An apparatus is disclosed for flatproofing a tire and wheel assembly with
a flexible, lightweight foam-fill by supplying at least two polyurethane
reactive materials to a static mixer. The static mixer mixes the
reactants, and a nucleating gas is supplied to the mixed reactants in the
static mixer to form a liquid reactant mixture with entrained gas. The
reactant mixture is injected into the tire and wheel assembly where the
mixture reacts and foams replacing the air in the tire with a flexible,
lightweight semi-open cell foam-fill. The foam-filled tire and wheel
assembly is then allowed to cure.