runflat tires are generally made by including a stiff insert in the sidewall thereof . this insert should be as stiff as possible to help support the weight of the vehicle to which the tire is mounted in situations where there is a loss of air pressure . during periods of operation after loss of air pressure the stiff insert carries most of the load on the tire which leads to the generation of heat . heat build - up can then lead to thermal degradation in the insert . a reduction in crosslink density and a change in the distribution of crosslink types is the result of this thermal degradation . this invention is based upon the discovery that thermal degradation in the inserts of runflat tires can be reduced by including a 1 , 6 - bis - hexane therein as an antireversion agent . this invention more specifically discloses a pneumatic tire having at least one insert to provide the tire with runflat capability wherein the insert is comprised of a rubbery polymer and 1 , 6 - bis - hexane .