Time-temperature superposition principle (TTSP) is widely accepted to be applicable to viscoelastic functions for various polymers and rubbers. In general, we need to determine both horizontal and vertical shift factors (a_T and b_T, respectively) in practical application of TTSP. If elasticity mechanism in viscoelasticity of the aimed sample is known to be entropy elasticity, we may take vertical shifts of viscoelasticity curves at various temperatures by Tρ factors followed by horizontal shifts of curves, as is explained in many textbooks. However, if the mechanism is not known, we must determine a_T and b_T in independent and objective way. The best way is considered to determine a_T firstly by using curves of loss tangent (dimensionless quantity) then b_T by using curves of storage and loss moduli. The application of this method to the experimental data of linear viscoelasticity for SBR gum and filled SBRs showed the next facts: The mixing of various fillers showed no effect on a_T but change in b_T from entropic elasticity in gum to energetic elasticity of enough filled rubber. This may be due to formation of contact filler network at high loading.