This study describes the effect of treatment of Bis(3-triethoxysilyl propyl)tetrasulfane (silane coupling agent, Si69, TESPT) on in situ sodium activated, organo modified bentonite clay - styrene butadiene rubber (SBR) nanocomposite. transmission electron microscopy and Wide angle X-ray diffraction indicated the intercalation as well as partial exfoliation in both the organoclay and silane treated organoclay compound. It was found that about 5% of silane with respect to clay was the optimum dose for the treatment. Around 15% improvement in tensile and tear strength was observed due to silane treatment. Silane treated organoclay exhibited substantial improvement of the fatigue life, compression set, and rebound property. A detailed study of physical property was carried out. A comparison with low and high structure carbon black filled compound was also carried out. It revealed that the silane treatment helped organoclay to achieve comparable property of the compound having equivalent carbon black loading. Probable mechanism of interaction of silane with clay has also been proposed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116:1660-1670, 2010