Process for building tyres for vehicle wheels

A method for building tyres for vehicle wheels, wherein at least one elastomeric component of a tyre is made by applying at least one continuous elongated element according to a plurality of turns (C) around a forming drum rotating around a geometric rotation axis thereof;

• wherein a method of making the continuous elongated element comprises:
• extruding a first material, when a supply of the first material is activated, through an extrusion nozzle, to form an inner core of the continuous elongated element exiting from an outlet opening of the extrusion nozzle;
• and
• during the extrusion, activating a supply of a second material different from the first material, for conveying the second material around the first material, at the extrusion nozzle and upstream of the outlet opening, to form a coating layer, wherein the coating layer surrounds the inner core;
• wherein the second material is introduced into a second supply duct leading to an injection chamber arranged around a first supply duct axially converging into an outlet channel, the outlet channel longitudinally crossing the extrusion nozzle and leading to the outlet opening, the injection chamber flowing into the outlet channel through a radial intake slit extending along a closed line around the outlet channel, and
• wherein the radial intake slit has a variable axial dimension along a peripheral development thereof.