A pneumatic insert for a pneumatic tire comprises a generally toroidal-shaped hollow member having a pair of annular insert beads with sidewalls extending therefrom joined to an insert crown portion. Each insert bead has a foot portion with a projecting elastomeric formation at the bead heel to furnish an inner bead diameter at the heel that is less than the inner bead diameter at the toe.In at least one embodiment of the invention the bead heel projection is of triangular shape with a vertex of the triangle defining the first inner bead diameter.In another embodiment of the invention the projecting elastomeric formation extends axially away from the bead heel in a direction substantially parallel to the bead foot.