, the vehicle can negotiate according to its body shape alone.
To calculate your approach or departure angle, put your vehicle on a flat and level surface. Next, measure the height (h) and length (l) and enter the values into vCalc. To measure the height and length, take a straight rod or board, wedge it under the tire from directly in front of the tire for the approach angle or directly from behind the tire for the departure angle, and then rotate it up unit it touches the vehicle. The location where it touches is the impact point. The length (l) is the measure from the impact point to the ground where the rod touches the ground wedged under the tire. The height (h) is the vertical distance from the impact point to the ground. (See diagram)
Wikipedia - http://en.wikipedia.org/wiki/Approach_and_departure_angles