Measuring Fork Spring Rate Trick

[toadl]

I've bought a few used bikes and knowing what the spring rate is in the forks and shocks has always been important to me. I came up with this trick, and I am surprised with how accurate it is.
For the fork springs I remove the forks. Remove the small air bleed screw on the fork cap and place the bottom of the forks in a clamp to keep them vertical and balanced.
Measure the distance from the bottom of the fork to the seal with the forks extended all the way until there is no pressure on the spring.
Then, measure the distance from the bottom of the fork to the seal with the forks with a weight on top of the forks. I used an Olympic 45lbs. weight which ways 20.4 KG, bounce the weight a little to overcome friction.
Figure the difference in length. On my 4357 WP forks from my 2003 EC250 the difference was 2.25of an inch or 57.15 mm.
To figure the spring rate KG / mm divide the mass of the weight by the difference in fork length in mm. For me it was 20.4 kg divided by 57.15, which equals .356 kg/mm.
This seems a little light for even stock springs. Usually in the past the numbers have been with in a .01 kg/mm so I believe they are just light springs.
I'm thinking I will have to go up to .44 kg/mm springs for my 200lb body on the EC250. but that seems like a big jump. Maybe I'll try .42 for woods riding.
Hope this can help someone in the future.