A process and a tyre manufacturing line for producing tyres, wherein the process includes the steps of: i) transferring a first toroidal support to a first assembling apparatus; ii) in the first assembling apparatus, sequentially building on the first toroidal support a first toroidal carcass ply and a first pair of annular reinforcing inserts so as to associate each annular reinforcing insert with a respective radially internal edge of the first toroidal carcass ply; iii) transferring the first toroidal support to a second assembling apparatus; iv) in the second assembling apparatus, sequentially building on the first toroidal support, carrying the first toroidal carcass ply associated with the first pair of annular reinforcing inserts, a second toroidal carcass ply and a second pair of annular reinforcing inserts so as to associate each annular reinforcing insert with a respective radially internal edge of the second toroidal carcass ply.