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In the commercial production of styrene-butadiene copolymers, the finished product is dried by oven-type dryers or by mechanical-type dryers. Our goal was to determine if, and to what extent, the severe conditions of mechanical drying effect the viscoelastic properties of the copolymer. It was determined that mechanical drying added to the “shear history” of the polymer and contributed to premature breakdown. Furthermore, the rheological properties of the polymer are altered in a manner that suggests the presence of long-chain branching. These alterations persist in the compounded stock as variations in the elastic properties of the uncured material. The shear history of a compound is important to its processibility. This history begins at the production of the base polymers and may be of concern to the user.