Ring-down temporal measurements of silicon-on-insulator wire racetrack resonators are performed with 150 fs input pulses using a parametric process in a nonlinear crystal to gate and amplify the weak output pulses. We measure the cavity round trip time and the quality factor of these all-pass filters and find excellent agreement with continuous wave spectroscopic measurements as well as with an analytic model built using numerical solutions for the fully vectorial waveguide modes.