Leaf spring design is really intricate and it will act as shock absorber in vehicles (Medium -Heavy)
Leaf spring load calculation can be done by applying UTM by fixing the leaf spring in the inverted direction and apply load on bolt area ( The fixing Bolt) we have to take the elongation and the how much or load it is carrying . for each vehicle the disgn will differ . If medum and thin deisng of leaf spring will give good cushioning effect. The camber and CRS of the leaf spring will decide its load carrying charcter ( camber is the distance measured vertically from the center line of The Eyes of the Leaf spring
In vehicle Empty weight (No load condition) the CRS distance of the spring will be less than the loaded vehicle. suppose the CRS distance of the Front wheel and the rear wheel will differ after loading .The distance elongation will ease the vehicle to accomodate the Axels different location while the vehicle absorbs shock or sudden load.