Support assembly for movable, rotating or sliding shafts, having a bearing unit adapted to receive the movable shaft, a casing and a cover for fluid sealing an opening of an internal seat of the casing; the bearing unit having a radially outer ring, a radially inner ring and a row of rolling elements between the radially outer ring and the radially inner ring; the support assembly also being provided with: a rear sealing device, placed on the opposite side with respect to the cover, and comprising a metal shield and a vulcanized rubber liner equipped with a first, axially outer, sealing lip and with a second, axially inner, sealing lip the support assembly being characterized in that the rear sealing device comprises a further third sealing lip slidingly contacting the radially inner ring.