A process and method for retreading a heavy duty tire with a polyurethane tread where, after a tire carcass is inspected, cleaned and the worn tire tread is removed, the tire carcass receives a tube fitted therein and is installed in a mold cavity, between top and bottom mold rings. The mold rings each include spaced segments that inter-digitate and will form equal spaced tread voids in a finished recapped tire. The bottom mold ring inner edge top includes a continuous sealing lug, and the top ring is open to pass a flow of polyurethane materials, that is received off of a lower edge of a cone shaped spreader positioned onto the tire carcass top side wall and slides, as a sheet, into the mold, filling the mold cavity from bottom to top, forcing air from the mold ahead of the fill and forming the recapped tire tread.