Rubber composition manufacturing method and tire manufacturing method

A rubber composition manufacturing method comprising an operation in which an intermeshing internal kneader equipped with a casing, at least two rotors which are capable of rotating within the casing, a neck portion which is located above the rotors, and a ram which is capable of moving vertically in a space within the neck portion is used to knead at least rubber, silica, and silane coupling agent, wherein

• the operation comprises a first step in which kneading which is accompanied by increase in kneading temperature is carried out during an initial phase of the operation;
• the operation comprises a second step in which, after the first step, kneading is carried out while the kneading temperature is controlled so as to suppress occurrence of a coupling reaction between the silica and the silane coupling agent, rotational speeds of the rotors being controlled by means of PID control to cause the kneading temperature to be a target temperature at the second step;
• the target temperature is not less than 100° C. but less than 140° C.,
• kneading is carried out during the first step while the ram is maintained in a state in which it is at a first position which is higher than a lowermost position within a range of movement of which the ram is capable;
• and
• a volume of space which is enclosed by the ram and the casing when the ram is at the lowermost position to be a first effective volume, and a volume of space which is enclosed by the ram and the casing when the ram is at the first position to be a second effective volume, the second effective volume is 105% to 120% relative to a value of 100% for the first effective volume during the first step.