Originally Posted by
balindamood
Sixes first appeared in the early 70's, "ultra" or narrow sixes by mid to late 70's. Narrow sevens came out in early to mid-80's, and started to show up on upper end bikes by mid to late '80's.
At least for SunTour, narrow six and seven happened simultaneously, on the same system. I distinctly recall the display with bodies, cogs, spacers, and charts hanging on the wall of my local dealer in Northampton, Mass. I used to build my own blocks. They used the same body but with different small cogs. For seven, the last cog screwed into the inside of the sixth, or something like that. It's been a long time since took one apart.