Previous owner did the springs of my car. I've owned it 15 years, no sag yet. However the back end is quite high so it could sag a little and I would never know!
I would agree with 4406bbl's comment on add-a-leaf length. I did them on my jeep and it gave the lift I wanted but a short helper leaf will induce an s-bend in the main leaf if it's already weak.
Mick, that spring shop fed you a line.
They effed them springs up for you when they re-arched them.
"Spring steel" is beyond my understanding of Metalurgy, but it's a special metal treatment and tampering with it either by cold bending or hot bending ruins them.
IMO there's some truth to it. Leaf springs are made out of a variety of different grades of steel, each with its own heat treating and tempering requirements. A spring shop has no way of knowing what they're working with in terms of both the grade of steel and how close the chemical composition comes to actually meeting the specification for the grade of steel it is supposed to be according to the manufacturer.
