We present a study of the frictional properties of microscopic contacts (radius ~ 1 µm) in the high-speed regime (> 1 m/s) during the initiation of full slip. Energy dissipation, lateral contact stiffness, and amplitude of motion are measured for a transverse-shear quartz resonator in contact with a small spherical probe. Averaged values for the elastic and dissipative forces are derived as functions of shearing amplitude, at constant normal loads in the range from 10 µN to 8 mN. We observe a transition from partial to full slip at a threshold amplitude of motion, characterized by a maximum elastic force. Kinetic friction in the full-slip regime is observed to be about a factor of two smaller than this elastic force limit. Data from tests at various normal loads can be collapsed onto common curves by normalizing the forces and amplitudes according their characteristic values. We discuss the observed scaling of these frictional parameters with the size of the contact and the extent of agreement with current theories of microslip.