Tyre for a heavy duty vehicle, intended to be mounted on a drop-centre rim of the " 15° drop-centre type", with a radial carcass reinforcement made up of at least one layer of reinforcing elements, said tyre comprising a crown reinforcement comprising two working crown layers of reinforcing elements (41, 42) that are crossed from one layer to the next and make angles (α1, α2) of greater than 8° with the circumferential direction, said angles α1 and α2 being oriented on either side of the circumferential direction, and at least one layer of circumferential reinforcing elements, the crown reinforcement being capped radially by a tread, said tread being connected to two beads by two sidewalls, - said two working crown layers (41, 42) and said at least one layer of circumferential reinforcing elements being the only ones present to form the crown reinforcement over at least 40% of the axial width of the crown reinforcement, - the reinforcing elements of the radially outermost working layer forming an angle (α2) with the circumferential direction that is greater in terms of absolute value than the angle (α1) formed by the reinforcing elements of the radially innermost working layer with the circumferential direction, - the absolute value of the difference between the absolute values of the angles (α2) and (α1) eing greater than 7°, - characterized in that the mean angle α satisfies the relationship: 28 + 110 * exp − L / 100 < α < 32 + 110 * exp − L / 100, α being defined by the relationship Arctan((tan(|α1|) ∗ tan(|α2|)) 1/2), L being the maximum width of the tyre measured in the axial direction and expressed in mm, - in that the metal reinforcing elements of said at least one layer of the carcass reinforcement are cords that have a flow rate less than 20 cm 3 /min in what is referred to as the permeability test described in the standard ASTM D2692-98, and - in that a rubber compound is present least locally within the structure of said cords. - said two working crown layers (41, 42) and said at least one layer of circumferential reinforcing elements being the only ones present to form the crown reinforcement over at least 40% of the axial width of the crown reinforcement, - the reinforcing elements of the radially outermost working layer forming an angle (α2) with the circumferential direction that is greater in terms of absolute value than the angle (α1) formed by the reinforcing elements of the radially innermost working layer with the circumferential direction, - the absolute value of the difference between the absolute values of the angles (α2) and (α1) eing greater than 7°, - characterized in that the mean angle α satisfies the relationship: 28 + 110 * exp − L / 100 < α < 32 + 110 * exp − L / 100, α being defined by the relationship Arctan((tan(|α1|) ∗ tan(|α2|)) 1/2), L being the maximum width of the tyre measured in the axial direction and expressed in mm, - in that the metal reinforcing elements of said at least one layer of the carcass reinforcement are cords that have a flow rate less than 20 cm 3 /min in what is referred to as the permeability test described in the standard ASTM D2692-98, and - in that a rubber compound is present least locally within the structure of said cords.