In addition to the traditional reinforcing filler, carbon black, silica has increasingly been used in tire tread compounds. This is because silica can significantly reduce the rolling resistance of tires, improving fuel efficiency.1 Because of the hydrophilic nature of silica, a silane coupling agent is added to the silica formulations to achieve adequate filler dispersion and strong chemical bonds between the silica and a hydrophobic or non-polar rubber.2 Due to the demand from tire producers for further improvements in compound performance – to meet OE tire requirements – silica manufacturers have developed a new type of silica, referred to as highly dispersible silica, with two key characteristics: specific surface area and structure, determined by cetyltrimethylammonium bromide (CTAB) absorption and by the oil absorption number (OAN). The CTAB value measures the specific surface area of silica that is accessible to the polymer chains. For the OAN measurement, di-(2-ethylhexyl) adipate (DOA) is used to fill the void volume of silica (the space between the solid particles) and refers to the structure of the silica. Thesecrucial properties of silica highly influence the performance of rubber compounds and vulcanizates.3 Moreover, two types of silica have been developed for better material handling purposes during mixing and storage, referred to as granulate and micro-pearl forms. In general, silicas are divided into two groups: conventional silica (CV) and highly dispersible silica (HD). The main differences between these categories are their structures. The three-dimensional clusters of HD silicas have greater void volume (referred to as high structures) compared with CVs.3,4,5 It has been reported that the macro-dispersion of silica and filler rubber interaction in rubber compounds can be improved by this high-void volume. This was explained by the higher possibility for rubber molecules to penetrate into the voids of the silica clusters, resulting in higher rubber filler interactions.4,5 Therefore, it is worth paying attention to elucidating how the raw forms (granulate and micropearl), structure and specific surface area of silicas influence the overall performance of rubber tread compounds. In this study, various commercially available silica grades were investigated. Different forms of silicas along with varying DOA and CTAB values were chosen to address thesequestions. Their influence on the dynamic and mechanical properties of the compounds were evaluated.