A hopper box for a heavy lift truck such as mining trucks that minimizes the height of the gravity center of the load includes sheets that generate a floor, a front wall and two side walls. The sheets includes at least one sheet having a first longitudinal concave curved portion as a floor which continues with a longitudinal upper elongated portion which comprises the front wall thereby generating a single longitudinal curved, collapsed and elongated C-shaped sheet. A multiple number of such sheet may be provided and are placed in a juxtaposed manner until reaching the width by incorporating two side walls having on its lower face two longitudinal rigid U-shaped beams, wherein are also included half-round cross stiffeners on its ends.