Although gerotor pumps are used in a wide range of industrial applications, higher work pressure causes shock or collision among pump components, which leads to large stress fluctuations and shortened pump life expectancy. This paper therefore proposes a novel variable clearance design that diminishes such component collisions. After a geometric mathematical model is constructed of variable clearance rotors, a fluid analysis model is developed based on a relief groove design. Applying the model to two fixed clearance and three variable clearance designs demonstrates the effects of various fixed clearance sizes on gerotor pump performance and identifies the differences between fixed and variable clearance designs. The results support the feasibility of the proposed design: the appropriate variable clearance designs maintain robust flow characteristics and effectively reduce shock and collision among pump components, thereby reducing stress level, increasing stability, and extending the life expectancy of the gerotor pumps.