7 Speed Cassette Compatibility

ishay

Retro Guru
I have a couple of 7 speed LX rear hubs (560 and 563) with their original freehubs and I have two new HG41-7ac cassettes, neither cassette fits either freehub. There’s about 1mm of play between the 6 cog block and the small ring. I’ve tried a spacer at the back but the 2 rivets that (I’m guessing) hold the block together press onto it and skew the angle of the cassette. Are the modern HG41 cassettes not compatible with the old 7 speed freehubs? Or am I missing something?
 

ishaw

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I could be wrong but is this one of the differences between hg and ig? Not run 7sp since the 90s and can't remember much about the freehubs other than they had a threaded bit on the outside.
 

Paul R

Senior Retro Guru
its also a good idea to get a few different widths of spacer so you can play around untill you get it spot on
 

legrandefromage

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Oh the joys of the internet!

Forget UG/ HG/ IG and especially 'threaded' freehubs, its irrelevant!

Its just a spacer you need, there are no 'compatibility' issues otherwise you wouldnt even be able to slide the cassette on.

Some of the original Shimano 7spd cassettes required the multifit one between the cassette and the last cog before the lockring, some require it behind the cassette, onto the freehub first before the cassette goes on. Normally they come with the cassette

You most likely need the second one so it spaces and has the 3 cut-outs for the cassette assembly bolts that stick out.
 

ishay

Retro Guru
Ah of course, I’ve seen these before but never put two and two together.

And yes, the LX one does have the threads. Also pulled out an STX paralax today from a parts box which is subtly different, doesn’t have the threads and doesn’t need a spacer for the cassette…

4765B9D7-34B9-413E-844D-EB62EB9E32DA.jpeg
 

hookooekoo

Retro Guru
I’ve tried a spacer at the back but the 2 rivets that (I’m guessing) hold the block together press onto it and skew the angle of the cassette.
Possibly the spacer needs to have cut outs for the rivets*. I run 7-speed, but my 8-speed hub came with a spacer with the appropriate cut outs for a Shimano 7-speed cassette with rivets*.

* On my cassettes the 'rivets' are actually long bolts, and there are three of them spaced 120 deg apart. If you only have two 'rivets', is one of them missing? Is there a hole where the third 'rivet' should be?
 

hookooekoo

Retro Guru
I think the external threads on the freehub body were a hangover from Uniglide, which used a threaded sprocket to lock the cassette in place, rather than an internally threaded freehub body and an externally threaded locknut. Shimano persisted with the external freehub body threads for a while to give Uniglide backward compatibility (running 6-speed Uniglide cassettes on a 7-speed Hyperglide freehub body). However, due to the introduction of a wider spline, 7-speed cassettes/sprockets will not fit a Uniglide freehub body unless the wide spline is filed down.

This image is from Sheldon Brown, note that the middle image has both internal and external threads on the freehub body.

k7hub-3-stylessm.jpg


Also from Sheldon Brown:

People like to complain about Shimano's making things obsolete for "no reason" but that is not justified in this case. Older Uniglide splined sprockets can be used with no problem on the new bodies. Many older Hyperglide bodies also have the external threads that let you screw a Uniglide small sprocket on.
 

legrandefromage

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This is completely useless and irrelevant information!

The threads on the freehub body have nothing to do with cassette compatibility!!

The spacer required is for the cassette its self as it either needs spacing at the second from last cog OR before the cassette goes on

FORGET THE THREADS!!

FORGET UNIGLIDE!!!


ITS A CS-HG41-7 CASSETTE - SOME 30 YEARS AFTER UNIGLIDE WAS CONSIGNED TO THE 'IT WAS NICE SHIFTING BUT A THREADED COG WAS A GIT TO GET OFF' BIN

There, now you've made me use shouty capitals

This is the older HG-50 cassettes from years decades ago, you can see where the spacer goes. With a later cassette you need to replicate that with a spacer behind the cassette

1624343596201.png

 

ishay

Retro Guru
lol, it’s ok, I understand your point about my predicament, but the wider info is interesting all the same
 
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