An experimental study was carried out to understand the role of inhibitor flexibility on the flow–acoustic coupling characteristics of simulated solid rocket motors. Sub-scale experiments are conducted using an axial cold flow model with inhibitors made of elastomers simulating the obstacle vortex shedding mechanism at the segment interfaces. The cold flow setup replicates the geometry inside the solid rocket motor at the instance of maximum pressure oscillations noticed during full-scale static tests, with the similarity of the Mach number inside motor’s port being maintained. In the region of flow–acoustic coupling, the role of inhibitor flexibility is investigated by varying the thickness and material for a specified set of diameter ratios. Results show dependence of inhibitor flexibility on the time of occurrence of peak oscillations. Also, the experiments done with inhibitors having natural vibration frequencies in a close match with the first acoustic mode show heightened oscillations demonstrating the effect of fluid–structure interaction. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.