Spring Rate

The spring rate is the change of load per unit of deflection. It is typically donated as the number of lbs. per 1 inch of travel. The smaller the spring rate the lighter the feel. There are three ways to determine the spring rate; calculate it, measure it, or ask sales rep. at W.B. Jones Spring. We are always happy to help!

Calculating:

WARNING! This is not a simple math problem. The spring rate is a factor of the type of material, the mean coil diameter, the wire diameter, and the number of coils. Here is the formula for round wire springs.

R= (Gd⁴)/8n_aD³) — again we are always happy to help!

R= Spring rate (lbs/in)

G= Modulus of rigidity of material (psi)

d= Wire diameter (in)

n_a= Number of active coils

D= Mean coil diameter (in)

 

Measuring:

Measuring a spring rate is more straight-forward than calculating. However, you will need special equipment that measures loads. The first step is to deflect the spring about 20% of its available deflection. At this point, measure the load (P₁) and the length (L₁). Next, deflect the spring a bit further, but no more than 80% of its available deflection. Again, measure the second load (P₂) and the second length (L₂).  Make sure the coils are not touching at L_2. Now calculate! R=(P₂ – P₁)/(L₁-L₂).

If you have any questions or need help determining the spring rate of your spring, please do not hesitate to call!