VeloBase.com - Component: SunTour BB-400, Cyclone

SunTour (Maeda)

SunTour derailleurs have a two-letter date code. On rear derailleurs the code is stamped on the back side of the inner parallel arm. On front derailleurs it is stamped on the back side of the inner cage.

The first letter represents the year. Larry Osborn and I believe O (Oh) is 1972, V is 1979 and A is 1984. As with Shimano, the second letter is the month code, where A is January and L is December.

SunTour Year Code

N	O	P	Q	R	S	T	U	V	W	X	Y	Z
1971	1972	1973	1974	1975	1976	1977	1978	1979	1980	1981	1982	1983

A	B	C	D	E	F	G	H	I
1984	1985	1986	1987	1988	1989	1990	1991	1992

SunTour Month Code

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

The earliest Suntour derailleur I have found with a code is marked OF. A rear derailleur marked OD (corresponding to April of 72) was reported by Leighton Walter. I have a bike that dates from between 1970 to 1972 that has the original SunTour derailleurs. These derailleurs do not have date codes on them, so I believe the coding started sometime between 1970 and April of 1972.

(source: vintage-trek.com)