On Thursday, June 10, 2021 at 11:34:07 AM UTC-7, Luns Tee wrote:
On Thursday, June 10, 2021 at 11:18:34 AM UTC-7, AMuzi wrote:
On 6/10/2021 10:58 AM, Luns Tee wrote:
For proper 6 speed bodies, yes, the outer shell (that sprockets stack up on) is shorter than for 7 speed; I was referring to support of 6 speed on 6/7 speed freehubs, so as not to imply that 6 and 7 are inherently the same thing.

That's just the outer shell though. The inner core of the freehub (the part that mates with the hub shell) was identical for 5 and 6 speed (at least for FH-6207/8) and in my experience 7 speed too. This means that if you need to replace a failed 6 speed freehub body, you can directly replace it with a 6/7 speed freehub body without affecting the OLD. This does not necessarily mean you can use a 7 speed cassette on said body; the first position sprocket can end up too close to the dropout.

The 5 speed freehub body shell was just long enough to enclose its core with only a thin dust shield. Going to 6 speeds, the shell was longer, allowing for either a better seal, or space for a hyperglide lockring with a thin dust shield similar to what was used for 5 speeds. The shell got even longer for 7 speed, allowing for better sealing together with hyperglide support.

-Luns

Yes, very clear overview.
Modern 8+ CS bodies can mount in place of the seven or six
version.
Indeed. Seal and corresponding cone and/or axle spacers often have to be changed together with the body, but it's sometimes avoidable. The 8HG/UG-speed body from 6402 will mate fine with the cone and seal used in the 6/7UG 6400 hub, although the spacer between the cone and locknut is 0.7mm thicker for 8 speed usage.

Going between 6 and 7 speed, the 7HG/UG body from the FH-HG50 hub is a perfect replacement for FH-6207/8 and 1050, with its metal dust cap having an identical seal diameter as the plastic dust shield it replaces.
I'm not sure that any 5 cassette hub supported that hub-body
interface format (just don't know either way)
https://si.shimano.com/api/publish/s...208-5-0733.pdf
The original HG bodies were double threaded to accept both
UG and HG cassettes.
Yep.

The 7sp DuraAce 7400 (or that series) had a threaded freehub body that, AFAIK, is not compatible with any modern 8+ bodies. I have that hub with all the Fisher Price stack-em-up cogs. All sitting in a box.

-- Jay Beattie.