The short answer is that this can be done, and, in fact, there are kits available to allow you to add a leaf to a suspension spring-pack. The broad idea is to make the spring stiffer, increasing ...

We aren't huge fans of big lift blocks thatgo under leaf springs on top of axle spring pads, and Off Road Design not only agrees but has a better option with what they call a Zero Rate add-a-leaf.

It is said that the leaf-spring suspension is the oldest suspension used for automobiles. The leaf-spring system was used more recently in '70s production cars, some of which are still in service ...