The material properties of cord‐rubber composites required for finite element analysis of tires are discussed. It is shown that the current experimental methods used in verification of the Laminated Plate Theory have not adequately included the coupling deformations existing in unsymmetrical laminated composites. The importance of these coupling deformations is demonstrated on a 0/90 laminated strip. A special grip system capable of decoupling loads and moments applied to a 0/90 laminated strip is introduced. A procedure for experimental determination of the stiffness constants of 0/90 laminate is given.