Steel-belted tires are usually made by extruding rubber onto a bank of wires. The resulting steel-polymer composite must meet a gauge specification. However, the composite swells extensively after leaving the die throat, taking on a more or less corrugated appearance. This paper presents an experimental study to understand the influences different parameters have on die swell for this sort of extrusion. Basically, the experiment is conducted to correlate die opening gauge to die swell. Parameters that affect die swell extrudate expansion are identified and investigated. Die opening is varied throughout the experimental process, and the die opening and belt gauge are measured to calculate die swell. To achieve a more uniform gauge across the width of the belt, the die throat opening is divided into five zones. Each zone of each die throat is considered. Experimental parameters held constant include wire parameters, polymer parameters, and setup parameters. The experimental data result in an overall plot of die swell percent vs. die throat opening gauge. This plot can be used as a guideline for predicting required gauge opening in a steel belt gauge development. The study shows that die swell percents for extruded belts is more predictable than previously thought, and debunks the notion that die swell percent is constant. With regard to the time and effort for optimizing future die throat development, some concluding remarks and recommendations are made based on the analysis of the experimental results obtained in this study.