Brake drum failure due to cracking is a significant concern in the design of automotive brake systems. A dynamometer simulation of typical highway driving conditions indicated that for a gray cast iron drum to be resistant to large crack formation under typical driving conditions it should have a high graphite content. Drums with a relatively thin wall may also be more resistant to large crack formation however additional testing is required. Graphite flake length and drum hardness were not found to have an effect large crack formation. Defining the characteristics of drums resistant to large crack formation and failure can lead to safer, more efficient drum designs.