  Coulomb displacement energies of $T=1/2$ mirror nuclei have been studied via
a series of high-precision $Q_\mathrm{EC}$-value measurements with the double
Penning trap mass spectrometer JYFLTRAP. Most recently, the $Q_\mathrm{EC}$
values of the $f_{7/2}$-shell mirror nuclei $^{45}$V
($Q_\mathrm{EC}=7123.82(22)$ keV) and $^{49}$Mn ($Q_\mathrm{EC}=7712.42(24)$
keV) have been measured with an unprecedented precision. The data reveal a
16-keV ($1.6\sigma$) offset in the adopted Atomic Mass Evaluation 2012 value of
$^{49}$Mn suggesting the need for further measurements to verify the breakdown
of the quadratic form of the isobaric multiplet mass equation. Precisely
measured $Q_\mathrm{EC}$ values confirm that the pairing effect in the Coulomb
energies is quenched when entering the $f_{7/2}$ shell and reaches a minimum in
the midshell.
