Abstract: A bearing unit for pinions, in which a pinion is rotatably supported through the bearing unit from the bearing unit itself. The pinion is mounted projecting from the bearing unit. The bearing unit is provided with a single outer ring with two raceways, an inner ring defined by a spacer and by two half-rings disposed on opposite sides of the spacer axially aligned with each other and each having a respective raceway. Two rows of balls are arranged inside of the raceways, where the diameters both of the rows of balls, and the balls themselves are different from each other depending on the proximity or otherwise of the row to the head of the pinion.