Do this the day you bring the bike home. A serial number you've already written down is worth far more than one you're hunting for after a theft.
Why police ask for it
The University of Southern California's public safety department puts it simply. The best chance at recovering a stolen bicycle is having a registered serial number. These numbers are used by police across the nation1.
The University of Washington Police Department agrees. Knowing your serial number makes it easier to return your bike to you if it's recovered after being lost or stolen2.
So the number does two jobs. It lets police match a bike they find to you, and it's the key most registries ask for.
Registries want it too. Winnipeg's online registry says that to register your bicycle you will require the serial number3. That's a Canadian city service, and registries differ by place.
Where to look
USC says the majority of serial numbers are located under the bottom bracket, where the two pedal cranks meet. Its tip is to turn your bike upside down and record the number1.
If it's not near the cranks, check other common places, including the front headset or rear stays1. The rear stays are the thin tubes that run back to the rear wheel.
Not every maker uses the same spot. Check your owner's manual or the maker's support page for where your model puts it.
What to write down
Keep more than the number. Chicago's city page lists three things. Record the serial number. Keep a photo of you with your unlocked bike. Keep the sales receipt. All of them help you identify the bike if it's stolen4.
For a report, Winnipeg asks you to have the serial number ready. Add any unique marks or engravings that will help match your report to bikes found3.
If there's no number
Some bikes have none, or it wears off. The University of Washington Police Department says to engrave an owner ID on the bike. It adds a warning: never use your social security number2. USC says its department can provide tools to engrave the frame as alternate identification1. Both are US campus services, so ask your own police about local options.
Register it
A written number helps only if someone can match it. Chicago says that if police recover your bike, it's beneficial if you previously registered it with the Chicago Police Department4. University of Washington police point to Bike Index as one place to register2.
Ask your local police which register they use, and read their page for any fee. For more on e-bike theft advice, see why e-bike theft advice differs.
Notes and sources
- Locating your Bicycle Serial Number, University of Southern California Department of Public Safety
- Warning: Thieves want your electronic bikes and scooters, University of Washington Police Department
- Bicycle security, Winnipeg Police Service
- Bike Theft Prevention, City of Chicago
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