This work presents a model to assess the equivalent load for self-lubricating radial spherical plain bearings under combined loads, based on the study of the interference field. Using an algorithm based on the model, a methodology has been created to estimate failure load combinations. The results, validated via Finite Element Analysis, are presented in the form of load magnification factors for equivalent load assessment, which prove to be similar to those provided by manufacturer catalogues. The contribution of this work lies in explaining the technical background of these factors, not explained in any catalogue or standard, further developing a methodology that will enable any manufacturer to generate the values for their particular products and design parameters.