Process and apparatus for manufacturing tyres for vehicle wheels

A carcass ply is built on a forming drum by application of a plurality of strip-like elements by the steps of: setting a width of these strip-like elements, setting a width of the overlapped part between two adjacent strip-like elements, setting a fitting diameter of the forming drum by calculating a corresponding extension of a radially external laying surface, and calculating a whole number of strip-like elements to be applied. The whole number of drip-like elements is applied by rotating the forming drum around a geometric rotation axis thereof, and applying pairs of strip-like elements by means of a first laying unit and a second laying unit located close to opposite portions of the forming drum relative to the geometric rotation axis. When the calculated whole number of strip-like elements is an odd number, before at least one application step, the first laying unit is shifted along an adjustment path orthogonal to the geometric rotation axis and substantially tangent to the radially external laying surface of the forming drum.