Rubber composition containing carbon black

A rubber composition comprising:

• (i) a carbon black-containing rubber composition obtained by coagulating, dehydrating, and drying a rubber latex mixture containing 50 to 90 parts by weight, in terms of solid components, of latex of at least one starting rubber A having an average glass transition temperature TgA of -120.degree. C. to -15.degree. C., 40 to 100 parts by weight of carbon black, and 70 parts by weight or less of a softening agent, and
• (ii) a starting rubber B having an average glass transition temperature TgB in the relationship of TgA+10 (.degree.C.).ltoreq.TgB, said starting rubbers A and B being present in the rubber composition in an amount such that the total amount of the starting rubbers A and B is 100 parts by weight, and optionally a softening agent in an amount such that the total amount of softening agent in the rubber composition is 80 parts by weight or less,
• the carbon black-containing rubber composition (i) being mixed with the starting rubber B (ii) in an internal mixer, and at a ratio F.sub.A /F.sub.B of from 1.2 to 3.0, wherein F.sub.A is a concentration of the carbon black in the starting rubber A and F.sub.B is a concentration of the carbon black in the total amount or rubbers A and B.