How to determine spring rate

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  1. Determining Travel:
    It is recommended that there be approximately 3" of compression travel available (including the bumpstop). This means the chassis must be supported by a spring rate that will allow the chassis to be supported 3" upward from the bottoming position
  2. Determining the Vehicle Sprung Weight:
    Establish front and rear weight of the vehicle. Establish unsprung weight. This is the weight not supported by the springs. i.e., tires, wheels, wheelie bars, brakes, and 1/2 of the weight of the shock, spring, driveline, and ladder bar or four link. 1/2 the weight is used for some components because their weights are equally shared between sprung and unsprung weight. Determine spring weight, that is the weight of the vehicle less the unsprung weight.
  3. Determining Spring Rate:
    Divide the rear sprung weight by 2 to determine the load for each rear corner. Divide the front sprung weight by 2 to determine the load for each front corner. If the load for the rear corners is 330 lbs. each(660 lbs./2 = 330 lbs.) then divide the 330 lbs. by the compression travel needed and you arrive at the base spring rate of 110 lbs. per inch. Ex: 330 lbs./3" compression travel = 110 lbs. spring rate.