In the multi wire sawing process the wire tension is an important parameter for reliability and wafer quality. Changes of wire quality and wire tension from one end of a wire web in a multi wire saw to the other are investigated by several methods: wire tension measurements in the wire saw, wire elongation during an industrial process and material testing of representative wires. Two mechanisms for the loss of wire tension are identified. Firstly, the decrease of wire diameter due to abrasion causes a slow loss of wire tension along the whole wire web. Secondly, plastic deformation of the wire due to random overloading leads to a fast decrease of the wire tension within the first few centimeters of the wire web. Both effects are confirmed by modeling and calculations. (C) 2013 Elsevier B.V. All rights reserved.