Modulus of Elasticity is the measurement of stiffness and rigidity of spring material, or its elastic ability. The higher the value (modulus), the stiffer the material. Conversely, materials with lower values are more easily bent under load. For most steels and age-hardenable alloys, the modulus varies as a function of chemical composition, cold working and degree of aging. Variation between different materials is usually small and can be compensated for by adjusting the different parameters of the spring, i.e., diameter and active coils.

The following types of Modulus apply to spring design:

MODULUS IN SHEAR OR TORSION (G)
This is the coefficient of stiffness for extension and compression springs.

MODULUS IN TENSION OR BENDING (E)
This is the coefficient of stiffness used for torsion and flat springs (Young''s Modulus).

The Modulus (G) for extension springs and compression springs deals with "shear or torsion" where the Modulus (E) for torsion springs addresses "bending". While this may sound opposite, one should know that when extension and compression springs are extended or compressed, the wire is being twisted (torqued) under load where with torsion springs the wire is being bent.

-The 19th China (Guangzhou) Int’l Spring Industry Exhibition