The best way to tell is to take the springs to a suspension shop, and have them put on a spring tester. That will determine what their rate
really is right now, rather than the rate that the manufacturer thought they were going to be when they were new.
You can approximate that yourself, with a scale and a ruler. Set the spring up (on a board to distribute the load) on the scale. Measure the "free length", and note the weight of the spring. Then put a whole bunch of weight on it--you can lean on it. Note how much more weight you've put on it, and the new height of the spring. Finally, put a whole bunch of weight on the spring--if you've got good balance, stand on it. Note the weight and the length.
Just divide the lbs of weight you put on the spring (remember to subtract the spring's own weight from the total) by the number of inches of compression. That should get you lbs/in, which is the spring rate.
Take lots of measurements, to help reduce the impact of errors.
--DD
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Pelican Parts 914 Tech Support
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