As you learn to navigate the challenges of off-road driving, you will find that knowing your vehicle and its capabilities and how to read the terrain is crucial to your off-roading experience. Factors such as approach angle, breakover angle, and departure angle are essential characteristics of your vehicle that you need to know or know how to calculate.
Approach angle is the steepest angle a hill can have that your car’s front end will clear. Departure angle is the steepest angle a hill can have that your car’s rear will clear. Breakover angle is the angle between the middle low-point of the car and the tires, determining the apex angle you can crest.
Approach, breakover, and departure angles are relevant for climbing up or down steep inclines while off-roading, including climbing over large rocks or boulders.
Approach and departure angles are also known as “ramp” angles. We will explain each angle, how you can calculate the angles for your car, and how each will be different depending on your vehicle characteristics.
It’s unlikely that you would actually take measurements of terrain on the trail, but knowing your vehicle’s angles will give you a better intuitive sense of what obstacles you can and can’t tackle.
- What is Approach Angle for Off-Roading?
- What Is Breakover Angle For Off-Roading?
- What Is Departure Angle For Off-Roading?
- Ways To Improve A Vehicles Approach, Breakover, And Departure Angle
What is Approach Angle for Off-Roading?
I bet you never thought off-roading would lead to trigonometry. But here you are.
Understanding the approach angle of your off-road vehicle will give you better judgment of how well your vehicle will handle obstacles such as traversing large boulders, logs, or steep inclines.
The vehicle’s approach angle is defined as the angle between ground level and a line drawn from the lowest part of the front of the vehicle, usually the front bumper, to where the front tire touches the ground.
The approach angle of your vehicle will determine how steep of an obstacle you can climb or descend, without your bumper or other portions of the frame touching the obstacle or the ground.
This means you have enough clearance that the front tires touch the incline enough to begin climbing or touch the level ground as you come off an incline, without the bumper getting in the way.
Compare the short-nosed vehicle with large tires above to the vehicle below, which has a longer nose and smaller tires. The upper vehicle can roll up onto the obstacle thanks to its steep approach angle. The bumper on the car below, which has a shallow approach angle, will hit the rock before the tires can connect, making it difficult if not impossible to climb this rock without causing damage.
Approach angles will differ for each vehicle because several factors around the car’s design will affect the approach angle.
- Vehicle nose length. This is the distance the nose of the car extends beyond the front wheels. The longer the nose of the car, the shallower the approach angle would be for that vehicle. Conversely, a vehicle with a shorter nose will have a better approach angle and will be able to tackle steeper inclines.
- Tire size. Larger tires that lift the vehicle further from the ground will increase the approach angle, allowing you to tackle steeper inclines. Smaller or lower-profile tires will reduce the vehicle approach angle and limit the slope angle it can negotiate.
- Suspension. A jacked-up suspension that raises the vehicle’s body higher above the ground will improve the vehicle’s approach angle, allowing steeper slopes to be traversed.
- Bull-bars. Bullbars or nudge bars can reduce the vehicle’s approach angle if its supporting brackets extend under the front of the car to bolt onto the front chassis. This will be the new lowest point of the front of the vehicle and can also extend the length of the vehicle’s nose, reducing the approach angle.
- Front-mounted winch. A winch is a great vehicle recovery tool, but its location is essential. A winch installed on the front of the vehicle that hangs below the front bumper is not a good idea, as this will drastically reduce the approach angle of the car. Instead, install the winch above the front bumper.
You can use an online approach angle calculator to calculate the approach angle of your vehicle. You will need the distance measurement from the lowest point under the front of the vehicle to level ground. Next, you will need the measurement from where the leading edge of the front wheel touches the ground to the lowest point under the vehicle’s front, where you took the first measurement.
What Is Breakover Angle For Off-Roading?
The breakover angle of your off-road vehicle (also known as the ramp over angle) is vital to know to prevent getting your car stuck on a pivot point with one or two sets of your wheels off the ground.
Essentially, the breakover angle will determine how steep a peak the vehicle can traverse without the peak damaging the underside of your car.
The definition of the breakover angle is the maximum supplementary angle that the car can travers such that when one set of wheels are on one side of the apex and the trailing wheels on the other side of the apex, the apex of the peak does not touch the underside of the vehicle.
A vehicle’s breakover angle will influence the height of a peak it can summit, considering the steepness of the angle on either side of the peak.
How To Calculate Breakover Angle
You can use a formula to calculate the breakover angle for your off-road vehicle so you can have exact numbers to judge your vehicle’s ability.
You will need to collect data on your vehicle that you can use in the calculation, namely, the wheelbase measurement and the ground clearance.
The wheelbase is the distance from where the front wheel touches the ground to where the rear wheel touches the ground. It can also be described as the distance between the front and rear axel.
Your vehicle’s ground clearance is the distance from the ground to the lowest part of the bottom of the vehicle.
Once you have this data, you can use it in the formula to calculate the breakover angle, which is as follows.
Breakover angle = 2 x arctan(2 x ground-clearance / wheelbase)
If math is not your strongpoint, you can use an online breakover angle calculator to do the heavy lifting for you. You will still need the data you collected on the ground clearance and wheelbase and input these figures into the calculator. The calculator will then process the formula and show the breakover angle as a result.
Here are approach, breakover and departure angles for a few popular off-roading and overlanding vehicles:
Is Ground-Clearance The Same As The Breakover Angle?
Ground clearance and breakover angle are not the same things. The ground-clearance is the distance from the ground to the lowest point on the vehicle’s underside and doe not take angles or peaks into account.
Ground-clearance only factors in flat ground and will affect the depth to which you can drive through deep ruts or deep mud without scraping the vehicle’s underside.
Breakover angle takes the slopes on either side of the peak into account to make sure the underside of your vehicle will clear the apex of the peak.
What Vehicle Characteristics Affect Breakover Angle?
As with approach and departure angles, there are vehicle characteristics that will affect the breakover angle.
- Ground clearance. The ground clearance will affect the breakover angle of your vehicle. The greater the ground clearance, the greater the breakover angle of your vehicle.
- Wheelbase. The distance between the wheels will play a role in determining the breakover angle. The longer the wheelbase, the lower the breakover angle, and the shorter the wheelbase, the higher the breakover angle.
- Suspension. The suspension will affect the ground clearance, which affects the breakover angle.
- Tire size. Tire size will affect the ground clearance, which will affect the breakover angle.
- Low hanging components. Any components installed under the vehicle’s body that extend below the bottom of the chassis will lower the vehicle’s ground clearance, affecting the breakover angle. This can be exhaust mufflers and piping, driveshafts, and similar components.
A vehicle with a larger approach angle will typically be able to climb steeper banks or obstacles without hitting the front of the car on the obstacle.
For instance, a vehicle with a short nose and large tires, like the one below, will be able to get the front tires up on this rock without hitting the bumper.
What Is Departure Angle For Off-Roading?
Many people make the error of only taking into account the approach angle of their vehicle and forget about the departure angle.
The departure angle of your off-road vehicle is the counterpart to the approach angle. The departure angle is defined as the angle between ground level and a line drawn from the rear of the back tire to the lowest point on the car’s rear.
The departure angle of your vehicle will determine how steep of an angle your car will be able to climb so that your rear bumper doesn’t hit the ground as your back tires climb onto a slope. Or, if you are descending, it defines how steep of an obstacle you can drive down without your bumper hitting the obstacle as your tires come onto level ground.
As with approach angles, there are characteristics of the vehicle that will affect the departure angle capability of the car.
- Length of the rear end. The further the car’s rear end extends past the rear wheels, the lower the departure angle will be. A vehicle with a shorter back end will have a better departure angle for exiting steep slopes or boulders, logs, and other obstacles.
- Tire size on the rear wheels. Large tires on the vehicle will increase the departure angle. Low-profile tires or small tires will reduce the effective departure angle for the vehicle.
- Suspension. As with suspension affecting approach angle, it will also affect departure angle for the vehicle. A suspension that lifts the chassis higher off the ground will improve the departure angle.
- Tow hitch. Many tow hitch designs are configured to be below the rear bumper of the car. A tow hitch that has this configuration will lower the departure angle of the vehicle.
You can make use of an online departure angle calculator to work out the departure angle of your off-road vehicle. Write down the measurement from the lowest point on the rear of your car vertically to the ground to get a height value. The take the measurement from where the rear tire meets the ground to the lowest point at the rear of your car where you took the previous measurement.
Input these measurements into this online departure angle calculator to get an instant departure angle for your vehicle.
Ways To Improve A Vehicles Approach, Breakover, And Departure Angle
Negotiating steep hills and obstacles are all part of learning off-road driving techniques and improving your skill on this type of terrain. Knowing your vehicle’s capability in these circumstances is a great start, but is there any way to improve your vehicle for these obstacles or choose a vehicle that is well suited to this type of terrain?
Suppose you are not in a position to have a dedicated off-road vehicle. In that case, you may consider modifying your existing 4×4 vehicle to improve its off-roading capability, especially in the approach, departure, and breakover angle departments.
What modifications can you make to an existing vehicle to improve the climbing angles?
- Lift the suspension. You can modify the suspension on the vehicle that will raise the chassis higher above the ground. This will improve the approach, breakover, and departure angles of the vehicle. This is a job best done professionally as it can be a large, complex job. Changing the suspension can also be a relatively costly modification.
- Fit larger tires to the vehicle. Fitting larger wheels and tires to the vehicle will lift the vehicle’s height, which will benefit all three angle aspects for hill climbing. This is a cheaper option when compared to modifying the suspension or installing a new suspension.
- Reduce the extension of the front and rear of the car. These two aspects will improve only the approach and departure aspects of the vehicle. Manny off-roaders strip the front and back of their vehicles from all cosmetic bodywork that unnecessarily extends the front and rear length. This gives the car a naked, industrial look on both ends, and you would need to be happy with your vehicle looking this way. It does add a new level of ruggedness to the look of the vehicle, which most off-roaders are okay with. Stripping the unnecessary cosmetic bodywork can reduce the front and back length, thereby improving approach and departure angles.
- Armor plate the underside of your vehicle. Many off-roaders fit metal plates under their vehicle to prevent damage to the undercarriage when they get their breakover angles wrong. It may be worth considering this modification as a beginner off-roader.
If you are looking for the right off-road vehicle to get started enjoying Overlanding or wilderness trails, then picking the right vehicle from the beginning will be a big help.
- The car front end. Choose a vehicle where the leading edge of the front wheel is as close to the car’s front end as possible. This will give an excellent approach angle to the vehicle. Examples f vehicles with this feature are the Jeep Wrangler and the old shape Landrover Defender, both the 50 and the 110 series.
- The rear end of the car. A flat or short back end on an off-road vehicle will provide a good departure angle. Look for a vehicle where the trailing edge of the rear wheel is close to the vehicle’s back end. Once again, the Land Rover Defender 50 and 110 series old shape and the Jeep Wrangle are good examples of this.
- Vehicle wheelbase. A short wheelbase vehicle will have a better breakover angle than a long wheelbase vehicle. In this case, a short-wheelbase vehicle like a two-door Jeep Wrangler would have an advantage over a Ford F150, Toyota Tacoma, or any similar long-wheelbase truck.
Here are some the off-road relevant angles for a few popular off-roading and overlanding vehicles (in degrees):
|Jeep Wrangler JL 2-Door Sport
|Jeep Wrangler JL 4-Door Sport
|Toyota Takoma TRD Pro
|Toyota Four Runner TRD Pro
All this talk about angles and measurements is probably not something you thought you would be investigating when you developed an interest in off-road driving! However, they are necessary aspects of your vehicle to know so you are aware of the limitations of your vehicle.
Online calculators make it easy to figure out these important metrics for your car. Many off-road trails will warn you not to try a trail if your vehicle has a particular approach, departure, or breakover angle. If you don’t know these measurements for your car, you may tackle a trail that your car will not handle.
The alternative method is a trial and error approach, which could end up being, in the very least embarrassing, getting your vehicle stuck, or at the worst, cost you a lot of money in repairs!