Modern auto racing helmets almost always have an outer shell made of rigid carbon fiber, sometimes with an inner shell of thin polystyrene foam and sometimes with spikes that must constantly be in close contact with the rider's skull or face. There are many major differences which make both kinds of helmets often not interchangeable:
A major difference between the two kinds of auto racing helmets is the safety features incorporated into them. With the former, there are additional safety features added to help keep auto racers safe. Carbon fiber auto racing helmets are equipped with additional ventilating systems and extra padding around the ears. Some are even equipped with added heat sources to add even more warmth to the bones.
The other main difference between these two helmets is that, in the case of the latter, there is a visor added to it. Most motorcycle riders do not wear visors while they are on their bikes. However, auto racing helmets, which do not have visors, must have safety features such as shatterproof visors, shatter resistant safety glass, and the like. A visor also protects the ears from debris and flying dirt and mud. This does not mean that all auto racing helmets visors have to be shatterproof or heat-resistant.
The main safety feature in an auto racing helmet is the clear visor. This consists of a thin sheet of plastic, foam, or any other material which can be molded into an elastic tube. This tube can then be fitted to the top of the helmet just below the eyebrows so that the clear visor itself stays in place. In the event of an impact, the foam will effectively absorb the energy and this will minimize the force of the blow on the user's skull.
In addition to the visor, most auto racing helmets also come with side-impact crash protection, windscreen safety locks, and crash pads. These safety features are designed to protect both the driver and any passenger from impacts to the sides, rear, and front of the car. These crash pads are placed on the inside of the vehicle on either side of the driver's seat. If a crash happens during a race, the windscreen safety locks will hold the vehicle upright. In case of a side impact, the windscreen safety locks will help to prevent the vehicle's wheels from being spun out of their tracks.
Another essential feature of auto racing helmets must have by law is a chinstrap. This chinstrap is strapped around the user's chin and mouth, securing them in place. This is necessary because it helps to limit air flow through the helmet and chinstrap will ensure that the helmet does not fly off into the crowd or worse hit a passerby. Auto racing helmets must also be certified by the Department of Transportation. The DOT will inspect the helmets and test their strength and protection against impact. Helmets will also need to meet certain size and weight requirements.