This paper proposes a systematic method to optimize wheel torques in a compliant modular robot, which consists of 3 link-wheel modules connected by revolute joints. Conventionally, actuators are used at these joints for posture control while climbing. In this work, use of torsional springs at the joints is proposed for posture control. The compliance thus obtained is profitably used to manoeuvre on uneven terrains. It is also shown how the springs are designed to be stiff enough to restrict the link-wheel module from tipping over while climbing big step-like obstacles. The only actively controlled variables of the robot are wheel torques, which are optimized to minimize wheel slip. This helps in reducing odometric error and maximizing energy efficiency. The proposed optimization builds on the quasi-static analysis of the robot and forms one of the key novelties of this paper. The results show the advantages of modularity in climbing big steps without any slip. The proposed wheel-torque optimization lends utility in the design of an appropriate wheel velocity controller.