A stainless steel wire for reinforcing the crown (1) of tires (100), comping at least 0.02% and at most 0.2% carbon, at least 6% and at most 10% nickel, at least 16% and at most 20% chromium, the content of molybdenum of the steel being zero or at most equal to 5%, the total of the nickel, chromium and molybdenum being at least 23% and at most 28.5%, all these percentages being % by weight; the structure of the steel comprises at least 50% by volume martensite and it is without austenite or comprises less than 50% by volume thereof. Assemblies (620), reinforcement plies (62) and tires (100) comprising this wire. Process for preparing this wire.