Spring Rate Calculating InfoSpring 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
