Approach, departure and ramp-over angles explained
Off-roading, four-wheel driving, 4WDing – whatever you want to call it – can sometimes seem like a dark art, a dirty science, especially to those starting out in the wonderful world of “wheeling”.
It’s a passionate sub-culture full of mechanical terms, seemingly difficult-to-grasp skillsets, and it’s also a community peppered with words and phrases that may be tough to decipher, at least at first.
Case in point: often you’ll see in any of our reviews on SUVs, AWDs, 4WDs – or really any vehicles that are even remotely marketed as “off-roaders” – that we'll make reference to a vehicle’s approach, departure and ramp-over angle (sometimes referred to as break-over angle or ramp break-over angle), usually when we're writing about a vehicle's suitability for off-roading – in theoretical and, more importantly, practical terms.
I bet some of you are thinking: “What the bloody hell are those and why are they important?”
They're crucial because they're measures/values that give a direct indication of how well your vehicle is suited to be driven up, over and down obstacles or irregular terrain – and whether it can do those tasks without sustaining damage.
So, just what do these terms refer to, what are these angles, what’s a good measure for each when it comes to off-roading, and why are they so important to safe, sensible and comfortable off-roading? Read on.
What is your vehicle’s approach angle?
Imagine this: While off-roading, you’re faced with a steep hill. You stop at the base of the incline and prepare to drive up it, but the hill is so steep that the front of your vehicle touches it before your tyres even get a chance to – the angle of the hill is greater than your vehicle’s approach angle.
If you persist and try to drive up the hill, you may get stuck and/or do some damage to the front and undercarriage of your vehicle in the process.
Note: A vehicle with a short overhang at the front will have a greater approach angle than one with a longer overhang. Also, if your vehicle has a bullbar, winch etc that will affect your approach angle, by effectively reducing it.
What is your vehicle’s ramp-over angle?
Ramp-over angle refers to the angle between your tyres and the centre of your vehicle’s underbody; if your vehicle has too shallow a ramp-over angle for the terrain it is driven on, then it will scrape over or even get ‘hung up’ on minor obstacles.
Imagine this: you’ve driven up the steep hill I mentioned above. Your approach angle was enough to get you up the incline but as you proceed over the hill your vehicle’s undercarriage becomes well and truly grounded on the crest. If you try to drive off of it you risk significant damage to your vehicle’s underbody. The angle of the crest is greater than your vehicle’s ramp-over angle.
Note: A standard vehicle with a longer wheelbase is more inclined to have a shallower ramp-over angle than one with a short wheelbase.
What is your vehicle’s departure angle?
The departure angle is simply the same principles, as mentioned above, but applied to your vehicle’s rear bumper and rear tyres.
Imagine this: you’ve driven up a hill, you’ve crested it without grounding out at the top and you’re driving down the other side. As you drive slowly back onto flat ground, the rear of your vehicle just clears the downslope. Congratulations: your vehicle’s departure angle is greater than the angle of the decline.
A vehicle with a short overhang at the rear will have a greater departure angle than one with a longer overhang there.
Vehicles with short wheelbases, such as the Suzuki Jimmy, fare rather well in terms of all of these measures and it shows in their performance in low-speed off-roading.
Note: A tow bar will affect your vehicle's departure angle, by effectively reducing it.
How to improve your vehicle’s approach, departure and ramp-over angles
This involves modifying your vehicle from standard with bigger off-road-suited tyres and lifted suspension – doing this will instantly improve any vehicle’s off-road prowess. Keep in mind though that any vehicle must only be modified within legal limits and that throwing this gear on a low-riding AWD will not turn it into an all-conquering off-road weapon.
That doesn’t mean you’re not able to have great adventures in a standard 4WD, AWD or even a 2WD with far-from-ideal ground clearance measures and approach, departure and ramp-over angles.
You simply need to drive to suit the vehicle, the terrain and the conditions and, at all times, use your commonsense and err on the side of caution.
Don’t take an AWD with low ground clearance into ‘4WD only’ territory, and don’t take on any obstacle you have not properly scrutinised first.
A good general rule with regards to approach, ramp-over and departure angles is: smaller double-digit figures are fine for light-duty AWD off-roading – for example, a Mitsubishi Outlander AWD has rather modest approach (19.5 degrees), ramp-over (19) and departure angles (21). For moderate to difficult off-roading, figures more in the vicinity of the Jimny's approach (37 degrees), ramp-over (28) and departure (49) angles are much better.
If you know your vehicle’s capabilities, drive to suit them and drive sensibly, you’ll be better equipped to go off-roading and avoid delays, damage and any strife.