An enhanced version of the Rubber Cord Adhesion Inflation Test (RCAIT) has been designed to experimentally assess the internal pressure and cable tension applied to the specimen needed to propagate a crack along the matrix/reinforcement interface. To calculate the critical strain energy release rate, we develop a semi-analytical model describing the deformation of a hyperelastic tube under loading conditions that reflect the ones applied experimentally. A more comprehensive numerical model of the test is also proposed to investigate the influence of loading conditions on rubber deformation near the crack tip. Comparison of different experimental data sets with the theoretical/numerical data demonstrates that the new experimental setup allows for a reliable determination of the rubber/cord interface failure envelope under combined loading conditions.