Whether you’re planning on taking your truck off-road or just enjoying your car as a daily driver, knowing your vehicle’s center of gravity can be an important piece of information. But what is the center of gravity, and how can you figure out where it is in your vehicle?
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What Is the Center of Gravity?
The center of gravity of any vehicle is the point that sums up the vehicle’s mass in one central point. To put it simply, it is the average location of the weight of an object.
In the human body, the center of gravity is somewhere around the second sacral vertebra. In your car, it is usually somewhere just ahead of the center point of your car.
Why Does This Matter When Driving?
Your vehicle’s center of gravity comes into play most often when the car is making a turn. When you drive around a turn, particularly at higher speeds, the momentum of your vehicle transfers the load which causes the body of the car to lean in that direction. That’s why in a car with a higher center of gravity, taking a turn at a high rate of speed can cause the car to flip over — the center of gravity isn’t able to compensate for the body lean, and the car falls over.
You can control the lean in your vehicle by either lowering the center of gravity or widening the wheel base of the car. Things like springs, anti-roll bars and roll center heights are also useful tools to prevent rollover and reduce lean.
Track cars, ones like the Mustang or the Focus RS that are designed to take turn at high speeds, have a lower center of gravity that helps them hug the ground when while they’re turning. The low center helps to compensate for the inevitable lean they experience while turning.
Big vehicles designed for off-roading like the F-150 or the Jeep Wrangler, on the other hand, have a wide wheel base that helps to compensate for the body lean when they’re turning. It also increases stability when you’re driving on rough terrain.
How Do You Calculate Center of Gravity?
Finding a vehicle’s center of gravity will take a bit of math and a bit of measurement — think of it as a throwback to your high school geometry class.
First, you need to find two angles — the roll-over angle and the sideways roll-over angle.
The roll-over angle is the angle you find when you draw a line between the supporting wheel and the center of gravity. The angle will appear between that line and the ground.
The sideways roll-over angle is the angle between the ground and a line drawn between the outer limits of the wheel track and the center of gravity.
Here are a couple of center of gravity formulas you will need to write down. First, you need to find the front-to-rear bias to find the distance between the center of gravity and the centerline of the front axle — divide the rear wheel vehicle weight by the overall vehicle weight and multiply that result by the wheelbase.
(Rear Wheel Vehicle Weight / Overall Vehicle Weight) X Wheelbase
Next, you need to find the side-to-side bias to figure out how far away the center of gravity is from the centerline of the vehicle.
(Weight of Passenger Side / Overall Vehicle Weight) X Track Width
Finally, you need to figure out the top-to-bottom bias to figure out how high your center of gravity is. Determine the level vehicle wheelbase, the raised vehicle wheelbase, and the added vehicle weight on the front wheels and multiply them all together. Then multiply the distance the vehicle was raised by the overall weight of the vehicle. Then divided the first number you found by the second to get the top-to-bottom bias (height center of gravity).
(Level Wheelbase X Raised Wheelbase X Overall Weight) / (Distance Raised X Overall Weight)
By putting the results of those three formulas together, you will be able to determine the location of your car’s center of gravity. Once you have that information, it’s a lot easier to modify your car and turn it into something you love to drive.
Center of Gravity Example for a Ford Mustang
Date points for a fully loaded 2017 Mustang GT Premium Fastback with a full tank of gas and no driver:
- Overall Weight: 3,705 lbs.
- Weight of Passenger Side: 1,849 lbs.
- Rear Wheel Vehicle Weight: 1,741.4 lbs.
- Track Width: 63.6 inches
- Wheelbase: 107.1 inches
- Raised Wheelbase: 107.57 inches - based on raising the rear of vehicle 10 inches (We can calculate this via the Pythagorean theorem) Since we raised 10 inches, the raised wheel base is 107.57 - this is the sqrt (107.1^2+10^2)]
- Added Weight on Front Wheels: 34 lbs.
(1741.4/3705) x 107.1 = 50.33
This means the front-to-rear center of gravity is 50.33 inches behind the front axle centerline.
(1849/3705) x 63.6 = 31.74
This means the side-to-side center of gravity is 31.74 inches from the left side track point of the car.
(107.1 x 107.57 x 34) / (10 x 3705) = 10.57
This means the top-to-bottom center of gravity is 10.57 inches above the axle height.