How to read GT serial numbers for mid-school and new-school BMX bikes

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The first thing everyone wants to know when the buy a second hand GT BMX is ‘how old is it?’ Reading the GT serial number and finding out the build date is an important part of any BMX restoration. Once you now when the old GT BMX bike was built it’s much easier to find out what model it is and also look at the original parts lists and colours from the bike makers catalogues.

A while back I spend some time investigating how to read mid-school and new school serial numbers on Mongoose BMX bikes.

After buying and restoring a number of older mid-school and new school GT BMX bikes I also need to to figure out how to crack the GT serial numbers to get the same build date information.

GT BMX serial numbers 1

It didn’t take long to realise there were many similarities when looking at GT serial numbers and Mongoose serial numbers. The placement and sequence of the numbers is stamped in the same place under the bottom bracket. Many of the GT serial numbers start with the same letter sequence. After a bit of digging around online I soon realised that GT BMX bikes and Mongoose BMX bikes were owned by the same company and also made in the same factories in Taiwan. In fact look closely at many Mongoose and GT BMX’s from the around 2000 to 2010 and you’ll see many similarities in frame design and geometry. This is probably not true for all of the bikes in either range, but there were a number of bikes that were identical apart from the logo stamping. Anyway that’s a post for another time.

As with the Mongoose serial numbers there are many posts from forum members around the world on old-school GT serial numbers, but very little on mid-school or new school.

Of course there are also many variations in GT serial numbers and I have focussed mainly on cracking the new-school numbers for now. That is bikes made between 2000 and 2010, and those bikes made in the Taiwan factories with specific serial number sequences. There will be bikes that are different, if you have any examples of where this crack doesn’t work, add a comment below.

GT BMX serial numbers 2

GT serial numbers are usually found stamped on the bottom of the bottom bracket of your BMX. This is not always the case and there will be some bikes that do not fit into this formula.

For mid-school GT BMX bikes built in Taiwan through most of the 90’s with a serial number that begins with 4 letters before the series of numbers. The 3rd letter corresponds to the year of manufacture.

1991-2000 – 4 letters at beginning, 3rd is year

A    B    C    D     E     F    G    H     I      J
91  92   93   94   95   96   97   98   99   00

The 4th letter indicates the Month

A      B      C      D      E      F     G     H     I         J       K      L
Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sept   Oct   Nov  Dec

A few examples are:

HFGB00000 – 4 letters, GB are the dates. G is the year (1997), B is the month (Feb)

HFBH00000 – 4 letters, BH are the dates. B is the year (1992), H is the month (Aug)

For new-school GT BMX bikes built through most of the 2000’s with a serial number that begins with 5 letters. The 4th letter corresponds to the year of manufacture and follows on from the mid-school serial numbers.

2001-2010 – 5 letters at beginning, 4th is year

K    L     M    N    O   P    Q    R   S    T
01  02   03   04   05  06  07  08  09  10

The 5th letter indicates the Month

A      B      C      D      E      F     G     H     I         J       K      L
Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sept   Oct   Nov  Dec

A few examples are:

HAMRF00000 – 5 letters, RF are the dates. R is the year (2008), F is the month (Jun)

HAMOI00000 – 5 letters, OI are the dates. O is the year (2005), I is the month (Sept)

Please note: The GT serial number will give you the build date of your GT BMX. Frames were normally manufactured the year before being sold in bike shops. So a build date on a frame of 2003 usually means the bike was sold in stores in 2004.

If you want to know more about your GT BMX visit BMX Catalogue - you'll find all the original catalogue info you need including original parts lists, specs, colours and high resolution photos perfect for rebuild reference.

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BMX Restoration GT GT BMX GT Serial Number serial numbers

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