The present invention relates to a protector shield for at least one sidewall of a motor vehicle tire, and to a wheel assembly for a motor vehicle incorporating this protector shield. The invention particularly but non exclusively concerns the fire protection against flames and/or said flammable substances, such as oil or Molotov cocktails, as well as a high solvent and/or acid resistance, especially in hostile environments. A protector shield of the invention is in a form of a curved ring designed to be mounted on a wheel rim receiving said tire and, according to the invention, the shield includes a fire protection part which defines an outer convex face of said shield and which comprises a cross-linked rubber composition which particularly exhibits flame retardant and heat resistance properties for imparting to said tire an improved fire protection against flames and/or flammable substances.