I’m building up an early 90’s Hardrock for the girlfriend and one thing that has always confused me is cassette size and width. This is a 3×7 from the factory but can I put an 8 speed (specifically a Microshift acolyte 12-42) cassette on here as long as I match the derailleur and shifter with an 8 speed microshift ? Rear axle spacing is 135mm.
I always assumed boost spacing created more room for the 11-12 speeds that are newer. But I never mastered like if a 7speed hub is smaller than an 8speed or if an 8 speed cassette is “tighter” and the chains are slightly narrower.
I know I’m probably going to linked to Sheldon brown but would love some input. thanks !
by gentle_doom
1 Comment
Short bodied 7 speed freehubs don’t work with 8/9/10 cassettes. There are hacks for replacing the freehub body or using only 8 cogs of a 9 speed cassette, but the guaranteed solution is a new wheel with a 8/9/10 speed HG freehub.
As you predicted, some reading here from [Sheldon](https://www.sheldonbrown.com/k7.html#up7) but RJ also explains [here](https://m.youtube.com/watch?v=n5YkkAP_QVI).
Yes, the spacing gets tighter between cogs on 9/10 speed cassettes, but the overall width of a 7 speed cassette is a few mm shorter as well
https://www.sheldonbrown.com/cribsheet-spacing.html