There was some discussion about this topic a while ago. I had
tried to re-temper some sagging springs with a disastrous
result (12 months later they were twice as bad!).
Last week I took a set of old sagged springs with a couple of broken
leaves to a local spring maker that was recommended to me by
a farming machinery place.
It turns out that they no longer manufacture the basic material in
the thickness originally used in spridget leaves, so he made a new
main leaf out of 8mm stuff. He cut the eyes of the old main and used
that as #2. He picked and chose out of all the remaining leaves to
make a new symmetric set, re-arched the lot at 2" lower than stock.
I still have to fine tune the ride height (by removing some of the minor
leaves
or at worst re-arching them again) but the result is terrific. He tells me
that the
main leaf represents 80% or so of the spring stiffness. Using a stiffer main
has given me a very stiff rear spring (which I wanted on my racecar) but has
also dramatically reduced the tendency to 'tramp' or windup the spring under
power. They have slightly improved the lateral location of the axle too.
Once I get the ride height correct, I'll post a summary of the final setup.
The whole job cost me A$150 or just on US$100, much less than new springs
from the UK!!! On top of that, they are much less likely to sag because
of the thicker main.
Mike
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