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Old 03-19-18, 02:50 PM
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Introduction of 126 spacing and 7 speed

I tried to figure this out using Velobase and other references, but could not.

Some time around 1974 racing bikes began to switch from 120mm rear hub spacing to 126. 120 was the 5 speed standard, but would also accept "Ultra 6", which is 6 speeds at what later would be 7 speed spacing.

With 126, 6 speed freewheels could have 5 speed spacing, but was expanding the 5mm Ultra 6 spacing to 5.5mm really worth it to bike makers and component designers of the time? 6mm of extra axle was likely to increase axle breakage, and that would have been an issue.

So why the switch? Was it to go to 6 speed, and Ultra 6 was just something that came later to keep 120mm hubs relevent? Or was "Ultra 7" part of the deal, even though it didn't become common until over a decade later? When did the first 7 speed freewheel become available? Or was there some completely different reason that 126 came on the scene?
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