A gyratory crusher comprising: a bowl shaped as a cone with its wider opening approaching the top of the crusher; a head assembly shaped as a cone, centrally located within the bowl and having its larger diameter at the lower end of the bowl, so that the bowl and head assembly form a crushing volume which is larger at the top and smaller at the lower end, with the head assembly including a central mainshaft which is located on an inclined axis within the bowl; a spider located at the top of the crusher functioning as the upper support member of the crusher and including bushings or bearings within which an upper portion of the mainshaft is captured; a cylindrical eccentric assembly including an eccentric central volume in which the mainshaft is held so that, as the eccentric assembly rotates, the mainshaft gyrates, with the eccentric assembly rotating about a center hole within a central hub of the crusher, said eccentric assembly being removable from the crusher; a ring gear attached to and rotating the eccentric assembly with the ring gear driven by a drive gear and a drive shaft; a hydraulic support assembly comprising a piston assembly installed within a cylindrical support, said hydraulic support assembly installed below and supporting the head assembly with the cylindrical support supported by a support frame ledge protruding inward from the structure of the crusher, and with the cylindrical support being sized to be able to clearly pass through the center hole when the eccentric assembly is removed, with the largest horizontal dimension of the cylindrical support being less than and clearing the smallest horizontal dimension within the center hole which is located above the cylindrical support, characterised in that the piston assembly contains all the designed wear parts within the hydraulic support assembly, said designed wear parts comprises an upper piston bushing, a lower piston bushing, a piston wear ring and a piston seal, and wherein, on the piston assembly, the upper piston bushing has larger diameter than the larger diameter of the lower piston bushing or the piston seal to facilitate the easy installation of the piston assembly from above. a bowl shaped as a cone with its wider opening approaching the top of the crusher; a head assembly shaped as a cone, centrally located within the bowl and having its larger diameter at the lower end of the bowl, so that the bowl and head assembly form a crushing volume which is larger at the top and smaller at the lower end, with the head assembly including a central mainshaft which is located on an inclined axis within the bowl; a spider located at the top of the crusher functioning as the upper support member of the crusher and including bushings or bearings within which an upper portion of the mainshaft is captured; a cylindrical eccentric assembly including an eccentric central volume in which the mainshaft is held so that, as the eccentric assembly rotates, the mainshaft gyrates, with the eccentric assembly rotating about a center hole within a central hub of the crusher, said eccentric assembly being removable from the crusher; a ring gear attached to and rotating the eccentric assembly with the ring gear driven by a drive gear and a drive shaft; a hydraulic support assembly comprising a piston assembly installed within a cylindrical support, said hydraulic support assembly installed below and supporting the head assembly with the cylindrical support supported by a support frame ledge protruding inward from the structure of the crusher, and with the cylindrical support being sized to be able to clearly pass through the center hole when the eccentric assembly is removed, with the largest horizontal dimension of the cylindrical support being less than and clearing the smallest horizontal dimension within the center hole which is located above the cylindrical support, characterised in that the piston assembly contains all the designed wear parts within the hydraulic support assembly, said designed wear parts comprises an upper piston bushing, a lower piston bushing, a piston wear ring and a piston seal, and wherein, on the piston assembly, the upper piston bushing has larger diameter than the larger diameter of the lower piston bushing or the piston seal to facilitate the easy installation of the piston assembly from above.