Matching springs to shocks...

I'm sure I know the answer to this, but I'm thinking of dropping the 400lb springs back into the SiR instead of the variable-rate Jamex springs.

Question is, do I need to get a new set of shocks? The Jamex are quite soft - about par with the original SiR springs but with progressive-rate winds on the front as well as the rear. My guess is 280-180lbs

BTW - anyone got the formular for working out the rate? It's diameter, number of coils and height with one or two other things thrown in I think

Try this:
http://www.proshocks.com/calcs/coilsprate.html