The study of fatigue crack growth resistance for tire belt compounds is motivated by the high deformation cycles inherent in the belt edge region of radial tires. To improve the understanding of fatigue in this region, a test has been developed to simulate crack growth in shear (mode III). A rubber disk with a circumferential pre‐crack is tested in cyclic torsion to simulate belt edge interlaminar shear cycles. Theoretical, numerical [finite element analysis (FEA)] and experimental methods have been employed to investigate and quantify the response. A recent improvement to the analysis considers nonlinear elastic material behavior which is characteristic of carbon black‐filled tire compounds. The best agreement between torsional test results and results from typical thin sheet geometries was found for lightly reinforced compounds; crack branching often complicates results for more highly reinforced compounds. Fracture surfaces are examined for evidence of non‐planar crack growth to help interpret the results.