Most special vehicles on public roads and off-road are equipped with various suspension systems. The suspensions used in trucks are designed to absorb the energy that results from overcoming uneven ground. These suspensions are divided into dependent and independent ones. Knowledge of the loads that occur while driving a vehicle, mainly off-road, is critical from the point of view of the adhesion and fatigue life of the suspension system. In the case of four-axle cars with 2 + 2 axles, in which the first two axles are equipped with a dependent suspension based on leaf springs, only one axle may carry the load. This paper attempts to analyze the results of experimental tests carried out on a vehicle in the conditions of roads with an unstable surface such as dirt roads, gravel roads, and roadless tracks. An analysis of fatigue life estimation is presented using equivalent stress values. It was also determined how the use of front axles load equalizing elements in the tested car influences their fatigue life.
Keywords: experimental results of front suspension; four-axle truck; parabolic leaf spring.