A steel cord for rubber reinforcement comprises a first group of m core filaments and a second group of n sheath filaments, where m is 3 or 4. The core filaments form a spiral and the core filaments are not twisted together and are substantially parallel, or the core filaments have a twist pitch greater than 300 mm. The second group and the first group are twisted together, and the sheath filament forms a flat spiral in the same direction of the core filament spiral, the sheath filament has a cord twist pitch, In any cross section, there is at least one gap between two adjacent core filaments. Steel cords have improved frictional resistance and can contribute to a reduction in tire weight.
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