We present a comprehensive study of generation and collision of optical similaritons in sub-micron silicon photonic wire waveguides. Our analysis of optical pulse dynamics in such wave guiding devices is based on a rigorous theoretical model that incorporates all of the relevant linear and nonlinear optical effects, including modal dispersion, free-carrier dispersion and absorption, self-phase modulation, two-photon absorption, frequency dispersion of the optical nonlinearity, and the free-carrier dynamics. In addition to the particular characteristics of the generation of optical similaritons in silicon photonic wires, we also investigate the dependence of the efficiency of this optical process on the physical parameters and temporal profile of the input pulse. The collision of optical similaritons that propagate both in the normal and anomalous dispersion regime is also analyzed. Guided by the target applications of our study, we considered two technologically relevant spectral regions, namely, telecom and mid-IR frequency domains.