8.2.1.2 The original dimensions of the spring shall not
change due to fatigue by more than 0.3 mm (0.01 in.) after it
has been mounted in the compression device, compressed
under a force of 1.8 kN (400 lbf), and heated in the oven for
one week at 70°C 6 2°C (158 6 3.6°F). In ordinary use, a
weekly check of the dimensions shall show no greater change
than this over a period of 1 year.