The objective of this paper is to highlight the design, analysis, testing, and application engineering performed to develop a lightweight brake drum made of aluminum metal matrix composite (MMC). Current cast iron brake drums are “design-limited” in the sense that new designs do not significantly change performance and they offer minimal weights savings. This paper will begin with the design of the drum with respect to SAE requirements, and then show how the drum was optimized using finite element analysis (FEA). FEA was used to predict maximum drum temperatures and stress levels reached during various braking events. There were a number of design iterations that led to the current design that has been extensively tested on the dynamometer and on a vehicle. In addition to test performance, the casting and infiltration challenges led to significant design changes. Finally, this paper will present dynamometer and vehicle test data with direct comparisons to cast iron drums, especially related to the concerns with fade, torque and temperature. The engineering effort, coupled with the testing success, demonstrate that this lightweight brake drum product brings a significant weight reduction benefit while fulfilling market drivers - stopping distances, emission reductions, rising fuel prices, and growing weight of military vehicles. Prior attempts to make heavy truck drums involved making the drums of 100% MMC reinforcement, and were unsuccessful. The selective MMC reinforcement method is used here, and has demonstrated a new level of success.