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We compare the half-light circular velocities, V_{1/2}, of dwarf galaxies inthe Local Group to the predicted circular velocity curves of galaxies in theNIHAO suite of LCDM simulations. We use a subset of 34 simulations in which thecentral galaxy has a stellar luminosity in the range 0.5 x 10^5 < L_V < 2 x10^8 L_{sun}. The NIHAO galaxy simulations reproduce the relation betweenstellar mass and halo mass from abundance matching, as well as the observedhalf-light size vs luminosity relation. The corresponding dissipationlesssimulations over-predict the V_{1/2}, recovering the problem known as too bigto fail (TBTF). By contrast, the NIHAO simulations have expanded dark matterhaloes, and provide an excellent match to the distribution of V_{1/2} forgalaxies with L_V > 2 x 10^6 L_{sun}. For lower luminosities our simulationspredict very little halo response, and tend to over predict the observedcircular velocities. In the context of LCDM, this could signal the increasedstochasticity of star formation in haloes below M_{halo} \sim 10^{10} M_{sun},or the role of environmental effects. Thus, haloes that are "too big to fail",do not fail LCDM, but haloes that are "too small to pass" (the galaxy formationthreshold) provide a future test of LCDM.

NIHAO V: Too big doesn't fail -- reconciling the conflict between LCDM predictions and the circular velocities of nearby field galaxies