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How To Calculate Springs Rates on a Dual Rate Coilover

Updated: Apr 8, 2023

Calculating spring rates for a dual rate coilover involves determining the stiffness of the two springs used in the coilover. Here is a general process basics guide for calculating spring rates for a dual rate coilover:





  1. Determine the total weight of the vehicle: This includes the weight of the vehicle, passengers, and any cargo.

  2. Determine the unsprung weight of the vehicle: This includes the weight of the wheels, tires, and any other components that are not supported by the suspension.

  3. Determine the target ride height: This is the desired height of the vehicle's chassis above the ground when the suspension is fully compressed.

  4. Determine the compression and rebound stroke of the suspension: This is the distance that the suspension travels when it is compressed and rebounded.

  5. Calculate the first spring rate: The first spring rate should be chosen to handle the majority of the vehicle weight and provide good ride quality. The first spring rate can be calculated using the following formula:

First spring rate ( Upper Tender Spring) = (Vehicle weight - Unsprung weight) / (Compression stroke * Compression ratio)


where:

  • Compression ratio = (Full extended length - Ride height) / Full extended length

  1. Calculate the second spring rate: The second spring rate should be stiffer than the first spring rate and should engage when the suspension is compressed further. The second spring rate can be calculated using the following formula:



Second spring rate ( Lower Heavy Spring ) = ((Vehicle weight - Unsprung weight) / (Compression stroke * Compression ratio)) * (1 - Compression ratio)

  1. Choose the spring rates: The first spring rate and the second spring rate should be chosen based on the desired ride quality and performance of the vehicle. The first spring rate should provide good ride quality, while the second spring rate should be stiff enough to prevent bottoming out during hard impacts.

What is Compression Ratio and how does it affect Coilover Spring Rates?


The compression ratio is a ratio used to calculate the spring rate for a dual rate coilover suspension system. It is the ratio of the compressed length of the suspension to the total extended length of the suspension.




The compression ratio is used in the calculation of the first spring for a dual rate coilover suspension system. The compression ratio is used to determine the amount of compression that the first spring will experience when it is supporting the weight of the vehicle.


The compression ratio can be calculated using the following formula:

Compression ratio = (Full extended length - Ride height) / Full extended length

where:

  • Full extended length is the length of the coilover when it is fully extended.

  • Ride height is the desired height of the vehicle's chassis above the ground when the suspension is fully compressed.

For example, if the full extended length of the coilover is 14 inches and the desired ride height is 10 inches, then the compression ratio would be:



Compression ratio = (14 - 10) / 14 = 0.2857 or 28.57%


The compression ratio is an important factor in determining the spring rate for a dual rate coilover suspension system. It affects the performance of the suspension system, including the ride quality and handling characteristics of the vehicle.


It is important to note that calculating spring rates for a dual rate coilover can be a complex process and requires knowledge of suspension design and engineering principles. It is recommended to consult Carbon Shock Technologies directly or a suspension expert for assistance in calculating spring rates for a dual rate coilover.


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