To achieve the areal density of 1 TB/in2 in hard disk drives (HDDs), the magnetic spacing between the slider and disk needs to reduce to 1 nm or smaller. At such small clearance, the contact between the slider and disk is inevitable. Slider-disk contact may induce a drastic slider response, which has a significant negative impact on the reading/writing performance. In this paper, the effect of a low-frequency vibration in the Z-direction (out-of-plane) brought by the tip of gimbal (TG) on slider dynamics is studied. The impacts of three different excitations on the TG resonance are explored. Under such excitations, the bending mode of TG can be easily excited, which consequently induces the vigorous slider vibration. The influences of the air-bearing stiffness on slider dynamics subject to TG mode are also studied. A slider designed with weaker air-bearing stiffness will suffer a stronger TG resonance than that of stiffer air bearing. These experimental and simulation results show that better TG design and more strict environmental or excitations control are required to achieve a robust head disk interface (HDI).