Most bicycles have the serial number stamped onto the bottom bracket where the pedals rotate. Other areas include the underside and the bottom of the seat bar. Some companies locate serial numbers near the seat. Locations include the top or underside of the frame's top bar or at the opening where the seat stem is inserted.
Various Schwinn models stamp serial numbers at several locations. Areas include the head tube, which connects the handle bars with the front-wheel fork, and the rear dropout, which holds the rear tire. Schwinn's older models have numbers stamped onto both sides of the rear dropout; the number on the non-drive side is the serial number.Learn more about Bicycles