The Stability Triangle

Forklift operators also need to understand the concept of the forklift stability triangle. A typical forklift, meaning a sit-down counterbalance lift truck, has a three-point suspension triangle with the weight supported by the two front tires and the center of the rear axles. Almost all counterbalanced powered industrial trucks have a three-point suspension system. This is true even if the vehicle has four wheels. When the points are connected with imaginary lines, this three-point support forms a triangle called the stability triangle, depicted here with dashed lines.

Consider the following:

• When the vehicle load center falls within the stability triangle, the vehicle is stable and will not tip over. For safe operation, the center of gravity of a loaded forklift must stay within this stability triangle.
• However, when the vehicle/load combination falls outside the stability triangle, the vehicle is unstable and may tip over. Beyond a certain point, tipping over is inevitable. Remember to add the weight of the forklift's attachment(s) in the calculation of maximum load.
• When a forklift is unloaded with its forks down, its center of gravity is right below where the operator sits.
• When the forklift is loaded, the center of gravity moves toward the fork. However, it can't extend beyond the stability triangle without risk of tipping longitudinally.

Other types of forklifts, such as a stand-up narrow aisle forklift, have different stability concerns. Employers are responsible for providing training specific to the types of forklifts employees will be operating.

To learn more about Forklift Safety visit our Forklift Safety Online Training web page.