The main reason for the definition of leaf springs as safety parts is that even the smallest mistake in its functioning can cause severe accidents. It is imperative to ensure the endurance of leaf springs under high deformation and stress.In this reference study, we examine deviations resulting from production and design variations known as” noise factor” which can affect the fatigue life of a parabolic leaf spring. It will be a mistake to evaluate the design roughly with the stress levels on the layer. It has been described in this study with relevant examples that the leaf spring with 1550 N/mm2 tensile strength may be broken under much lower stress levels if it is exposed to dynamic loads.Criteria for the eye forms design and the fatigue behavior of eye forms, the effect on fatigue of leaf spring end form differences, the effect on fatigue of leaf springs with the same rate value designed in different cross-sections, u-bolt fixing force effects and similar topics have been verified with finite element analysis and endurance rig outputs, and the evaluation results are presented in this study. This study, carried out for different parameters on the same spring, can be used as a reference by leaf spring designers.