The HD springs on my SIII are far too stiff for my usage of the vehicle, so I'm looking at how to improve them. At present they are rusty and probably seized, but HD springs with a lightly loaded truck cab will never be that great.

I have many sets of springs, many have issues with rust or wear but I started wondering about combining "good" leaves to get what I want. I have read many articles, including several discussions here, and found many calculations......

It seems that many thin leaves are theoretically more flexible because the differential stretching in each leaf is less than in thicker leaves, but conversely there is more interleaf friction with larger numbers of thinner leaves. So opinion ends up divided on which is better (and why!).

However if I work with what I have, for the rear I could use perhaps 5 leaves from HD springs in combination with the two bottom (flat) leaves from a dual rate set. This would seem (by calculation) to give me something a bit softer than the standard pack, but then increasing in rate when the pack flattens on to the bottom (dual rate) springs.

Alternatively, because droop seems largely dependent on the top leaf, I could use the top leaf from a standard spring pack, 0.25" rather than 0.281" of the HD version, to give slightly (!?) more droop.

Obviously I would need to ensure the lengths of each leaf are long enough to maintain a "uniform" pattern, with no gaps between the lowest "curved" leaf and the "flat" dual rate leaves (the reason, I assume, for the folded leaf on standard dual rate packs?).

Any thoughts?