In this paper, the pre-slip transient behaviour was investigated using three types of rubber material subjected to tangential loading prior to gross slippage or sliding. A special-purpose rig was constructed which has a friction-surface cradle support structure with vertical leaf springs and a normal loading support structure with horizontal leaf springs. A somewhat non-linear increase of tangential shear force with displacement in the transient pre-slip region and distinctive characteristics were obtained for each rubber type. Thickening and thinning of the rubber specimen during sliding depend primarily on rubber hardness.