Method of calendering the continuous ply of reinforcing threads, during which: said ply of reinforcing threads is positioned between a continuous upper sheet of rubber and a continuous lower sheet of rubber, said sheets of rubber having a width greater than the width of the ply of reinforcing threads, so that the two lateral parts of said sheets of rubber which are not vertically aligned with the ply of reinforcing threads form selvedges. The assembly formed in the preceding step is introduced into the nip of a calendering comprising at least two rolls, so as to cause the rubber to penetrate the spaces between the reinforcing threads. Prior to the ply of reinforcing threads and the sheets of rubber being introduced into the nip of the calender, the two selvedges of one of the sheets of rubber are turned up on themselves.