Methods are described for treatment of aramid fibers to modify the surface of the fibers. The treated fibers have improved adhesion to elastomer materials as compared to untreated fibers. Modification methods include irradiating the fibers, compressing and straining the fibers under a constant pull force and immersing the fibers in a coupling agent fluid. The treated fibers can be used with elastomers and provide reinforcement elements in products such as tires.