The linear correlations between ground state gyromagnetic ratios and superallowed $\ensuremath{\beta}\ensuremath{-}\mathrm{d}\mathrm{e}\mathrm{c}\mathrm{a}\mathrm{y}$ transition strengths of mirror nuclei are reexamined in the light of more extensive experimental data. Predictions are made for the (as yet unmeasured) ground state magnetic moments of 11 nuclei in the mass range $45l~Al~59,$ using shell model calculations to resolve sign ambiguities. The linear correlations are tentatively extended to superallowed decays between excited states of mirror nuclei.