Variable-stiffness wedge insert for runflat tire

A pneumatic radial ply runflat tire having a tread, a carcass comprising at least one radial ply and two bead regions and two sidewalls each reinforced by at least one insert, a belt structure between the tread and the carcass, the tire characterized by:

• each insert having an elastomeric porous section located at the axially-inner portion of the insert, the elastomeric porous section being embedded into an elastomeric stiffer layer which constitutes the remainder of the insert;
• the elastomeric porous section is a closed cell porous elastomer or thermoplastic elastomer;
• and
• the porosity of the porous sections is between 10 and 40 percent elastomer and the remainder gas.

A pneumatic radial ply runflat tire having a tread, a carcass comprising at least one radial ply and two bead regions and two sidewalls each reinforced by at least one insert, a belt structure between the tread and the carcass, the tire characterized by:

• each insert having an elastomeric porous section located at the axially-inner portion of the insert, the elastomeric porous section being embedded into an elastomeric stiffer layer which constitutes the remainder of the insert;
• the elastomeric porous section is a closed cell porous elastomer or thermoplastic elastomer;
• and
• the porous section has a compressive modulus of between 3 MPa and 10 MPa as the section is squeezed and a compressive modulus of between 15 MPa and 80 MPa when the porous section has collapsed.