An apparatus for retreading a heavy duty tire with a polyurethane tread where a tire carcass that is suitable for retreading receives a tube fitted therein and is installed on its side in a mold cavity, between top and bottom rings, that each include spaced segments extending from opposing top and bottom ring surface that inter-digitate to form the equal spaced tread voids in a finished recapped tire, with bottom ring inner edge including a continuous sealing lug, and the top ring is open to pass a flow of polyurethane materials from a lower edge of a cone shaped spreader that is positioned onto the tire carcass top side wall and directs a flow of polyurethane materials from the cone surface into the mold, filling the mold cavity from bottom to top to form a recapped tire tread.