Re: Springs never wear out

[Gerry Lehmann <lehmann@domain.elided>]

It is true that the torsional modules for steel (11.25 x 10^6), which is
a critical component of the spring rate equation, never changes.  It is
a material property of steel but there are several other defects that
can shorten the useful life of springs.  Sagging, as mentioned
previously, is probably the most common of these but other issues
involve point fatigue caused by corrosion, or other localized defects
that over work (fatigue) a particular spot and can lead to a change in
effective overall rate or worse (and thankfully less common) mechanical
failure.  In fact sagging can lead to coil bind, which can cause a less
than desirable and inconsistent "progressive" rate.  Coil springs never
change their rate on a material basis but the geometry issues can cause
a real change in effectiveness.

Gerry Lehmann
'86 GTV6 3.0

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