One of the most important methods to increase the bit density is the decrem
ent of head-disk spacing. Recently, the investigation of slider-disk contac
t issues is becoming more and more important because of the continual reduc
tion of the head-disk spacing. This paper develops a probability model to c
haracterize the roughness of the air-bearing surface of a slider and the ro
ughness of a disk surface. Based on the probability theory, the Boltzmann e
quation is modified with the average thin-film theory, and the slider-disk
contact force is calculated by a power law. The tripad slider is selected f
or the simulation under various disk speeds, and the air-bearing force and
the contact force are studied in detail. It is observed that the simulation
results are well coordinated with the experimental results on the Contact
start-stop tester and on the dynamic flying height tester.