Originally Posted by
dddd
That seems odd that they'd still put threads on the outside of the freehub body so late in time. Uniglide was long-gone from their lineup already, and it was never Shimano's practice to use other than HG cogs with STI shifters.
Perhaps even more odd is that I bought a road bike having the early 7s version of RSX (with "compact triple"), and it had an 11-24t, 7s cassette.
So it remains a mystery how that compact cassette would even fit on that supposedly-threaded freehub body. Perhaps the shop ground it down (a standard shop modification at that time) or maybe just kluged a spacer under the "compact" 11-24t cassette(???).
Does anyone else here recall what cassette size came fitted with your RSX 7s gruppo?
I can't tell from T-Mar's catalog photo.
I didn't keep that bike long enough to ever have to remove the cassette, I'd actually just bought it for a friend to ride. It was a Diamondback Expert and I still recall how particularly poor that the bike's spoke tensioning was.
The pictured CS-HG70-7 cassette is 11-24T. Those "compact" 11T HG cogs do fit. However, the spline channels do not run the entire width of the cog like on a 12T. If they did, the cog would probably split because the material between the channels and tooth valleys would be too thin. Instead, the spline channels stop about 2mm from the outside face, leaving a reinforcing lip directly under the cog teeth. This results in the cog overhanging the end of the freehub body by ~2mm. However on the HG-C freehubs the splines are actually relieved at the end of the freehub, allowing the cog to sit further onto the body. The diameter at the top and bottom of the splines is the same for both HG and HG-C freehubs.
Regarding the longevity of the dual compatibility 7 speed freehub, that would be a combination of marketing and economics. HG debuted in 1989, as 7 speed. RSX was Shimano 5th level road group and it took 6 years to trickle down that far. I don't consider that excessive. If you trickle it down too fast, you lose sales to from the higher groups, which have more profit margin.The longer you can use old tooling and the more groups you can spread it over, the more profitable it is. I don't think that Shimano's road groups got a dedicated, HG only freehub until Dura-Ace went 9 speed in 1997.