The purpose of research is to analyze the characteristics of damage and evaluate the cause of the damage of Reclaimer’s wheels at Mae Moh Mine. This research selects the types of damage that has the highest frequency to study the behavior of the damage, using the theory contact stress of Hertz (Hertzian theory). This research tests the mechanical properties of the wheels such as the chemical compositions, tensile test, micro hardness testing, the structure of wheel’s material testing, and  the traces of cracking testing with the scanning electron microscope (SEM). Afterwards we build wheel and track’s model to analyze by finite elements method. The research models working using conditions that conform to the cause evaluation of the damage occurring to the Reclaimer’s wheels to find maximum stress occurs on Reclaimer’s wheels. Then the research compares the results of damage from actual working data to the result of model of finite element method. The finding occurs the cracking from high stress below surface area by the Hertzian theory and fatigue and cracking to surface eventually.

Key words: Reclaimer, contact stress, Hertzian theory, cracking