In one embodiment, a pneumatic tire having a built-in 
sealant layer, before cure, includes an unvulcanized pneumatic tire 
assembly having an outer circumferential rubber 
tread and a supporting carcass. A precursor 
sealant layer is situated between the supporting carcass and an innermost rubber inner liner. The precursor 
sealant layer includes a non-flowing 
polyurethane composition that is neither gel-like nor tacky and is self-supporting. The precursor sealant layer, during curing of the unvulcanized pneumatic tire 
assembly, thermally degrades so as to provide a gel-like and tacky, self-healing 
polyurethane composition which defines the built-in sealant layer. The resulting tire, with its innermost 
polyurethane composition, allows for 
elimination or reduction in blister formation by reducing or 
elimination the amount of gases typically given off by organoperoxide-butyl based sealant 
layers, such as when the tire is at its running temperature. Consequently, the thickness of the inner liner may be reduced.