To find your rear (or front) spring rate (the simple way)
1 Measure rear (or front)ride height (both sides should be equal)
2 Put a weight in the car (centre on line between rear(or front) suspension turret tops)
3 Measure rear(or front) ride height again (both sides should have dropped the same amount, if not your weight is not central or you have a weak or broken spring)
4 The wheelbase and distance to weight is within a centimeter or so close enough to be a constant of 1,as 2475mm divided by 2475mm = 1
5 Now multiply the weight by 1 I.E.50 kilos = 50 or 100 kilos =100
6 Now divide the weight in kilos by the drop in ride height (from one side only) (example weight = 100 kilos divided by the drop in ride height say 3 centimeters drop – so its 100 divided by 3 which equals 33.3kilos per centimeter), to convert to pounds per inch multiply the answer by 5.588, in this case 33.3 x 5.588 = 186.0804 or 186 pounds per inch, while not rocket science this method should be accurate to 1% or so.
7 For the front wheels, measure the front ride height then place the weight over the front wheel centres, remeasure front ride height then do the same calculations for the front as you did at the rear , ps the fronts will need a lot more weight as the springs are stronger. chris