Modified thermoplastic hydrocarbon thermoplastic resins are provided, as well as methods of their manufacture and uses thereof in rubber compositions. The modified thermoplastic resins are modified by decreasing the relative quantity of the dimer, trimer, tetramer, and pentamer oligomers as compared to the corresponding unmodified thermoplastic resin polymers, resulting in a product that exhibits a greater shift in the glass transition temperature of the elastomer(s) used in tire formulations. This translates to better viscoelastic predictors of tire tread performance, such as wet grip and rolling resistance. The modified thermoplastic resins impart remarkable properties on various rubber compositions, such as tires, belts, hoses, brakes, and the like. Automobile tires incorporating the modified thermoplastic resins are shown to possess excellent results in balancing the properties of rolling resistance, tire wear, snow performance, and wet braking performance.