Synchronised belt drive

The drive has retaining elements (7, 8) including a radial curved retaining area and formed by an inner wall of a drive housing (4). The retaining elements are completely or partially arranged over a segment of enlacement curves (alpha, beta) of synchronous belts (3) and over belt backs with a radial distance (delta R) that is smaller than teeth depth of the synchronous belts. Driving and driven synchronous belt pulleys (1, 2) include circulating decompression grooves (6.1, 6.2) running through a tooth profile of the pulleys.