Brake drum is an important component in automotive, which is a link between axle and wheel. It performance is of utmost importance as it is related to the safety of the car as well to the passengers. Many design parameters are taken into consideration while designing the brake drum. The sensitivity of these parameters is studied for optimum design of brake drum. The critical parameters in terms of reliability, safety & durability could be the cross section, thickness of hub, interference & surface roughness between bearing and hub, wheel loading, heat generation on drum, manufacturing and assembly process. The brake drum design is derived by considering these parameters. Hence the sensitivity of these parameters is studied both virtually & physically, in detail. The optimum value of each parameter could be chosen complying each other's values. In this study it could be found that the proof stress for hub material can be crossed due to reasons of a) excess interference between wheel bearing and hub and uneven contact stress due to influence of form errors (cylindricity) & b) vehicle load transfer during cornering maneuvering condition. To have cost effective & optimum design performance of cast iron (CI) brake drum; it is compulsory and evident to study variation of all parameter under all operating & abuse conditions for the uncertain behavior of gray cast iron and manufacturing process variations.