As polymer products are being used in ever more demanding applications eg. automotive and aerospace, the demand for high-performance polymers is rising. For a hard-soft material combination in an over-molding situation, TPE’s or TPV’s are often used. For high demanding applications, these materials can be replaced by thermoset rubbers eg. EPDM, NBR, … However, until recently, only little was known about the quality of adhesion between these two components in an over-molded product, being an important quality parameter for two-component injection molding. In previous research performed by the researchers, a mold for test plates has been developed for the thermoset rubber, thermoplastic material combination and knowledge of the adhesion in this process has been acquired. By using this knowledge, various samples could be produced and tested for their interfacial strength. Combing these test results with numerical simulations led to a method to simulate and predict the strength of the interface for the given material combination. Furthermore, the simulated product properties acquired by Autodesk Moldflow can be mapped on a structural mesh, to perform numerical simulations on the failure behavior of the product and interface. This procedure has been used to optimize the interfacial strength for a new product being an HDPE ring over-molded with a thick rubber layer of EPDM, performing as a wheel. Structural simulations have been performed on the as made product by peeling the rubber from the HDPE core. The discussed samples have been produced and peel tests on this samples show good correlation with the simulation results.