8sp cassette on 7sp hub ?

[KeepItSteel]

Am in the process of renevating an old and very tired 96 Kona Hahanna, have just spent 3hrs (I must be mad) cleaning and polishing the rear wheel and was planning to run a spare 8sp shimano cassette on it, it’s been donkeys since I spent much time on retro gear so I’ve forgotten most of the compatibility foibles.
I thought the cassette would be a straight swap for the 7sp version, clearly not, so my question is, if I remove the 12t cog can I run the 8sp cassette as a 7sp on the standard freehub without any alignment or other issues?

I’m guessing this wouldn’t work if I used the standard 7sp grip shifters, as there would probably be a cog spacing issue? But, Im planning on using a pair of XC Pro thumb shifters (8sp versions) and simply hooking them up as 7sp..

So, 8sp shifters and cassette running together in 7sp mode. Will this be ok?
Or is there a better work around other than finding an 8sp rear wheel/hub?

 

[FluffyChicken]

Re:

Change the freehub.

But what's the smallest cog, if 11T remove that and use a larger non compact lockring iirc.
You may need a thin space at the back still.
If the smallest is a 12T then dump the 17T or 14T and try that.
Or split it and loose the large cog.
Long time since I tried.

 

[KeepItSteel]

Smallest is 11t, I've dumped the 12t (iirc) and it seems to tighten together ok with the standard lockring. There's a minute amount of play I can feel, but I think it's more to do with the cheapo freehub rather than the cassette not fitting..

 

[pete_mcc]

7 and 8speed spacing is the same, it’s just the cassette overall width that’s different so you could ditch one cog and use it as a 7 speed with the 7 speed shifters. The spacing on,y really changed with 9 speed, that’s why XT thumb shifters with 7 speed could be used with 8 speed using the famous ‘hidden click’.

 

[FluffyChicken]

Re:

The 11T is compact and fits slightly differently. That's causing the world bobble. It would happen if you put it on an older non compact 8sp like M900.

(Assuming your 7sp is old and has the external threading on and isn't of the 'new' STX 7sp of the mid 90s)

Find a thin shim, perhaps a mm-ish.

 

[FluffyChicken]

7 and 8speed spacing is the same, it’s just the cassette overall width that’s different so you could ditch one cog and use it as a 7 speed with the 7 speed shifters. The spacing on,y really changed with 9 speed, that’s why XT thumb shifters with 7 speed could be used with 8 speed using the famous ‘hidden click’.

Not quite true, 7sp is 5.0mm, 8speed is 4.8mm
(Unless Suntour and the mix 5.0 and 4.8mm together for 8sp).
(1.2mm less over the full 7cogs you are using iirc)

The centeron (floating) pully and no ball bearing indexing take the slack up though ;-)

 

[pete_mcc]

Not quite true, 7sp is 5.0mm, 8speed is 4.8mm
(Unless Suntour and the mix 5.0 and 4.8mm together for 8sp).
(1.2mm less over the full 7cogs you are using iirc)

The centeron (floating) pully and no ball bearing indexing take the slack up though ;-)

You’re never more than .6mm out at any point over the cassette if you set up on the centre cog as you’re supposed to. So basically the same, and the reason why 8 speed shifters work perfectly on 7 speed cassettes and XT shifters worked on 8 speed cassettes.


If you need a Washer then SJS are always your friend:

https://www.sjscycles.co.uk/cassettes/s ... -11e-0300/

This washer often came with early 7 speed cassettes, I may even have one somewhere

 

[elite504]

Re:

All this is sound info. Why the 7 and 8 sp chains are the same. When the spacing gets properly different on 9s, that's when you start to need the narrower chain.

 

[KeepItSteel]

So for clarity, the additional 8th cog was just bolted onto the end of a 7sp block?

ie, they didn't close the gaps to squeeze another cog in the same width?

 

[Retro Spud]

Not quite true, 7sp is 5.0mm, 8speed is 4.8mm
(Unless Suntour and the mix 5.0 and 4.8mm together for 8sp).
(1.2mm less over the full 7cogs you are using iirc)

The centeron (floating) pully and no ball bearing indexing take the slack up though ;-)

You’re never more than .6mm out at any point over the cassette if you set up on the centre cog as you’re supposed to. So basically the same, and the reason why 8 speed shifters work perfectly on 7 speed cassettes and XT shifters worked on 8 speed cassettes.


If you need a Washer then SJS are always your friend:

https://www.sjscycles.co.uk/cassettes/s ... -11e-0300/

This washer often came with early 7 speed cassettes, I may even have one somewhere

Great info but there does that washer fit ?
I had one that came with a 7 speed cassette but would’t fit at the rear as the three mini bolt heads were in the way and at the front makes no sense

I fitted it at the rear after opening the holes up a little with a Swiss needle file