An overload is a par A  t of a leaf spring that engages when the primary part of the leaf spring compresses under load to capture and help maintain ride height. In a two-stage design, it is the bottom leaf that is considerably thicker than the primary leafs above it.  Upper overloads are a single tapered leaf or multi-leaf design that sits spaced up above the primary pack designed to engage onto stopper brackets mounted to the frame. Upper overloads do not contribute to spring rate when vehicle is empty therefore no negative effect on ride quality.