The causes of this type of accident vary but are usually the result of a combination of forces acting upon the tractor at the same time. One force affecting tractor stability is the pull which gravity exerts upon it. A tractor's center of gravity is the point at which all parts of the tractor exactly balance one another. The center of gravity on the average tractor is located about 2 feet in front of and 10 inches above the rear axle. When the center of gravity is maintained in this position the tractor cannot be upset.
Rear overturns occur when other forces move the center of gravity back over the rear axle.
Another force is rear-axle torque. When the clutch is engaged, a twisting force is applied to the tractor's rear axle to rotate it and move the tractor forward. But if the axle is restrained in some way, and sufficient power supplied, something has to give. The front end lifts off the ground and rotates the tractor backward around the axle. When the front end passes the point of no return, momentum takes over and completes the rearward flip.