Run-flat tire having an additional sidewall reinforcement

1. A run-flat tire comprising:

a crown comprising a crown reinforcement surmounted by a tread;

two sidewalls extending the crown radially inward;

two beads radially inward to the sidewalls and each comprising an annular reinforcing structure;

at least one carcass reinforcement anchored in each of the beads and extending from the beads through the sidewalls toward the crown; and

at least one sidewall insert axially on the inside of the carcass reinforcement, comprising at least one polymer compound;

wherein at least one sidewall of the tire further comprises:

(i) at least one additional sidewall reinforcement having radial ends and comprising radial reinforcing elements, positioned axially on the outside of the carcass reinforcement, a radially inside end of said radial ends of the at least one additional sidewall reinforcement being, in any radial section, radially on the inside of an axial straight line that passes through those points in the sidewalls at which the carcass reinforcement has its greatest axial width when the tire is mounted on a rim; and

(ii) a layer of polymer compound positioned between said at least one additional sidewall reinforcement and the carcass reinforcement, over at least a portion of the additional sidewall reinforcement,

wherein a radially outside end of the additional sidewall reinforcement is axially on the outside of an adjacent axial end of the crown reinforcement,

wherein a maximum axial thickness of the layer of polymer compound positioned between said at least one additional sidewall reinforcement and the carcass reinforcement is greater than or equal to 10% of a maximum axial thickness of the sidewall of the tire in a radial region over which said at least one additional sidewall reinforcement extends,

wherein an axial distance between at least one of the radial ends of said at least one additional sidewall reinforcement and the carcass reinforcement is less than 2 mm, and

wherein the maximum axial thickness of the layer of polymer compound positioned between said at least one additional sidewall reinforcement and the carcass reinforcement is greater than or equal to 2 mm.

2. The tire according to claim 1 , wherein said at least one additional sidewall reinforcement consists of two separate portions, said portions being positioned in different sidewalls.

3. The tire according to claim 1 , wherein a radial distance between the radially outside end of each said portion of the additional sidewall reinforcement and the axial ends of the crown reinforcement is greater than 6 mm.

4. The tire according to claim 1 , wherein a radial distance between the radially inside end of said at least one additional sidewall reinforcement and a radially innermost point of the corresponding annular reinforcing structure is greater than or equal to 20 mm.

5. The tire according to claim 1 , wherein an axial distance between at least two radial ends of said at least one additional sidewall reinforcement and the carcass reinforcement is less than 2 mm.

6. The tire according to claim 1 , wherein the composition of the polymer compound positioned between said at least one additional sidewall reinforcement and the carcass reinforcement is identical to the composition of the polymer compound of the sidewall insert.