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Spring Rate Calculations

A note about calculating dual spring rates.     

           
When  calculating your dual spring rates we request you complete the following steps with your existing setup and supply the information gathered in this process:-     
           

     Step 1  - Adjust the spring pre-load rings to obtain the required ride height (even if the springs are loose at full extension).;

     Step 2  - With the vehicle at ride height, ensure the crossover ring (if fitted) is not positioned against the spring divider.**

     Step 3  - Measure the overall lengths of each individual spring at ride height (we call this Nominal length).

     Step 4   - Jack vehicle up so wheels are off the ground and suspension is at full droop. 
                    Measure each spring length (We call this Installed length).

     Step 5  - Measure pre-load or how loose the springs are when the wheels are off the ground (positive or negative preload).

     Step 6  - Remove springs from shock. Measure and record the existing rate and length (we call this Free length).

     Step 7  - Record the maximum possible spring length that can be fitted to the shock (we call this Spring envelope).

     Step 8  - Record the thread length of the shock absorber (we call this Thread envelope).

     Step 9  - Record Spring Rates

     Step 10 - Send Information.

.
      **This can confuse how much preload is required to achieve correct ride height.   

 

   
Front
 
Rear
             

Spring Rate

 

Upper:__________lb/in

Lower:__________lb/in

Upper:__________lb/in

Lower:__________lb/in

             
    O/S N/S   O/S N/S
             

Free Length

 

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

             

Installed Length

 

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

 

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

             

Nominal Length

 

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

 

Upper:__________mm

Lower:__________mm

Upper:__________mm

Lower:__________mm

             

Thread Envelope

  __________mm __________mm   __________mm __________mm
Spring Envelope   __________mm __________mm   __________mm __________mm

 

We have the facility to measure spring rates if you cannot identify your existing spring rates.
 
When finished you should have recorded the Free, Installed and Nominal length of each individual spring together with the amount of positive or negative preload and the existing rate.
From this information we should be able to advise on optimum springs for your vehicle.  
 
Alternatively you download this form from Fox's website and fill it in.

N.B. Previoulsy we have offered springs rate calculations as a free service when customers have purchased shocks and springs from us.