How to recognize a stolen bike before buying

Why this matters

In France, 400,000 bikes are reported stolen every year. A significant portion is resold on used platforms. If you buy a stolen bike, even in good faith, you can be forced to return it without reimbursement. Better to check first.

The serial number: where to find it

Every bike has a unique serial number stamped by the manufacturer. It's most commonly found:

• Under the bottom bracket (the most common spot — flip the bike)
• On the seat tube (inner side, near the junction)
• On the right rear dropout
• On the top tube (sometimes under a sticker)

The number typically has 6 to 15 characters (letters and numbers). If the number is missing, filed off, or covered, it's a major red flag.

Databases to check

BICYCODE (France)

The national bike marking system. Since 2021, marking is mandatory for every new bike sold by a professional in France.

• Website: bicycode.org
• Checks: if the number is registered as stolen
• Limitation: only covers marked bikes (not older ones)

Bike Index (international)

International stolen bike database, widely used in the US and Europe.

• Website: bikeindex.org
• Checks: serial number + brand/model
• Free and open

Police database

In France, you can also call the local police station to check if a serial number is reported stolen.

The 8 red flags

1. Serial number missing or filed off — The most obvious sign. No legitimate reason to remove a serial number.

1. No receipt or proof of purchase — A legitimate seller has an invoice, order confirmation, or at least an email.

1. Abnormally low price — A Canyon Aeroad carbon at €500? A Trek Madone at €800? Too good to be true.

1. Brand stickers removed — If the frame decals have been removed or covered, someone is trying to hide the bike's identity.

1. Seller refuses test ride — An honest seller lets you ride the bike. A rushed seller wanting cash immediately is suspicious.

1. Cut marks on the frame — Angle grinder or bolt cutter marks near the seat tube or frame indicate a cut lock.

1. Cut lock sold with the bike — Some sellers "forget" to remove the broken lock. It's an admission.

1. Seller doesn't know the bike — If the "owner" can't tell you the size, groupset, or year, it's suspicious.

What to do if you suspect a stolen bike?

• Don't buy it. Even if it's a good deal, you risk losing it.
• Note the information: serial number, photos, listing description, seller profile
• Report it on the platform's website
• Contact police if you have a serious doubt

Marking: protect your own bike

Since 2021, BICYCODE marking is mandatory for every new bike sold by a professional in France. But you can also get a used bike marked:

• Cost: €5-15 at an approved bike shop
• Process: laser or chemical engraving on the frame + database registration
• Benefit: if stolen, police can trace the owner

Have doubts about a bike you want to buy? L'Atelier helps you identify the model, check specs and spot inconsistencies (wrong groupset for the year, incompatible components).