Construction of a car tube tire. As you know, tube tires have an inner tube inside the tire, made of soft rubber, ring-shaped, filled with air. Air is forced into the inner tube through the valve. The forced air flows past the valve stem, moves the valve plate away and inflates the tire tube. The valve spring closes the sliding plate and the forced air cannot escape from the tube. In order to prevent the ingress of dirt, the valve body is closed with a screw-on protective cap. The cap usually has a tip, for screwing and unscrewing the valve insert into the fuselage. The seat of the air valve in the inner tube is reinforced by a vulcanized overlay made of several layers of canvas and rubber. In the tube tires of trucks and buses, there is usually a rubber band between the tube and the rim of the wheel., the so-called. protector, which protects the inner tube from direct contact with the metal rim.