Silica is widely used in passenger tire treads to improve the balance between wet traction and rolling resistance, compared to the balance achieved when the filler is strictly carbon black. Improvement in wet traction with silica is attributed to the difference in energy loss encountered at high frequencies. The energy loss difference is deduced from the difference in shift factors, determined by time temperature superposition in viscoelastic testing of silica compounds compared to carbon black compounds. Further investigation indicated that some mineral fillers other than silica showed similar behavior. Thus, some mineral fillers could improve tire wet traction without adverse effects on other tire performance traits.