Gamow-Teller (GT) transitions can be studied in both beta decay and charge exchange (CE) reactions. If isospin is a good quantum number, then the T-z = -1 -> 0 and Tz = + 1 -> 0 GT mirror transitions, are identical. Therefore, a comparison of the results from studies of beta decay and CE should shed light on this assumption. Accordingly we have studied the beta decay of the Tz = -1 fp-shell nuclei, Ni-54, Fe-50, Cr-46, and Ti-42, produced in fragmentation and we have compared our results with the spectra from (He-3, t) measurements on the mirror Tz = +1 target nuclei studied in high resolution at RCNP, Osaka. The beta decay experiments were performed as part of the STOPPED beam RISING campaign at GSI.