A strain gauge measures elongation and compression at a surface of a component. The strain gauge comprise a housing having a fixation configured to attach the strain gauge to the surface to be measured, a connector for contacting a measuring cable, at least two support surfaces at the housing for securely bearing on the surface to be measured. At least one of the support surfaces is provided with a transduction element and with a measuring element for measuring shearing forces. The measuring element is connected by an internally disposed cable to the connector and to a module that comprises that at least one support surface provided with the measuring element pre-assembled together with the transduction element.