Originally Posted by
RoadGuy
As freewheels gain gears (from 5 to 6 to 7 to eight), and the rear dropout width increases, the length of the axle that is unsupported (because of the design of the freewheel hub) grows, and as a result, 8-speed freewheel hubs break axles more often than 7-speed freewheel hubs, which break axles more often than 6-speed freewheel hubs, etc....
This is almost but not quite correct. 6 and 7-speed freewheels are almost exactly the same overall width and both use 126 mm rear dropout spacing so the unsupported axle length is the same for both. 7-speed cogs were just closer spaced than 6-speeds (except for the relatively rare Ultra-6 closely spaced freewheels). As noted, 8-speed freewheels are indeed wider than 6 or 7-speed freewheels and required a longer unsupported axle length under them.