Spring Rate Calculating Info

Spring Height, Rate, Deflection, & Load Formulae

Question:

Do you have a list of useful equations for performing spring calculations?

Answer:

Yes, we do! Below you will find various formulae that racers have used to evaluate performance of different configuration options.

Solid Height

Solid Height = (Number of Coils – 0.25) x Wire Diameter

For example, for a spring with 14 coils and a wire diameter of 0.5”, the Solid Height would be calculated as follows:

Solid Height = (14 – 0.25) x 0.5 = 6.875

Rate

Rate = Load (lbs.) ÷ Spring Deflection (in.)

For example, if a spring deflects by 2.75” under a load of 300 lbs, the Rate would be calculated as follows:

Rate = 300 ÷ 2.75 = 109

Deflection

Deflection = Load (lbs) ÷ Rate

For example, a spring under a load of 300 lbs with a 109 Rate, the deflection would be calculated as follows:

Deflection = 300 ÷ 109 = 2.75

Load

Load = Deflection x Rate

For example, a spring with a 109 Rate and a 2.75” deflection, the load would be calculated as follows:

Deflection = 2.75 ÷ 109 = 300

Combined(Primary) Spring Rate

This is used when two springs are stacked on top of each other.

Combined(Primary) Spring Rate = (Spring Rate 'A' x Spring rate 'B') ÷ (Spring Rate 'A'+Spring Rate 'B')

For example if the rate for spring 'A' is 200 and the rate for spring 'B' is 500, the combined rate is calculated as follows:

Combined(Primary) Spring Rate = (200*500) ÷ (200+500) = 143