What Is a Frame Number?
Every bicycle has a unique serial number stamped into the frame during manufacturing. It's the bike equivalent of a car's VIN. No two bikes should have the same number.
This number is your best tool for:
- Verifying a bike isn't stolen before you buy it
- Proving ownership if your bike is stolen
- Insurance claims, most insurers require it
- Registration on theft databases like BikeRegister
Where to Find It
The location varies by manufacturer, but the most common spots are:
Bottom bracket shell (most common): Flip the bike upside down and look at the underside where the pedal cranks attach. You may need to clean off grime.
Head tube: The tube at the front where the fork goes through. Check the front, back, and underside.
Rear dropout: Where the rear wheel axle attaches to the frame. Less common on modern bikes.
Seat tube: Occasionally stamped low on the seat tube, near the bottom bracket.
The number is typically 6-12 characters, often a mix of letters and numbers. Some brands (Trek, Specialized) use longer codes that encode the model and year.
How to Check If a Bike Is Stolen
BikeRegister
The UK's national cycle database, used by all UK police forces. Search at bikeregister.com/bike-checker. It's free to check.
CheckThatBike
Another free tool that cross-references multiple databases.
Local police
You can ask your local police to run a serial number check. Some forces have online tools; others require a phone call.
Cyclesite
When you list a bike on Cyclesite, we automatically check the frame number against stolen bike databases. This protects both buyers and sellers.
What If the Frame Number Is Missing?
Some legitimate reasons a frame number might be hard to find:
- Paint over it, some resprays cover the serial number. Not ideal, but not necessarily sinister.