Where can I find the serial number of my bike? Posted on February 15, 2018 by Niels Each Lekker Bicycle features a unique serial number that identifies the make and the model of the bike. You’ll find the serial number just underneath the bottom bracket of the bike where the crank arms meet the frame. Niels Where can I register my bike to assist in the event of theft? What can I do if something happens with my bike after my warranty has expired?