Using a computerized mechanical pendulum, we have studied the lateral magnetic flux motion of the Bi-based high-T c superconductors in the quasi-static magnetic field (0.1 Hz) for the range 1 μm to 0.35 mm. The effect of d.c. and a.c. transport currents on the flux motion has also been investigated. We argue that the lateral magnetic stiffness is a measure of the pinning potential of the fluxoids in the superconductors. The pinning energy barrier ε is estimated to be about 0.3 eV based on the stiffness measurements, which is comparable with the data from the YBa2Cu3O7-χ superconductors.