When a rotating shaft is supported by single-row deep groove ball bearings with "angular clearances", there appear rotating anisotropies both of shaft stiffness and of nonlinearity which are induced by imperfections in rotating parts. We have already reported about the particular vibration phenomena at the major critical speed in the case where unsymmetrical nonlinear characteristics appeares more strongly than symmetrical ones. In this paper, we try to clarify the effects of symmetrical nonlinear characteristics on the resonance curves in such case. Furthermore, we deal with the case experimentally and analytically where symmetrical nonlinear characteristics appear more strongly than unsymmetrical ones. In this case, a particular shape of resonance curve appears at the major critical speed, and this resonance curve changes its shape depending on the angular position of the unbalance.