A support bracket for supporting insulating rods inside an insulator tube of a hollow core insulator. The support bracket includes a cylindrical ring with an outer surface for abutting against the inner surface of an insulator tube, an inner surface for supporting an insulating rod and two opposing end sides, denominated by first and second end sides. The support bracket includes an expansion assembly configured to be actuated so as to expand the cylindrical ring in at least one radial direction when the support bracket has been inserted in an insulator tube of a live tank circuit breaker.