Wood Sawdust as a Low-Cost Filler in Whole-Tire Reclaimed Rubber: Mechanical Characterization and Factory-Scale Cost Analysis

End-of-life tire waste presents a serious disposal problem, and reclaimed rubber (RR) recovered from whole truck tires offers a practical recovery route. However, RR has lower mechanical performance than virgin rubber, and low-cost fillers that maintain acceptable properties are needed. This study examines wood sawdust, obtained free of charge as a carpentry by-product, as a particulate filler in whole-tire RR at 0 to 20 wt%. Composites were manufactured under factory conditions and tested for tensile strength, elongation at break, Shore A hardness, Mooney viscosity, and seven-day water absorption. At 5 wt% sawdust, tensile strength was 4.4 MPa and elongation at break was 148.7%, both within published industrial acceptance limits. Shore A hardness reached 63.5 and Mooney viscosity rose by less than 4%, with no practical processing consequence. Water absorption was 8%, compatible with indoor and semi-exposed applications. All five properties remain within specification at 1 to 5 wt%. A factory-scale cost analysis shows that 5 wt% substitution reduces annual production cost by approximately 62,000 USD with no capital investment required.