There are provided a pneumatic radial tire of heavy load vehicles, in which durability of a belt is improved. The audio amplifier controls a delay time lasting until the audio responsive to the received audio data is outputted so that the delay time matches the aforementioned delay time. and has at least two epoxy groups in a molecule. The CPU brings about a switching state in which an image forming region lies between a primary transfer position on the most downstream one of the photosensitive drums and a secondary transfer position and in which non-image forming regions simultaneously lie at the primary transfer position and at the secondary transfer position.