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.
The very first Paramounts seemed to have had serial numbers starting with “A” followed by two or three digits. This seems to have been a system started by Emil Wastyn. We found a very early Paramount – claimed to be a 1938-9 vintage – with serial number A545. Little is known about serial numbers for bikes built after World War II. Some Japanese bikes may have an 'X' in the month position of the frame serial number. This was used to keep the physical year of production, for example 'X9' - December of 1979, with the model year of the remainder of the production for that model - 1980. 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. Kids Fat Bikes Find Your Ride. BMX Mountain Urban Kids Scooters Electric News May 07, 2021. Follow Mongoose @MONGOOSEBIKES @MONGOOSESCOOTERS.
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.
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.
Mongoose Bike Serial Decoder Free
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 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
Mongoose Mountain Bike Serial Numbers
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 the GT BMX you have, visit our BMX Catalogue website. You'll find all the original catalogue info you need including original parts lists, specs, colours and photos of restored bikes.
There is no function for me to reply to comments left on this post.If you have a BMX and don't know what the serial number means. I might be able to help. Go to our Facebook page https://www.facebook.com/rerides.bmx and give us a like! Then upload a photo of your bike and the serial number. We'll take a look and try to help you out.
Thanks for reading. If you liked this post, sign up to the blog via email at the bottom of the page and get every post direct to your inbox. For more information on this BMX and more, you canLIKE my Facebook page, to receive regular updates in your feed, visit there-rides websiteor see the rebuilt and restored rides and parts for sale on our eBay store. For more images of all our re-rides in progress follow us on Instagram.
Info On Mongoose:
http://www.vintagemongoose.com/
MONGOOSE MOTOMAG: 1975 - 1983
1st gen. gusset by the bottom bracket, a coaster tab but no brake bridge. (Sept'75-Jan'77)
Serial Numbers
(located on the underside of hanger cup/bottom bracket shell):
1975 serial numbers were a hand-stamped five number, individual frame ID. They begin at 10001 and continue until early 1976 when a revised stamp begins to include place of manufacture indicated with the letter 'C' ( for Chatsworth, California) followed by the five number individual frame ID. It then changes again later into 1976 to include place of manufacture/month/year code followed by a five number individual frame ID. Example: CB6 ##### (C=Chatsworth B=February 6=1976). After February 1977, (CB7) the second generation frames appear without the extra gusset between down tube and seat post tube.
2nd gen. removed BB gusset and added brake bridge. (Feb'77-June'79)
3rd gen. removed coaster tab. (July'79-June'81)
4th gen. step down, 2-hole dropouts were added. July '81
SER # Breakdown
For the first year or so it was a hand stamped 4 or 5-digit #. '75 -'76
13054C
17407
The most common # was from '76 - Feb.'81
CA7CL9
31909255406
From '81-'83 they started using this code (it moved around alot)
H159989A3002876
TEAM MONGOOSE 1978 - 1980
There are some Team frames from late '77
full production started in 1978.
they came in Candy Red or Blue over Nickel. 100% Chromoly.
T
CG9
191147
Submitted by Mongoose (View all 77 posts)