Wire Diameter,Number of coils and Spring diameter all have a part to play when determining spring rates.
Thicker Wire = stiffer spring
Fewer Coils = stiffer spring
Smaller Coil Diameter = stiffer spring.
Madslammer, We used modified Datsun 240K springs to make 6Kg springs for a xE38.
KE25 w/Turbocharged, Injected & Intercooled 7K.... The OTHER 1.8!