# Racing Formulas: Spring Height, Rate, Deflection & Load

Review the below formulas to properly evaluate spring performance in racing applications, or access our Spring Rate Calculator.

### Solid Height

Solid Height= (Number ofCoils – 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= 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 Spring Rate

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

Combined 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 Spring Rate =
(200×500) ÷ (200+500) = 143