Who would have thought that the geometry we learned in high school would ever matter, especially when we are off-roading with our friends? Surprisingly it does matter - especially if you want to keep your shiny side up!
Approach Angle: Represents the steepest hill your vehicle can climb without brushing, or slamming, its front bumper against the slope.
Break-over Angle: An indication of the steepest crest a vehicle can traverse without high centering.
Departure Angle: Represents the steepest grade your vehicle can descend without brushing, or slamming, its rear bumper against the slope.
High Centered: When the crest is too big, the Break-over Angle is maximized, and the vehicle will rest on the skid plate, or lowest resting spot. Both sets of wheels will have NO traction on the ground.
Putting it into Context
The approach and departure angles are a function of ground clearance, as well as front and rear overhangs. If you have short overhangs and lots of ground clearance, you will have a very good approach and departure angles, allowing you to ascend and descend steep slopes.
Look at the front and rear of your vehicle to understand your lowest hanging items that would come into contact with an obstacle first - fog lights, bumper, exhaust pipe or trailer hitch. Keep these items at the front of your mind when you are considering an obstacle. Always approach an obstacle slowly so you don't slam into it, and potentially damage your vehicle. When the front components clear, and the front tires start to climb, you have successfully managed your approach angle!
The break-over angle is a function of ground clearance and wheelbase. A shorter wheelbase and good ground clearance will allow a vehicle to travel over sharp crests. The longer the wheelbase, the smaller the break-over angle you are able to tackle. Vehicles with a short wheelbase and high center have a definite advantage in these situations. When shopping for a new vehicle, consider the wheelbase - what you are used to and want to improve.
Another way to think of the break-over angle is to not be stuck as a teeter-totter. When your front wheels crest the hill, you need enough clearance to allow the wheels to continue driving, versus being "high-centered". If you can go straight over an obstacle while all 4 tires are still touching the ground, and you don't drag or get stuck on your skid plate, you have accomplished a break-over point!
Increase Your Angles
There are two ways to increase your approach, departure and break-over angles. Line up to the obstacle at an angle, or increase your ground clearance.
We have been talking about taking an obstacle at a 90-degree angle, or straight on. Most of the time in off-roading we don't approach anything straight; we tend to take the obstacle at an angle. Approaching at an angle allows one tire at a time to hit the obstacle and splits the approach angles.
You can increase your ground clearance with different aftermarket parts, including a suspension lift and/or taller tires. When looking at purchasing items such as bumpers, consider if this item will help increase or decrease your angles. Some vehicles have the opportunity to lengthen or shorten their wheelbase in the aftermarket world.
Measuring Your Angles
You don't need a protractor to measure your vehicle's angles. If you don't want to risk damaging your vehicle through trial and error, try this method: Take a long, straight object such as a yardstick, broomstick or board, and place one end where the front of your front tire touches the ground. Lift the other end up until it hits the lowest point of the front of your vehicle (usually this is the bumper). The angle of the object is your specific approach angle. Repeat the method in the rear for your departure angle.
You don't need to know exactly what the degree of approach is, but you do need to know what it looks and feels like on a trail. Practice makes perfect in this situation. As you are out on the trail, or in a play-ground area at your local off-road park, take some time to try "pulling up" onto obstacles. When you look at an obstacle and try to pull up on it in an effort to understand if your vehicle will clear it, you will start to train your eye on your vehicle's capabilities.
Break-over training is a little harder because you may actually get yourself high-centered - so, practice this with a winching friend in tow! DO try it. Look at the top of a cresting hill and understand how steep it is on both sides. Then SLOWLY and easily do the climb, and let the front wheels roll over to the other side. You will understand if your vehicle can clear it, rub its skid-plate, or high-center. If you approached slowly, you will be able to feel this before you find yourself in a bad situation. Simply put it into reverse and look for another hill that doesn't have as steep sides. You will start to understand what your vehicle is capable of - I bet it is more capable than you give it credit for!
Traction and Momentum also play into the equation of getting over or through the obstacle. We will talk about those soon!
Author: Charlene Bower P 1/12/2017
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