Relationship of Tire Rolling Resistance to the Viscoelastic Properties of the Tread Rubber

For radial and belted bias automobile tires having replicate bodies but different tread materials, the rolling resistance force was found to be nearly a linear function of the tread material loss ratio (fractional hysteresis) measured at either constant strain or constant stress. Loss ratio is calculated as the ratio of energy loss (hysteresis) to total energy input obtained from constant crosshead speed (sawtooth) loading cycles on an Instron tester. Good correlation was also observed between rolling resistance force and a viscoelastic index (loss tangent) obtained from sinusoidal strain cycles on a Rheovibron instrument. When related to energy loss of the tread, rolling resistance showed good correlation only for a series of natural rubber compounds of varied black content; a tread based on a solution styrene-butadiene rubber polymer fell outside the natural rubber pattern.