Steel cord for rubber reinforcement

A steel cord, said steel cord comprising a first group of core filaments having a number of m and a second group of sheath filaments having a number of n, the sheath filaments of said second group and the core filaments of said first group being twisted with each other,

• wherein said core filaments being not twisted with each other, the core filaments being parallel or having a twist pitch being more than 300 mm, said sheath filaments having a twist pitch being less than or equal to 30 mm,
• wherein Dc is substantially equal to Ds, Dc being an average diameter of the core filaments, and Ds being an average diameter of the sheath filaments, Dc and Ds are in the range of 0.10 mm to 0.40 mm, and
• wherein said core filaments have an average tensile strength Tc in MPa when being un-ravelled from said steel cord, said sheath filaments have an average tensile strength Ts in MPa when being un-ravelled from said steel cord, 4100−2000×Dc<Tc<4300−2000×Dc, 4100−2000×Ds<Ts<4300−2000×Ds, said Dc and said Ds being expressed in mm, said Tc and said Ts satisfying:
• 5<(Tc−Ts)<200.