This work presents the application of a first-order perturbation method to evaluate the eigensensitivity of brake carriers when local geometric alterations arise. This method can be applied both to establish dynamic acceptance conditions of manufacturing-related errors (concept of ‘eigenacceptance’) and to assess the variation of eigenfrequencies and eigenmodes when design variations are done (concept of ‘eigendesign’). As an application of the first concept, the adequacy of the proposed method has been tested in the eigensensitivity of the rest of ingate caused by the manufacturing process; and with regard to the eigendesign concept, an easy-to-use methodology for the redesign of brake carriers has been developed and correlated.