Cast iron/aluminum composite brake disks are increasingly being employed, as they offer improved fuel efficiency and a lower unsprung mass. The achievable mass reduction and the product costs are determined by the joining concept.This paper presents two novel lightweight composite brake disks, which are produced using two different joining methods. The connection of the first lightweight brake disk under investigation in this study is implemented by friction welding. The second brake disk uses the forming processes spinning and flow forming. The requirements regarding the design of the concepts are presented in the course of this paper. Both lightweight concepts have been validated in standardized tests on a test bench. The results of the experimental investigation are discussed regarding to the key aspects of mass reduction, thermal and mechanical behavior and production.