of expanded portion 80 of diaphragm 78 retaining member 120 will be better understood with reference to fig5 of the drawings which shows retaining member 120 detached from its position on brake actuator 20 in this embodiment retaining member 120 comprises a ring of metal such as steel or the like and includes tensioning or compression portion 122 which is formed by joining ends 124 and 126 of body 128 of retaining member 120 any number of means may be used to join ends 124 and 126 as long as a strong connection is formed as by spot welding or the like with reference now to fig4 retaining member 120 is placed in position such that it receives abutting rim 118 and flange 84 of brake actuator and groove or channel 130 channel 130 being shown best in fig6 which is a cross section of ring body 128 also as shown in fig6 chamfered or beveled surfaces 132 are provided to facilitate the installation of retaining member 120 onto abutted rim 118 and flange 84 that is chamfered surfaces 132 act as guides or the like so that retaining member 120 can be easily installed onto rim 118 and flange 84 it is to be understood that the inner diameter of the ring or circle formed by body 128 is 34 over sized 34 to facilitate the placement of retaining member 120 over the flange 84 and rim 118 once retaining member 120 is in its initial position referring now to fig7 tools 134 are used to crimp tensioning portion 122 to tighten body 128 around rim 118 and flange 84 so that head 116 is tightly attached to flange case 28 that is sections 136 of tensioning portion 122 are deformed beyond their elastic limit using.