As we all know, if a car happens to be struck by lightning its passengers will probably be safe. The usual explanation is that the tires of the car are insulators. The actual reason, as E&M textbooks stress, is that the surface of the car, being a conductor, acts as a Faraday cage. My question is, why would anyone think that insulating tires protect cars against lightning strikes? To be concrete, suppose that the surface of the car were made of an insulating material and therefore the car didn't act as a Faraday cage. Is there any reason to think that the insulating tires would protect the car? What's the justification behind this belief?