112 114 is filled with an appropriate liquid hydraulic fluid care should be taken to eliminate any air bubbles or other compressible fluids from within the tube the tube 110 is completely sealed and no fluid should normally be added thereto and none should be able to be removed therefrom through prolonged use the clutch plates and particularly clutch plate 120 may wear eventually during braking motion of piston 102 104 the worn clutch plate 120 may shift enough to cause piston 102 104 to bottom in opening 106 the tube 110 therefore has a normally closed conventional bleeding and refill valve 119 connected to it through which additional fluid may be added as needed and through which trapped air might be bled without hydraulic fluid leaking out seated atop and outside the upper side of the flexible tube 110 there is an annular disc like clutch plate 120 the clutch plate 120 is comprised of metal so that it may rubbingly engage the clutch plate 37 without appreciable damage to either of them over a considerable period of time the underside of the clutch plate 120 seats directly on the tube 110 and thereby is exposed to the hydraulic pressure within the tube 110 the top side of the clutch plate 120 rubbingly engages the above described clutch plate 37 the disc like clutch plate includes a short radial keying projection 121 at one side thereof of a width and size to snugly fit between the side walls of opening extension 108 for preventing rotation of the plate 120 with respect to tube 110 or bracket 42 especially when plate 120 rubbingly engages clutch plate.