Abstract: A tool for checking the alignment of bicycle frames includes threaded sleeves for threading into the bottom bracket shell of the bicycle frame, and a gauge bar adapted to be held in contact with the sleeve. The sleeve and the gauge bar have precisely machined engagement surfaces so that when assembled and clamped together, for example by a vise, the gauge bar is held precisely perpendicular to the central movement, i.e., bottom bracket, of the bicycle frame, with the gauge bar positioned to extend along the down tube or seat tube of the bicycle frame so that any deviations thereof from perpendicularity with the central movement can be measured.