How To Calculate New Preload And Springs By Using Existing Springs

If you’ve found that your coilover springs have the wrong rates, this article will guide you through the process of taking the necessary measurements so we can calculate the correct rates. Spring rates and preload are not one-size-fits-all; we tailor your rates to suit your ride and the terrain you’ll be tackling. If you plan to purchase new springs through AccuTune Offroad, please use our Spring Swap Form to help with this process.

Initial Coilover & Spring Setup:

Starting with the correct setup is crucial, as inaccurate measurements won’t provide meaningful results.

  • Charge shocks to proper pressure
  • Dual rate nuts are not in use at ride height
  • Bump stops not contacting chassis at ride height
  • Vehicle is at desired ride height

Contact us for calculating new spring rates if you aren’t able to achieve proper ride height with your current springs.

Three coilover spring scenarios:

Scenario 1: Springs are tight at full droop (Positive Preload)
Scenario 2: Springs are loose at full droop, without tender coils or triple rate springs (Negative Preload)
Scenario 3: Springs are loose at full droop, with tender coils that are always tight (Negative Preload With Helper Springs)

1: Positive Coilover Spring Preload:

With vehicle sitting at ride height:

  • Measure shock shaft showing (pretend like bottom out bumper doesn’t exist)
  • Measure coilover threads showing above spring adjuster
  • Record upper and lower spring rates

With vehicle at full droop:

  • Measure shock shaft showing
  • Loosen spring adjuster nut until springs start to rattle
  • Measure coilover threads showing above spring adjuster

The amount you’ve moved the spring perch determines the positive preload. Share the measurements with us, and we’ll calculate the appropriate spring rates for you.

2: Negative Coilover Spring Preload (Loose Springs, No Tender Coil):

With vehicle at ride height:

  • Measure shock shaft showing (pretend like bottom out bumper doesn’t exist)
  • Measure coilover threads showing above spring adjuster
  • Record upper and lower spring rates

With vehicle at full droop:

  • Measure shock shaft showing
  • Tighten spring adjuster nut until springs stop rattling
  • Measure coilover threads showing above spring adjuster

How much you moved the spring perch is how much NEGATIVE preload you have.
Call us with the measurements and we will calculate new spring rates.

3: Negative Coilover Spring Preload (Loose Springs, WITH Tender Coil):

With vehicle at ride height:

  • Measure shock shaft showing (pretend like bottom out bumper doesn’t exist)
  • Measure height of tender coil
  • Record upper and lower spring rates

With vehicle at full droop:

  • Measure shock shaft showing
  • Measure height of tender coil

The distance the tender coil expanded is how much NEGATIVE preload you have.
Call us with the measurements and we will calculate new spring rates.

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