Failure of a retaining snap ring application can result from failure of the ring itself, failure of the groove, or both. If a ring fails, the cause is likely to be from shearing of the ring. Shear failure occurs when a ring is installed in a groove and loaded by a retained part with both the groove and the retained part having a compressive yield strength greater than 45,000 psi (310 MPa); or when the load is applied through a retained part and groove, both having sharp corners and line-to-line contact; or when the ring is too thin in section compared with its diameter.

P_s = ( π D t S_s ) / K

Where:

P_s = Thrust force ( lb_f, N ),
D = Shaft or housing diameter (in, mm),
t = Retaining ring thickness (in, mm),
S_s = Shear strength of the retaining ring material (lb/in², N/mm²)
K = Factor of safety