Device for manufacturing a cut-to-length pre-assembly for a tire, wherein in the pre-assembly first and second side walls are situated on either side of an inner liner. The device comprises a supply conveyor for conveying the cut pre-assembly to the building drum. The device is provided with a first side wall measuring device for measuring the length of the first side wall of the cut pre-assembly and for giving a first side wall measuring signal indicative of the measured length of the first side wall, with a second side wall measuring device for measuring the length of the second side wall of the cut pre-assembly and for giving a second side wall measuring signal indicative of the measured length of the second side wall, and with an inner liner measuring device for measuring the length of the inner liner of the cut pre-assembly and for giving an inner liner measuring signal indicative of the measured length of the inner liner.