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Broken spoke crack surface detail This spoke, a Sapim Laser (1.7mm diameter at the elbow), mounted as an "inbound" spoke on the non-drive side of a rear wheel, broke at the elbow. The crack appears to have started on the inside of the elbow. The crack propagated to the left, normal to the banding seen in the crack surface. The spoke failed when only about 1/6 of the original material remained attached, leaving a 45-degree shear failure that can be seen at the left.