The use of aramid fibers as a reinforcing material in both tires and mechanical rubber goods, such as hoses, belts, etc., is growing. In these dynamic applications, the adhesion between fiber and rubber is critical. This can be optimized by activating the aramid with an epoxy formulation, followed by RFL (Resorcinol Formaldehyde Latex) treatment. In the past, various combinations of analytical techniques have been used to study the relationship between the fiber surface treatment, the resulting microscopic interphase structure and the macroscopic rubber properties. The fundamental knowledge acquired from these past studies has been exploited here to investigate the effect of oily finish components on the aramid-rubber adhesion. For this purpose, aramid yarn has been treated with various combinations of an adhesion improving (epoxy-amine) component and a processability improving (oily) component. Contrary to general belief, the oily components do not directly reduce the SPAF (Strap Peel Adhesion Force) to rubber, rather show some positive effect. Furthermore, there is a relative broad 'safe' oil range, i.e., fluctuations in the amount of oil will not directly lead to adhesion problems. This is in line with earlier observations, but this study using appropriate analytical techniques provides quantitative confirmation and additional understanding of the fundamental principles behind these effects. (C) Koninklijke Brill NV, Leiden, 2009