Method for calibrating optical tools of a tyre checking system, said method comprising: providing a calibration apparatus, comprising a first engagement portion and a second engagement portion; providing a plurality of optical tools, each optical tool being adapted to be mounted on a mounting portion of an automated structure of said tyre checking system; associating each one of said optical tools, in sequence, with said first engagement portion, said first engagement portion comprising a replica of said mounting portion; associating a reference element with said second engagement portion; the method being characterized in that, for each optical tool associated with said first engagement portion, the following operations are carried out: associating to said optical tool a visible representation of an optical axis of said optical tool, said visible representation being a tangible representation of said optical axis, said visible representation comprising a shaped rod equipped with a pointed portion, the longitudinal extension of the pointed portion defining the optical axis of the optical tool; adjusting the mutual position of the optical tool and of said reference element, said adjusting the mutual position of the optical tool and of said reference element comprising placing the pointed portion in contact with reference element, in a predetermined position; after the pointed portion is placed in contact with the reference element, detecting, through the optical tool mounted to said first engagement portion, one or more images showing at least a part of said reference element; performing a calibration of the optical tool based on said detected images. providing a calibration apparatus, comprising a first engagement portion and a second engagement portion; providing a plurality of optical tools, each optical tool being adapted to be mounted on a mounting portion of an automated structure of said tyre checking system; associating each one of said optical tools, in sequence, with said first engagement portion, said first engagement portion comprising a replica of said mounting portion; associating a reference element with said second engagement portion; the method being characterized in that, for each optical tool associated with said first engagement portion, the following operations are carried out: associating to said optical tool a visible representation of an optical axis of said optical tool, said visible representation being a tangible representation of said optical axis, said visible representation comprising a shaped rod equipped with a pointed portion, the longitudinal extension of the pointed portion defining the optical axis of the optical tool; adjusting the mutual position of the optical tool and of said reference element, said adjusting the mutual position of the optical tool and of said reference element comprising placing the pointed portion in contact with reference element, in a predetermined position; after the pointed portion is placed in contact with the reference element, detecting, through the optical tool mounted to said first engagement portion, one or more images showing at least a part of said reference element; performing a calibration of the optical tool based on said detected images. associating to said optical tool a visible representation of an optical axis of said optical tool, said visible representation being a tangible representation of said optical axis, said visible representation comprising a shaped rod equipped with a pointed portion, the longitudinal extension of the pointed portion defining the optical axis of the optical tool; adjusting the mutual position of the optical tool and of said reference element, said adjusting the mutual position of the optical tool and of said reference element comprising placing the pointed portion in contact with reference element, in a predetermined position; after the pointed portion is placed in contact with the reference element, detecting, through the optical tool mounted to said first engagement portion, one or more images showing at least a part of said reference element; performing a calibration of the optical tool based on said detected images.