The present invention is a runflat insert comprising: a) an elastomeric outer contacting portion for contacting the interior surface of the tire during deflated operation of the tire, b) a reinforced annular band disposed radially inward of the outer contacting portion, where the band comprises an elastomeric shear layer, at least a first membrane adhered to the radially inward extent of the elastomeric shear layer and at least a second membrane adhered to the radially outward extent of the elastomeric shear layer, c) at least one sidewall portion extending radially inward from the contacting portion for connecting the annular band to a base member fitted around the wheel rim for securing said insert to the rim, and d) at least one carcass layer adhered to the annular band, and the carcass extending radially inward from said annular band and anchored in the base member; where the shear layer comprises an elastomeric composition that includes a metal salt of a carboxylic acid. The shear layer preferably comprises a dienic elastomeric composition that includes a metal salt of a carboxylic acid and is preferably cured with a peroxide curative agent. In one embodiment of the invention, the metal salt of the carboxylic acid is zinc diacrylate or zinc dimethacrylate.