I have an incomplete diamondback outlook I'm trying to put back together. I don't know the year it was made for looking up specs so I'm trying to look at serial number. However there's a number on the underneath of the BB and on the tube next to it. Which one is it? How do I decode it. The one on BB is YF99G06415. Does that mean it's from 1999?

  • Try digging through oldschoolbmx.uk/diamond-back-bmx-frame-identifier if you're positive its a diamondback. Some sellers put fake decals on, makes it hard.
    – Criggie
    Commented Sep 2, 2022 at 23:30
  • Ok I'm going to try that now. Thanks! Will let you know how it goes
    – Alison
    Commented Sep 4, 2022 at 4:45

1 Answer 1


On Diamondback bikes, the serial number is located on the underside of the frame where the pedals and crank arms attach (in other words, the underside of the bottom bracket shell). Look for a string of letters and numbers. The serial number is usually formatted like U161K0123456 or DAY16A123456.

This is quoted from another forum where they are discussing Diamondback bikes and their history: "The first 2 or 3 characters are usually letters. This identifies the frame factory (the frame factory is not usually the same as the brand). In many cases a Diamondback frame will show either ACs (Accell, the current owner of the brand) or K* (Kinesis, another big bicycle frame builder). There are other variations for other brands (Schwinn and GT frames usually start with SN). The next 2 to 4 numbers tend to be the date of manufacture. 0911 would generally mean November 2009, but then again, there are variations. The final 4 numbers is usually the production sequence... where that particular frame falls in the entire day production which may include several different types of frames."

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