The functional relationships of industrially interesting variables such as pyrolysis temperature, heating rate, and sample size with pyrolysis time were explored to provide basic information on designing energy efficient processes. Pyrolysis kinetics of scrap tire rubbers tested in this study were investigated to formulate the functional relationships of pyrolysis temperature and heating rate. The pyrolysis time decreases exponentially with increasing pyrolysis temperature and heating rate, indicating high activation energies of pyrolysis reaction of the scrap tire rubbers tested in this study. The effect of heat transfer on the pyrolysis kinetics was evaluated by seeking the functional relationship between the sample size and pyrolysis time. The pyrolysis time increases linearly with increasing sample diameter. The slope of the straight line is proportional to the specific heat of the sample.