Sealing rings for use with an outer curing envelope to retread a tire. Each ring includes an outwardly opening annular channel member having a base portion molded to conform to the contour of the tire bead, and an annular outer flange portion having an enlarged sealing rib for underlapping the outer curing envelope at the outer side of the tire casing near it maximum width. Two rings are required, one on each side of the tire casing, to form with the outer curing envelope a complete seal enclosure around the outside tire.