The invention relates to a fluid dynamic bearing system particularly to
rotatably support a spindle motor to drive the disk(s) of a hard disk
drive. The bearing system comprises a bearing sleeve and a shaft
accommodated in a bore in the bearing sleeve and rotatably supported with
respect to the bearing sleeve, the surfaces of the bearing sleeve and of
the shaft, which face each other and are separated by a bearing gap (3)
filled with a bearing fluid, forming at least one first radial bearing
region. According to the invention the diameter of the shaft is chosen
such that the relationship between the bearing distance, i.e. the
distance of the fixing point of the shaft to the first radial bearing
region, and the diameter of the shaft is equal to or less than 0.9, and
that the diameter of the shaft is preferably 3 mm to 5 mm.This provision
causes the resonance frequency of the bearing to shift to a higher,
uncritical frequency range.