Recent developments, mainly from the automotive industry, require the use of rubbers with improved chemical and thermal stability. To meet these demands, rubber producers have developed new polymers or have modified existing ones. The result has been that less reactive polymers are employed which as a consequence exhibit increased difficulty in adhering to reinforcing yarns and cords. This paper presents the results of some experiments carried out to obtain acceptable adhesion levels of aramid and polyester reinforcing cord to EPDM and HNBR rubber in the mechanical rubber goods application field. It has been demonstrated that modifications in the RFL latex component in combination with slight alterations in the rubber formulation results in sufficient adhesion of both aramid and polyester cord to EPDM and HNBR rubber.