Kristinn, At what pitch a string will break is a function of hit's speaking length. A top C note of 51 mm speaking length, 13 gauge wire, 156 pounds tension and has a breaking per cent tension of 64%. Change the speaking length to 53 mm, 13 gauge, 168 pounds and 70% breaking tension. 70% is outside acceptable range because any additional friction and a bit of age and the string will break. It does not matter what size string you install it will break at the same pitch, approximately. 49 to 51 mm speaking length is the acceptable range for a piano. In order to determine at which tension such a string will break I would have to put on my thinking cap and math hat and right now I am too tired for such arduous work. Newton
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