Departure Angle

Departure angle is a measure of how steep a slope a vehicle can drive off, or reverse down, without its rear bumper or underbody fouling the ground. It is defined as the angle formed between the road surface and a line drawn from the rearmost point of the tyre contact patch up to the lowest-hanging part of the vehicle behind the rear axle. A larger angle means the back end can clear a sharper crest or a steeper exit from a dip, which is why it is one of the standard trio of off-road geometry figures.

The angle is set almost entirely by two physical dimensions: the length of the rear overhang, meaning how far the body extends behind the rear wheels, and the ground clearance at that point. A short overhang tucks the bumper close to the wheels so the ground can fall away steeply before anything touches, while generous clearance lifts the obstruction higher. Anything hanging low at the rear, a towbar, a spare wheel slung beneath the floor, an exhaust tailpipe or a protruding bumper, reduces the effective angle regardless of the bodywork above it.

The practical importance becomes obvious the moment a vehicle crests a sharp ridge or climbs out of a gully. As the front wheels descend the far side, the rear of the car pivots downward toward the slope behind, and if the departure angle is too shallow the rear bumper or tow hitch digs into the bank, halting progress, lifting the driven wheels or causing expensive damage. The same situation arises at the top of a steep ramp or a kerbed driveway, where a low-slung sports car can ground its rear valance on terrain a 4x4 would ignore.

This is why purpose-built off-roaders are styled with stubby rear overhangs and high-mounted bumpers, frequently quoting departure angles of thirty degrees or more, whereas a long, low saloon or estate may manage only ten to fifteen. Designers of vehicles such as the Land Rover Defender or Jeep Wrangler deliberately keep the tail short and the load floor high to maximise the figure, sometimes integrating the spare wheel and recovery points to avoid compromising it.

Departure angle never works in isolation. It pairs with the approach angle at the front and the breakover angle in the middle, and a vehicle is only as capable as its weakest of the three. Fitting larger off-road tyres or a suspension lift improves it, while lowering a car, adding a heavy roof tent that compresses the springs, or hitching a trailer can worsen it. Read alongside approach angle, breakover angle and ground clearance, it gives a rounded picture of where a vehicle can and cannot go.