Originally Posted by
Exit.
I thought that freewheels were always 126mm, and freehubs were always 130mm. ie. the change in hub design precipitated the change in dropout spacing. I could be entirely wrong, though
No, 120mm spacing was standard for 5-speed freewheel hubs. SunTour introduced their "Ultra-6" freewheel in the early 80's that packed 6 cogs into the same with as a traditional 5-speed cluster, but other companies (i.e. Regina, Zeus, etc.) were already making 6-speed clusters in the mid 70s. These used a standard (same as 5-speed) cog spacing that required the 126mm OLD. A little thought brought the realization that using the "Ultra" spacing with a 126mm OLD allowed a 7-speed cluster. 8-speed bumped the OLD to 130mm, and so on...
Shimano's first freehub design was 126mm OLD, IIRC.