Finding the center of gravity height can be done in several ways, none of which are accomplished very easily and without some work. Presented here is the easiest method. The center of gravity height is calculated by weighing the car when level and then raising the car at least 10 inches at the rear and weighing the front again. Enter the data into the program below to calculate your center of gravity height.

Before you begin:

• Be sure that all fluids are full

• Replace each shock absorber with a solid link to eliminate suspension travel

• Make sure the tires are inflated to the maximum pressure as specified by the manufacturer to eliminate any sidewall flex

Note:  If these steps are not taken, the calculations will be inaccurate

 Center of Gravity Height Formula Definition of Variables CGH - Center of Gravity Height WB -  Wheelbase (inches) TW - Total weight  FW1 - Front weight LEVEL FW2 - Front weight RAISED FWc - FW2 - FW1 (change in weights) HT - Height raised (inches) Adj - Adjacent side (see below) Tan q - Tangent of angle (see below) CLF - Left Front tire circumference CRF - Right Front tire circumference C - (CLF + CRF) / 2  (average circumference) r - Axle Height Related Formulas

This program is used to calculate center of gravity height. Enter the data in the boxes below, then click the "Calculate" button.

Wheelbase (inches)

Total Weight (lbs)

Front Wheel Weight - Level (lbs )

Front Wheel Weight - Raised (lbs )

Raised Height (inches)

Left Front Tire Size (circumference in inches)

Right Front Tire Size (circumference in inches)

Center of Gravity Height from Axle Height

Center of Gravity Height from Ground

How does all this work?

 The center of gravity height is found using the rules of trigonometry and right triangles. Specifically, we are using the Law of Tangents, and the Pythagorean Theorem.  The following diagrams are greatly exaggerated for illustration purposes. Tan q = opposite / adjacent Pythagorean Theorem Figure 1 So, in our exercise, when we raise the car 10" we are creating a right triangle with the following properties: Hypotenuse = Wheelbase = c Opposite = Height = b Adjacent = a Therefore using the Pythagorean Theorem: Figure 2 Once we know the value of the adjacent side of our triangle we solve for the tangent of q using: Figure 3 Ok, now that we know the tangent of the angle we can calculate the center of gravity height based on our weight measurements using the following formula: WB is the wheelbase FWc is the change in front wheel weights TW is the total weight Tan q is the tangent calculated above This calculates the Center of Gravity Height from the axle height. To find the CGH from the ground, you must add your axle height to the above calculation. You can measure your axle height or calculate it using the average of your two front tire sizes and the formula for the circumference of a circle. C is the average circumference found by adding the LF and RF sizes and dividing by 2. p approximately equals 3.1416 r is your axle height For example: Your LF is 85.5" and your RF is 87". Your average circumference is (85.5 + 87) / 2 = 86.25". Your axle height is (86.25 / 2) / 3.1416 = 13.727".  Add this number to the CGH to find the center of gravity height in relation to the ground.