You can calculate spring rate according to the dimensions of the spring.

K=(d4G)/(8D3Na) (the four and the three are supposed to be superscripts)

Where d is the wire diameter, D is the coil diameter, Na is the number of active coils, and G is the shear modulus of the material. The shear modulus for spring steel should be about 11.5 million psi if I'm doing my math right. The number of active coils depends on the end treatment of the spring. I forget what suspension springs usually have for end treatments.

Na=Nt-1 for plain-ground ends

Na=Nt-2 for squared or squared-ground ends

Nt is the total number of coils in the spring.

__________________
Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.