Brake linings used in automobile brake systems are complex composite formulated from asbestos fibers as reinforcement, organic resin as binder and different fillers and additives used to obtain the required characteristics, which satisfy highly stable braking performance. The objective of this work is to study the effect of changing the grain size of some constituents of the brake lining materials on its characteristics. To achieve this goal sieving analysis of the chosen constituents ( Brass, Graphite, and Magnesium oxide ) was made and samples of different grain sizes were prepared and tested using the Friction Assessment and Screening Test machine (FAST) to evaluate the friction and WOar Characteristics. Tensile, compression and hardness tests were also conducted to evaluate the mechanical properties. The results showed that increasing brass chip size gives better friction and mechanical behavior while reducing brass chip size gives suitable wear resistance. Finer graphite grain size gives better friction and wear resistance while coarse graphite grain size gives reasonable mechanical behavior. Fine magnesium oxide grain size gives good friction, wear and mechanical behavior.