shimano cassettes - 7-speed good : 8-speed not so good

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rmurphy195
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby rmurphy195 » 4 Feb 2019, 9:42pm

The problem with fitting smaller chainrings is that the front changer has to sit lower - which may leave it fouling the chainstay, If you don't have a band-on front changer then you may not have as much scope to change.
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andrew_s
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Re: shimano cassettes - 7-speed good : 8-speed no so good

Postby andrew_s » 4 Feb 2019, 9:43pm

hondated wrote:Particularly if my understanding is correct the 7/8 chains last so much longer.

I never found much difference between 7 and 8 speed in terms of wear.

The big step was between 6 speed Uniglide and 8 speed Hyperglide.
I don't suppose that there was much difference in chain wear, but the Uniglide sprockets had proper full size teeth, and would tolerate something like double the wear that would cause chain skip on 8 speed Hyperglide

zenitb
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Re: shimano cassettes - 7-speed good : 8-speed no so good

Postby zenitb » 4 Feb 2019, 11:04pm

Graham wrote:
ZenitB : thanks this is very useful to know that the Sunrace cassettes 12t-32t : 8 speed, are available.


Cheers Graham...there is also a (budget) Shimano option..unplated but probably the same cogs... (see pic)..about the same price as the Decathlon/Sunrace option. It looks like 8 speed ain't dead yet. .which is good because both my touring bikes are 8 speeders !! :-)
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Sweep
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Re: shimano cassettes - 7-speed good : 8-speed no so good

Postby Sweep » 5 Feb 2019, 7:28am

Brucey wrote:
inevitably shimano will stop doing a full range of cassettes in the future but other manufacturers will fill any real niche I would imagine.

cheers


Can I ask who you consider to be decent other manufacturers brucey? I ask as I have 2 7 speeds (one paired with a 3-speed dual drive hub) one 8, and the rest 9 and won't be going any higher if I can help it. I imagine in time 8 and 9 will face the same challenges.
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Brucey
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Brucey » 5 Feb 2019, 7:42am

workable cassettes are made by IRD, Sun Race, Ventura, as well as shimano and sram. I think there are others too.

[edit; add DNP, BBB, ETC, Sunlite, One23, to brands that offer 7s. Some will of course be rebrands of others.]
[BBB offer a 12-32 7s cassette BCS-07S but it has a big step in it, going from 24 to 32T]

It always seems slightly ironic to me, that one of the big plus points of having a freehub was that you could have whatever sprockets you wanted, and swap them about easily. However it turns out that folk are somewhat unlikely to actually do that, preferring to buy cassettes in one lump. ….

cheers
Last edited by Brucey on 5 Feb 2019, 7:11pm, edited 3 times in total.
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Samuel D
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Samuel D » 5 Feb 2019, 8:24am

Brucey wrote:It always seems slightly ironic to me, that one of the big plus points of having a freehub was that you could have whatever sprockets you wanted, and swap them about easily. However it turns out that folk are somewhat unlikely to actually do that, preferring to buy cassettes in one lump. ….

I’d happily buy loose sprockets if they were available and cost-effective, but as far as I can tell they’re neither. Scavenging for parts with a drill and multiple cassettes is not my idea of a good deal and produces much waste.

The other thing is that the Shimano shift aids designed for specific adjacent sprockets are worse than no shift aids when you have the wrong adjacent sprocket. They appear to work tolerably anyway, but this weighs on my mind when considering the overall appeal of this approach.

I’m lucky to find the 8-speed Shimano 13–26T cassette just about perfect for my needs anyway. These were available at very low prices in recent years but prices are going up and several online shops no longer stock this part (and no high street shop has it). I’d be surprised if you could find them at current prices in a couple of years, so I bit the bullet last month and got several of them. At about six chains per cassette, they should last me a long time.

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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Nigel » 5 Feb 2019, 11:51am

Samuel D wrote:......I’m lucky to find the 8-speed Shimano 13–26T cassette just about perfect for my needs anyway. These were available at very low prices in recent years but prices are going up and several online shops no longer stock this part (and no high street shop has it). I’d be surprised if you could find them at current prices in a couple of years, so I bit the bullet last month and got several of them. At about six chains per cassette, they should last me a long time.


Thanks for the warnings. I'll be off shopping shortly for stocks as well. My old tourer runs 13-26, with a 24-46-48 chainset. Slightly odd-ball in the setup, but works for me.

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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Brucey » 5 Feb 2019, 1:55pm

when it changed from UG to HG the system became a lot less flexible because of the ramps and gates having to line up in order to be of any benefit. UG was a lot less fussy but I suppose it did result in fairly clunky shifting by comparison.

I can't help but think that the campagnolo idea they used on their first cassette hubs (of having sprockets that could be put different ways onto a symmetric spline so that they would line up with their neighbours and therefore shift OK in different combinations) was basically a good one. With a suitably fine spline (18T rather than 8T or 9T say) I don't think there would be any great need for multiple variants of each sprocket size.

The penalty would be that assembling each cassette would be a bit more fiddly. Again this need not be an insurmountable problem; it just needs some thought given to spacers/clips/bolts etc, so that if necessary the assembled cassette can stay as one lump when it is removed.

It occurs to me that a UG spline could be modified to have 18 splines (not quite evenly spaced) such that the new bodies would accept the old sprockets (HG with the timing feature removed) and old UG bodies would (again with a small adjustment) accept the new sprockets.

cheers
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Samuel D
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Samuel D » 5 Feb 2019, 2:24pm

Merlin Cycles had a good price when I bought my 13–26T cassettes, Nigel.

Brucey wrote:I can't help but think that the campagnolo idea they used on their first cassette hubs (of having sprockets that could be put different ways onto a symmetric spline so that they would line up with their neighbours and therefore shift OK in different combinations) was basically a good one.

That does sound attractive to me, but history shows that minor improvements in convenience always win in the end. The incremental improvement – the fractionally better shifting, the thinner iPhone, the electronic driving aid – is often insignificant in itself, but several of them add up to a significant improvement over time.

Still, shift quality is not as important to me as to the market at large. I just want the shift to happen reliably when sympathetically commanded. Others seem to want to shift under 1000 W of pedalling power.

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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby fastpedaller » 5 Feb 2019, 2:30pm

An idea (I think I'm correct) is to grind off the 'wide part' of a sprocket to enable it to be fitted in other positions. If using a sprocket from another cluster it can then be put in the correct position (in its new 'home') for the ramps to work as intended. It would be a more beneficial (as long as there is an indexing mark) for the freehubs to be as the old UG pattern (ie without the narrow timing feature) - however I can see this could cause issues if a customer isn't fully aware. Without the ramps and other features the the sprockets could be turned over to double the wear (as in UG), but a lot of the gearchange quality would be lost - I guess we can't have it all ways!

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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Brucey » 5 Feb 2019, 2:51pm

it is easy enough to modify HG sprockets to fit onto a UG spline (or in any position on an HG spline), but this only gives you angle increments (between neighbouring sprockets) of 40 degrees which isn't quite good enough to get really good alignment of ramps.

Campag's system used 8 splines and this gave 45 degree increments; nowhere near good enough. They needed different versions of many sprocket sizes (with different ramp positions) to make up for this and maintain good shifting. If they had chosen a finer spline they wouldn't have needed to do this. The sprockets were all loose so once the cassette was removed the timing of each sprocket would easily be lost.

I think the 'loose sprocket problem' ought to be fixable, so that the cassette can remain in one piece (and be cleaned, handled etc) without the timing of the sprockets being upset; it just needs a little creative thought to be applied. This would render the system as convenient for most users as at present whilst offering flexibility for those who want/need it.

cheers
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby MikeF » 5 Feb 2019, 10:07pm

It's interesting to note that 11-34 sprockets on 8 speed Shimano HG50 cassettes do not have the same teeth as Shimano HG41 (HG31) cassettes.
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deliquium
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby deliquium » 7 Feb 2019, 9:47am

5 of my bikes have 8 speed 13-32 custom cassettes.

CS-HG50 13-28 7 speed (cheap from Germany) de-rivetted and dismantled + whatever the cheapest Shimano 8 speed cassette happens to be at the time (as long it's silver and has a 32 sprocket. De-rivet the 8 speed cassette, bin the 7 unwanted sprockets and 7 speed HG50 spacers and reassemble using the 32 and the 8 speed spacers* together with the 7 speed 13-28 sprockets.

The 7 speed 13 sprocket (with its solid inbuilt spacer) is no problem with regard indexing.

* NB not all the 8 speed spacers are the same thickness - even on the same cassette! But it's not that critical in real life :)
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mig
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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby mig » 7 Feb 2019, 10:01am

Brucey wrote:when it changed from UG to HG the system became a lot less flexible because of the ramps and gates having to line up in order to be of any benefit. UG was a lot less fussy but I suppose it did result in fairly clunky shifting by comparison.


clunky as in 'not very good' ? or to mean 'it goes 'bang' and it's in gear'?

i actually quite like the latter. most of my geared riding has been in TTs when i'd positively want to know that the bike was in gear and the chain was solidly on the sprocket. then i could just concentrate on getting along the road.

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Re: shimano cassettes - 7-speed good : 8-speed not so good

Postby Brucey » 7 Feb 2019, 10:35am

mig wrote:
Brucey wrote:when it changed from UG to HG the system became a lot less flexible because of the ramps and gates having to line up in order to be of any benefit. UG was a lot less fussy but I suppose it did result in fairly clunky shifting by comparison.


clunky as in 'not very good' ? or to mean 'it goes 'bang' and it's in gear'?.


a bit of both I suppose. Mind you some of the shifting benefits with modern kit come from cleverness with the chain as well as the sprockets. I occasionally asssemble a system using a mishmash of parts just to see how it runs. I have been pleasantly surprised by such arrangments as using

- 6s HG-esque freewheels in 6s systems (very positive and much smoother than one would expect, using 8s chain)
- 7s UG sprockets in an otherwise modern (8s chain and modern mech) system (again positive but not as smooth under load, and less tolerant of mech wear etc than with HG sprockets)

cheers
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