There have been several methods developed to measure film thickness, but most are not practical because they require physical disturbances of the material or flow by probe insertion. The tread-deflection measurement system was developed to investigate the transient response of a sliding tire as it encounters a change in free waterfilm thickness. The system is capable of measuring transient deflection changes in the contact region of a tire within one millisecond intervals. The system consists of seven capacitive sensors which are fixed to the inside surface of a tire and control the frequency output of integrated function generators which will accurately measure variable-induced displacements of less than 250 micro-inches. This system provides data in a form which enables evaluation of tire footprint shapes as a function of time for both steady state and transient hydroplaning conditions.