Tyre in the form of a torus having an internal wall and an external wall, the internal wall being, at least in part, covered with an airtight layer, the tyre having an axis of rotation and comprising: two beads intended to come into contact with a mounting rim, each bead comprising at least one annular reinforcing structure having a radially innermost point, two sidewalls extending the beads radially outwards, the two sidewalls coming together in a crown comprising a crown reinforcement (80, 90), radially surmounted by a tread; a radial carcass reinforcement composed of thread reinforcing elements having an elongation at break EB C and a breaking strength BS C, placed at a placement pitch P C and coated with rubber composition, the carcass reinforcement extending from one bead to the other, passing through the crown, the carcass reinforcement being anchored in each bead by a turn-up around the said at least one annular reinforcing structure, so as to form an outward strand and a return strand, the carcass reinforcement being designed so as to satisfy the inequality: BS C P C ≤ 1.5 ⋅ 10 6 ⋅ R S 2 − R E 2 R T, where BS C is expressed in newtons, R S is the radial distance between the axis of rotation of the tyre and the radially outermost point of the carcass reinforcement, R E is the radial distance between the axis of rotation of the tyre and the axial position where the tyre reaches its maximum axial width, and R T is the radial distance between the axis of rotation of the tyre and the radially innermost point of the said at least one annular reinforcing structure, the placement pitch P C and the radial distances R S, R E and R T being expressed in metres; each sidewall of the tyre additionally comprising an additional strengthening reinforcement composed of thread reinforcing elements having an elongation at break EB A and a breaking strength BS A, placed at a placement pitch P A and coated with a rubber composition, the additional strengthening reinforcement extending between a radially internal end occurring close to the said at least one annular reinforcing structure of the bead which extends the sidewall and a radially external end located radially between the carcass reinforcement and the crown reinforcement, in which EB A, BS A, P A, EB C, BS C and P C are chosen such that BS A P A ≥ 1.3 ⋅ BS C P C, and EB C ≥ EB A, it being specified that the breaking strengths BS A and BS C and the elongations at break EB C and EB A are determined on the reinforcing elements after extraction from the cured tyre, the said airtight layer being, at least in part, covered with a layer of self-sealing product. two beads intended to come into contact with a mounting rim, each bead comprising at least one annular reinforcing structure having a radially innermost point, two sidewalls extending the beads radially outwards, the two sidewalls coming together in a crown comprising a crown reinforcement (80, 90), radially surmounted by a tread; a radial carcass reinforcement composed of thread reinforcing elements having an elongation at break EB C and a breaking strength BS C, placed at a placement pitch P C and coated with rubber composition, the carcass reinforcement extending from one bead to the other, passing through the crown, the carcass reinforcement being anchored in each bead by a turn-up around the said at least one annular reinforcing structure, so as to form an outward strand and a return strand, the carcass reinforcement being designed so as to satisfy the inequality: BS C P C ≤ 1.5 ⋅ 10 6 ⋅ R S 2 − R E 2 R T, where BS C is expressed in newtons, R S is the radial distance between the axis of rotation of the tyre and the radially outermost point of the carcass reinforcement, R E is the radial distance between the axis of rotation of the tyre and the axial position where the tyre reaches its maximum axial width, and R T is the radial distance between the axis of rotation of the tyre and the radially innermost point of the said at least one annular reinforcing structure, the placement pitch P C and the radial distances R S, R E and R T being expressed in metres; each sidewall of the tyre additionally comprising an additional strengthening reinforcement composed of thread reinforcing elements having an elongation at break EB A and a breaking strength BS A, placed at a placement pitch P A and coated with a rubber composition, the additional strengthening reinforcement extending between a radially internal end occurring close to the said at least one annular reinforcing structure of the bead which extends the sidewall and a radially external end located radially between the carcass reinforcement and the crown reinforcement, in which EB A, BS A, P A, EB C, BS C and P C are chosen such that BS A P A ≥ 1.3 ⋅ BS C P C, and EB C ≥ EB A, it being specified that the breaking strengths BS A and BS C and the elongations at break EB C and EB A are determined on the reinforcing elements after extraction from the cured tyre, the said airtight layer being, at least in part, covered with a layer of self-sealing product.