Overload springs, also known as helper springs, are an additional set of springs attached to the existing leaf springs. The overload leaf spring AKA “the muscle,” is designed to help the vehicle when it becomes weighed down while towing or hauling something heavy such as a truck camper or a trailer. When the vehicle, like a truck, is loaded down with a heavy weight, the rear begins to sag slightly. As the rear begins to sag it forces the lower overload leaf spring to come into contact with the other leaf springs above it. Once the truck sags enough, most often several inches, the overload leaf springs begin to touch, and this begins to put the muscle into action.