Difference between 8-sp and 9-sp cassettes?

cdaly_

So, is the only difference between an 8-sp and a 9-sp cassette in the thickness of the spacers?

Reason I ask is my winter tyres will not fit my bike but will fit my wife's which has 7-sp shifters. Now, the 8-sp cassette shifts nicely (over 7 of the gears) on her bike but it's totally worn out so that the chain is skipping.

I have a retired 9-sp cassette (retired for range rather than wear) which I could use if the spacing was right. Could I just swap a couple of sprockets between the 8-sp and 9-sp cassettes and retain the 8-sp spacers and expect everything to work?

bcmf

new bike needed.





















Come on.....its been a while since anyone said it!:rolleyes:

cdaly_

Deffo. Only trouble is new bike is more likely to be a better road bike so neither bike will fit the winter tyres...

ednwireland

1-sp

bcmf

well if you bought a new bike it would probably have tyres on it!

Holyboy

cdaly_ wrote: »

So, is the only difference between an 8-sp and a 9-sp cassette in the thickness of the spacers?

Reason I ask is my winter tyres will not fit my bike but will fit my wife's which has 7-sp shifters. Now, the 8-sp cassette shifts nicely (over 7 of the gears) on her bike but it's totally worn out so that the chain is skipping.

I have a retired 9-sp cassette (retired for range rather than wear) which I could use if the spacing was right. Could I just swap a couple of sprockets between the 8-sp and 9-sp cassettes and retain the 8-sp spacers and expect everything to work?

There's a few things you could do but none are ideal, you could fit 8 of the 9 speed sprockets on to the freehub, doing away with the largest one but it would mean running a 9 speed chain and shifter or friction shifter, or you could fit seven of the sprockets using old 7 speed spacers, the only problem will be the last two sprockets that have in built spacers, these would need some small shims to get the spacing right, it's all a bit messy,I say new bike is really needed too.

bcmf

Holyboy wrote: »

I say new bike is really needed too.

Its unanimous so!

cdaly_

Holyboy wrote: »

There's a few things you could do but none are ideal, you could fit 8 of the 9 speed sprockets on to the freehub, doing away with the largest one but it would mean running a 9 speed chain and shifter or friction shifter, or you could fit seven of the sprockets using old 7 speed spacers, the only problem will be the last two sprockets that have in built spacers, these would need some small shims to get the spacing right, it's all a bit messy,I say new bike is really needed too.

As far as I can tell, the spacing on a 7-sp and an 8-sp is the same. New 7-sp cassettes appear to come with an extra spacer to fit them on 8-sp freehubs. The worn out 8-sp cassette seems to be shifting fine with the 7-sp shifters on the bike which seems to confirm the theory.

The 9-sp would have narrower spacing but, as the internal dimension of the chain is the same, I reckon I should be able to use an individual 9-sp sprocket with 8-sp spacers to get the same shifting position. I'd probably hold on to the 8-sp 11t and 12t as these are not very worn and would probably not get used that much*.

The whole idea of this is to be able to just pop these wheels on my wife's bike on a snowy morning without mucking around with the bike's existing setup.

* This wheel would be the permanent home for the winter tyre and would only get used in the snow/ice...

Holyboy

The spacing is slightly different on 7, 8 and 9 speed I have pages and pages of measurements but not here it's all in work! You could always use 2, 3, 4, or 5 of the sprockets with seven speed spacers and adjust the limit screws, or just get a new 7 speed cassette and chain, I suppose it's just down to how well you want it all to work, with the 9 speed sprockets and 8 speed spacers you could probably get it to shift ok(sort of), except in the two smallest, I guess it's just a matter of how fussy you are about it working well or just working(ish).

cdaly_

So I went and tried it. Swapped out the 4 middle sprockets from the 8-sp and swapped in the matching 4 from the 9-sp. Kept the 8-sp spacers.

Quick test spin (in the howling wind and rain) seems to be shifting ok. Not quite perfect, there's an occasional non-shift going up one gear followed by a double-shift for the next but adequate for my intentions.

I'll pick up a cheap 7-sp cassette at some stage but in the meantime I appear set for the snow / ice this winter.


This means, of course, that we'll have mild winters for the next 5 years...

cdaly_

So I took the winter tyres on the commute this morning (to bed in the spikes). Sounded like cycling on bubble wrap.

Gearing worked nicely with 9-sp sprockets and 8-sp spacers in an 8-sp cassette with 7-sp shifters...

ednwireland

cdaly_ wrote: »

Gearing worked nicely with 9-sp sprockets and 8-sp spacers in an 8-sp cassette with 7-sp shifters...

cdaly_

You'd have to read the first post.




And it's all about the hacking, anybody could buy the bits they need. Making them up out of what you have is so much more fun...

ednwireland

cdaly_ wrote: »

You'd have to read the first post.




And it's all about the hacking, anybody could buy the bits they need. Making them up out of what you have is so much more fun...

yep my commuter has a chain made of 7 and 8 speed links and it works fine !