The tensile behavior of the spoke is a classical Hooke's law response: s = E e. The spoke stress is the applied force divided by the spoke cross-section area.

For a spoke of 300 mm length and 2 mm diameter, the cross sectional area is 3.14 x 10^-6 m^2.. The yield stress for stainless steel is about 400 MPa.

If the spoke is to be loaded to half the yield stress in fabricating the wheel, a force of about 630 N must be applied to the spoke. The Young's modulus, E, for the steel is 210 GPa, and from Hooke's law, the spoke extension expected by the application of the pre-load force is about 0.29 mm.

From: McMahon & Graham, "The Bicycle & the Walkman,"
Merion (1992)