primary spring /rpm change

[justinator]

Is there a rule of thumb for rpms and spring force?? What I mean is lets say a guy needs 300 rpm more out of a set of weights and he wants to change springs to do so, how much more force does he need......20lbs is equal to how many rpm??

 

[BADSLED]

I can't see how a spring with 20lbs. of more full shift will yield 300rpm at full shift. Turk or Srxpec should may chime in to give you a more accurate estimate.