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How To Find Your Bike's Serial Number

You need to know your bike's serial number if you want to register it with Bike Index or sell it to The Pro's Closet. Here's how to find and identify it.

Written by: Bruce Lin

Published on:

Posted in:Guides

There is one important number that every cyclist should know. No, not your bike’s frame size, geometry, or weight. We’re talking about your bike’s serial number. 

It's a good idea to keep your bike’s serial number copied somewhere safe, just in case you need it. Better yet, we recommend registering your bike’s serial number with Bike Index, the world’s largest bike serial number database. This keeps your serial number stored online where you can easily reference it, and if your bike is ever stolen, it will increase your chances of recovering it

If you plan to sell your bike to TPC, you will need to provide your serial number to complete the sale. If you’ve purchased a bike from TPC, you’re in luck! All bikes sold by TPC are automatically registered on Bike Index. You will receive an email shortly after purchase asking to confirm your bike’s registration. 

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Where Is Your Bike’s Serial Number?

  • Serial numbers are a combination of letters and numbers most often found on the underside of your bike’s bottom bracket (the part of the frame where the crank arms attach).

It may be engraved, printed, or on a sticker. Serial numbers may be accompanied by a barcode, QR code, or preceded by the abbreviation “s/n.” To view the serial number you will need to place the bike in a repair stand or flip it upside down. 

If you can’t locate the serial number on the underside of your bottom bracket, there are a few other possible locations:

  • The underside of the top tube or down tube - This is common with Specialized and Giant bikes, which have additional serial number stickers applied here. 
  • Rear dropout or head tube - Some vintage and custom-built steel and titanium frames have serial numbers engraved at the rear dropouts or head tube. 
  • Proof of purchase - If you purchased your bike from an authorized dealer, the proof of purchase will often contain the serial number. 

If you can’t locate your serial number, the best course of action is to contact your bike’s manufacturer for help. Some custom and handbuilt bike frames won’t have serial numbers because small builders don't track them. 

What Is NOT a Serial Number?

Where to find your bike serial number, what's not a serial numberBikes often have numbers on the frame that can be easily mistaken for serial numbers. Here are some common numbers that are NOT serial numbers: 

  • ISO numbers - These are an international standard for labeling and outlining industry safety standards that the frame is in compliance with. You can learn more about the meaning behind ISO numbers here.
  • EN numbers - European Standards (EN) are documents that have been ratified by one of the 3 European Standards Organizations, CEN, CENELEC, or ETSI. These are not serial numbers and are not unique to individual bikes.
  • Rear triangle serial numbers - Many full-suspension mountain bikes will have serial numbers on the rear triangle. These serial numbers often do not match the true serial number, which will be located on the front triangle. 


Common Bike Serial Number Locations and Formats: Specialized, Trek, Giant, Cannondale & More.

To help you recognize your bike’s serial number, here are some examples of common serial number locations and formats used by major brands. 





Sticker under bottom bracket or top tube. Starts with WSBC. Older models can start with STU or WUD. 

WSBC602033449H, WUD094016606E


Under bottom bracket or top tube. Begins with WTU or WL in the form WTU###x###x or WL#######

WTU171G0193G, WL3420591


Sticker with a barcode under the bottom bracket or frame. xx##### format.

MM32185, YB73660


Under the bottom bracket, head tube, or battery in the format xx####### or xx##x#####. 

GQ1701946, E4CA2965

Santa Cruz

Etched into the frame above and behind the bottom bracket, on a QR sticker, or stamped into the frame. “PS #### P-# #### Size” format is common for newer models. 

PS 1712 P-1 0681 M CC, A40855111, GFSNL0013GL01735


Under bottom bracket, often with barcode

01190148070, SNAFT18G02491, XNM1794


Under the bottom bracket. For late models, the 4th and 5th digits indicate the production year.

21518G30038, AC15800176


Stickers under BB. There is sometimes a matching sticker by the rear brake. The 1st digit usually indicates the production year. 

8H5FD310070, 0IFFD410051

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Hopefully, this makes finding your bike's serial number a bit easier. If you have any questions, our expert Ride Guides are available to help you seven days a week from 9AM-6PM MT and can be reached via online chat, phone: 866-401-9636, or email: during those hours.

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