The usual format is 2-3 letters and 6-8 numbers (e.g. XX1234567), but may be also only numbers (usually at least 6 numbers). Newer bikes often have a sticker with this number on more convenient place (e.g. on frame above pedals axis).
Can’t find it
If you cannot find it, there is a big chance you will succeed on the bottom of the bike, where it’s usually hidden below dirt (have a wet wipe at hand).
Some bikes do not have any frame number at all ever since the manufacture (this is very rare, though). Some bikes have it visibly removed (scratched) – this is often sign of the bike being stolen in the past.
More numbers?
There may be more ID numbers available – if you are not sure, send us everything you find, we’ll pick the correct one.
Picture source: http://www.stopfietsdiefstal.nu/
