To explain, information about Bridgestone serial numbers is information provided by the following sites. First, we would like to shout out a special thanks to Grant Peterson, currently with Rivendell Bicycle Works and to Hummer, senior member of Bikeforums. Additionally, we would like to thank William Bevington and Scott Ryder, authors of the book: Japanese Steel.
The serial number is usually found under the bottom bracket shell. So, if the first
letter is A through G, it was made in January through July.
A = Jan H = Aug
B = Feb I = Sep
C = Mar J = Oct
D = Apr K = Nov
E = May L = Dec
F = Jun
G = Jul
TWO FORMATS
In fact, the serial numbers are normally made up of two formats based on the first two characters:
Thus, Number + Letter
Or, Letter + Number
To point out, the number is considered to be for the year of frame manufacture. In addition, the letter is considered to be for a time period with in the year.
Serial number examples:
E417488 = Therefore, E is the month May /4 the year 1984 /17488 Build no.
H422248 = Therefore, H the month Aug / 4 the year 1994 / 22248 Build no.
Number first Format:
4H11537 = Therefore, the 4 is the year of manufacture. This particular bike had 70’s components. For that reason, the year was determined to be 1974. Next, the H stood for the month or August. / 11537 Build no.
WHAT THE REST OF THE NUMBERS MEAN
Acccording to Mr. Peterson, the rest of the numbers refer to the week and day it was manufactured. However, it is believed that these numbers may include the month as well just because of how many numbers are present.
Moreover, there have been some reported serial numbers starting in various other letters such as, X or M. Until now, there have been no reports to be found as to what these letters indicate.
The serial number on my RB-1 is: H022756. Hence, this would have been manufactured in August of 1990. However, the catalog states that the only colors offered that year were blue, purple and black. On the other hand, my frame is red with a different decal layout.
Notably, in 1991 they did offer a “rich red” color as well as a dark green / tusk color. Although, my frame was manufactured late in the year. So, it may have been released in ’91 with the new color. I purchased the frame and fork only, so I could not use any components to verify my thoughts on this.
Here’s what Hummer, senior member of Bikeforums determined through his investigations.
There are 26 letters in the alphabet.
However, the letters “I” and “O” are not found in my data.
Most of the letters found are in the range A to L (except I) and X.
Alphabet + numbers = Asahi Factory. Asahi factory = sports vehicle
Number + Alphabet = Ageo Factory. Ageo factory = general vehicle
For example, custom Order frames, like Grand Velo. These were custom-made production section in the Ageo factory.
A to L = January to December. However, if the monthly production exceeds 99,999 units, the alphabet will be moved up.
In the list:
A = January
B = February
C = March
D = April
E = May
F = June
G = July
H = August
X = September * The order is <I>, nonetheless, it is easy to be confused with 1. Use <X> as a special case.
J = October
K = November
L = December
Below this, if the monthly production exceeds 99,999 units
MORE LETTERS REPRESENTING THE MONTH
M = January
N = February
Y = March * Although it is <O> in order. Although, it is easy to confuse it with O (zero), so use <Y> as a special case.
P = April
Q = May
R = June
S = July
T = August
U = 9 Month
V = October
W = November
Z = December * <X> in order. However, since <X> and <Y> have already been used, it is speculated
that <Z> will be used in advance .
CLICK ON ITEM FOR MORE INFORMATION
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