A method for managing a carcass structure building line, a plant and a process for building tyre carcass structures, wherein the plant includes a carcass structure building line provided with a plurality of stations including an unloading station and n building stations. A group of forming drums being processed includes m forming drums being processed defining a first size of carcass structure being processed. Three groups of entering forming drums include respective entering forming drums, defining a second size of carcass structure being processed. A pair of support elements being processed includes a first and a second support element being processed and three pairs of entering support elements respectively include a first and a second entering support element. The invention also relates to a method for managing a carcass structure building line.