Future tech, could 12 spd solve the touring cassette problem

[Brucey]

if you recall I also commented that the most common thing for gearing gripes was not that the right parts didn't exist, more that bike/component manufacturers didn't fit them.

I'd argue that stupid cassette intervals are most often another example of that, rather than of an underlying need for more sprockets per se.

I'd also comment that it doesn't matter how you choose your 'modern gear ratios' you are doomed to end up with unevenly spaced ratios; as you go up the block you will go from 1-tooth gaps to 2-tooth gaps to 3 tooth gaps etc and each time the gear interval must change significantly. Griping about where exactly the jump from 2T intervals to 3T intervals occurs is just a reflection of poorly chosen ratios rather than anything else, and is a real YMMV issue anyway.

Suppose for a moment (just for sake of argument) that you ideally want gear ratio intervals that are more or less constant in percentage terms.

In mathematical terms you can't get integers that are a good approximation to a true geometric series SxZ^n (where S is the smallest sprocket) using S = 11 to 14T (say) and a small value of Z (say Z=1.1).

[This also means that when you have a chainring overlap, some of the gears will be additional useful ratios, but because they are also unevenly spaced (in a different way) there will also be duplicates and near duplicates on other chainrings. Most people can't remember the correct shift sequence to use with these intervening ratios, even if they claim that they would love to have (or derive actual benefit from) more closely spaced intervals; to me this says very clearly that they can't be that useful after all... ]

However, using a larger value of Z you can get pretty close to a good geometric series;

thus (for example) 13,16,20,25,31,39 is a very close approximation to a Z= 1.25 geometric series.

and 12,15,18,22,26,31 is a very close approximation to a Z = 1.20 geometric series

using that approach and a half-step chainring pair you can get 12.5% or 10% intervals respectively between your gears. And adding a third small chainring gives you a wide enough range. The very lowest ratios have intervals of 20% or 25% but actually that is probably OK; those are the kinds of gear intervals that you often need when climbing. As others have commented the half-step system has quite a lot going for it.

I personally don't like the double-shifts involved when using this kind of setup, and shifting five or more teeth a time at the back under load tends to get 'exciting' too. But I can see the attraction, for sure.

I have often wondered if we should be using a finer-pitch chain if we want better-spaced gear ratios. If we went to 1/4" pitch chain sprockets and chainrings of similar diameter could have geometrically spaced ratios with the same accuracy as the those above, but with half the interval in percentage terms.....You could of course achieve a similar effect by simply doubling the tooth count and sticking with 1/2" pitch chain, too. That such things have not been tried to my mind says that it shows that if there is a benefit to be had, it isn't big enough to be worthwhile.

cheers

[recordacefromnew]

Colin, reohn2, and me (http://cycleseven.org/customising-shima ... e-cassette) are among those who have found an 11T to be annoyingly useless on a wide ratio cassette, and also felt there to be an equally annoying jump between, say, the 18 & 21 or 17 & 20 sprockets....

I am not surprised by the extent of 11T bashing here, but am unsure if it is ever rational.

Perhaps you guys' front rings are too large, not the 11T being too small?

To my mind the only real disadvantage of a 11T is that it is a wee bit less efficient due to polygonal effect. But if it is not used much and if you don't race so what?

On the other hand, all else being equal having the 11T allows you to better utilise the rear mech wrap capacity (it eats up 1T of capacity rather than 3+T at the other end), it allows you to maximise sprocket range for a given rear mech (with associated max sprocket size capacity), and it lets you use smaller, lighter, stiffer and often cheaper front rings. It even lets you use a shorter, lighter chain and lighter cassette.

Depending on your requirement it might even let you run 2 rather than 3 (or 1 rather than 2) front rings!

[reohn2]

Colin, reohn2, and me (http://cycleseven.org/customising-shima ... e-cassette) are among those who have found an 11T to be annoyingly useless on a wide ratio cassette, and also felt there to be an equally annoying jump between, say, the 18 & 21 or 17 & 20 sprockets....

I am not surprised by the extent of 11T bashing here, but am unsure if it is ever rational.

Perhaps you guys' front rings are too large, not the 11T being too small?

To my mind the only real disadvantage of a 11T is that it is a wee bit less efficient due to polygonal effect. But if it is not used much and if you don't race so what?

On the other hand, all else being equal having the 11T allows you to better utilise the rear mech wrap capacity (it eats up 1T of capacity rather than 3+T at the other end), it allows you to maximise sprocket range for a given rear mech (with associated max sprocket size capacity), and it lets you use smaller, lighter, stiffer and often cheaper front rings. It even lets you use a shorter, lighter chain and lighter cassette.

Depending on your requirement it might even let you run 2 rather than 3 (or 1 rather than 2) front rings!

Bearing in mind we discussing touring gearing,I thought the problem had been explained quite well,a cassette with an 11t top needs wider gaps than many think acceptable in the most used cruising range to get low enough climbing gears,ie;9sp= 11,14,16,18,21,24,28,32.A preferable alternative cassette=14,15,17,19,21,23,26,28,32 with a big 46/48/50t big ring and two others @ 34t and 26t
I'd need a 36t big ring to make top anywhere near usable,which means less chainwrap=higher wear rates,and if used as a(Alpine)double c/set chainlines become extreme in the higher most used gears.Also IME 11t cogs feel rough through the pedals
So from a personal POV 11,12& to a lesser extent 13t cogs are useless.

[Brucey]

rather prosaically if you look through the available cassettes you have two choices in 11T -up cassettes

1) cassettes where it is paired with a 12T sprocket [ -which gives two gears very close together (in a touring context) bearing in mind these are 'gravy gears' anyway; you will be using them downhill with a following wind mostly occasionally so the effect on your average speed etc is slight in any event]

2) cassettes where it goes (more usefully) 11-13- but AFAICT all these cassettes have an 'annoying' 17-20 combination in them.

Also 11T sprockets IME

- run rough
- wear out quickly if you do use them
- are not efficient
- give you some kind of gear ratio you wouldn't want to use much anyway

So I can't remember when I last looked at a touring bike and thought to myself 'yeah, 11T sprocket, good choice'. More often I am thinking 'If I got rid of that 11T sprocket I could have a more useful large sprocket at the other end, another intermediate ratio, or reduced wheel dish'. In a touring context I would usually choose the last of these.

cheers

[recordacefromnew]

Bearing in mind we discussing touring gearing,I thought the problem had been explained quite well,a cassette with an 11t top needs wider gaps than many think acceptable in the most used cruising range to get low enough climbing gears,ie;9sp= 11,14,16,18,21,24,28,32.A preferable alternative cassette=14,15,17,19,21,23,26,28,32 with a big 46/48/50t big ring and two others @ 34t and 26t
I'd need a 36t big ring to make top anywhere near usable,which means less chainwrap=higher wear rates,and if used as a(Alpine)double c/set chainlines become extreme in the higher most used gears.Also IME 11t cogs feel rough through the pedals
So from a personal POV 11,12& to a lesser extent 13t cogs are useless.

Gap is such a personal thing so I am certainly not going to dispute what you prefer, but I do subscribe to what CJ and others said above, that 15% is close enough for touring and general purposes - in which case your range of 14-32 x 46/34/26 is also essentially achieved by 11-28 x 36/24, i.e. with only two front rings.

Am not 100% sure what you meant or entirely convinced by "less chainwrap=higher wear rates". Few cassettes are (or should be) worn because the smallest sprocket is, similarly I wouldn't expect the typical chain to be meaningfully more worn just because of the existence of a 11T or otherwise.

rather prosaically if you look through the available cassettes you have two choices in 11T -up cassettes

1) cassettes where it is paired with a 12T sprocket [ -which gives two gears very close together (in a touring context) bearing in mind these are 'gravy gears' anyway; you will be using them downhill with a following wind mostly occasionally so the effect on your average speed etc is slight in any event]

2) cassettes where it goes (more usefully) 11-13- but AFAICT all these cassettes have an 'annoying' 17-20 combination in them.

Touring or otherwise it does not make sense to have wide gaps at the small sprockets - in those gears air resistance dominates and increases with the square of speed, while power requirement is cube! Wide gaps should be reserved for the large sprockets to avoid frequent changes losing momentum when the going gets tough uphill.

Regarding cassettes, even if we have to stick to the 15% gap limit throughout, starting with 11T the logical progression is 11/12/13/15/17/19/21/24/28 for 9 and 11/12/13/15/17/19/21/24/28/32 for 10 speed. Both are available from sram e.g. as PG950 and PG1070 respectively straight out of the box.

Also 11T sprockets IME

- run rough
- wear out quickly if you do use them
- are not efficient
- give you some kind of gear ratio you wouldn't want to use much anyway

So I can't remember when I last looked at a touring bike and thought to myself 'yeah, 11T sprocket, good choice'. More often I am thinking 'If I got rid of that 11T sprocket I could have a more useful large sprocket at the other end, another intermediate ratio, or reduced wheel dish'. In a touring context I would usually choose the last of these.

cheers

Apart from the polygonal effect which I did mention, I see no reason for a 11T to run noticeably rougher than e.g. a 12T in the same position and therefore having the same chainline. However, iirc you advocate/use non-standard bb spindle length to move the whole chainset further inboard than what standards dictate - in that circumstance your small rear sprocket may well run rougher than it should...

[Brucey]

Touring or otherwise it does not make sense to have wide gaps at the small sprockets - in those gears air resistance dominates and increases with the square of speed, while power requirement is cube! Wide gaps should be reserved for the large sprockets to avoid frequent changes losing momentum when the going gets tough uphill....

Well I disagree with the first (you are clearly thinking of racing...) and better agree with the second. As I described earlier, when touring the high gears are 'gravy gears' for use on downhill and/or downwind stretches. Exact gear ratios -and therefore gearing intervals- are far less important here.

The most simple analysis (which you have seemingly not carried out) clearly indicates that when touring expending great -or even 'normal'- effort under these (downhill/downwind) conditions is not an efficient use of your energy resources; if you pedal at half or three-quarters of the usual effort, at the 'wrong' cadence you are losing next to nothing speed-wise and there is very little more to gain under such conditions. No-one rides at constant output all the time and riding downhill/downwind at full output is usually a bad choice.

Your argument better applies to the conditions that prevail most of the time which are flatter roads with small gradient changes and significant changes in resistance through headwind. Thus the place you might gain through having gears closer together is arguably the midrange. Even then as CJ describes you are down to 1% tops or something like that to gain if you reduce the gear interval below about 15%.

My idea of a satisfactory pair of small sprockets for touring is something like 15, 13. This upshift is a little over +13%; more than adequately close for touring purposes. Having 1T intervals anywhere on a touring cassette is pretty much a complete waste of time, and having any gear that you can pedal faster than 30mph is similarly of next-to-no benefit.

There is in fact very little to commend the use of smaller sprockets etc for touring;

- they are less efficient (every gear you use)
- they wear faster (every gear you use)
- the stress on the chain is higher (every gear you use)
- gearshifts are slower (every shift)
- they run rougher more of the time
- the weight difference is insignificant
- you are inevitably lumbered with less evenly spaced gear ratios
- you are more likely to be using an MTB-based transmission with a high Q value.

The only time I'd really contemplate it would be if I genuinely couldn't get enough gear range any other way, or there were some other special requirement (like ground clearance). But we are spoilt for choice in terms of mechs etc these days so for solo use I just can't see it happening anytime soon, not for me. Trikes and expedition tourers may be special cases but even then there are other ways of getting the range you need; the small improvement you might get through using smaller chainrings and sprockets all round mightn't be enough anyway.

No wonder then that (IIRC) having examined it carefully a leading bike publication came out in favour (overall) of larger chainrings and sprockets for touring purposes.

YMMV of course but if you propose any reasonable touring transmission with small sprockets, I'd expect someone to be able to come up with one that was better in many or most respects that used slightly larger ones.

cheers

[reohn2]

Gap is such a personal thing so I am certainly not going to dispute what you prefer, but I do subscribe to what CJ and others said above, that 15% is close enough for touring and general purposes - in which case your range of 14-32 x 46/34/26 is also essentially achieved by 11-28 x 36/24, i.e. with only two front rings.

But the gaps in the most used ratios are wider with your selection are 12.5 & 16.7%, mine are between 9.5 and 13%,and whilst the range is there for sure,the choice and progression isn't.

Am not 100% sure what you meant or entirely convinced by "less chainwrap=higher wear rates". Few cassettes are (or should be) worn because the smallest sprocket is, similarly I wouldn't expect the typical chain to be meaningfully more worn just because of the existence of a 11T or otherwise.

My meaning was less sprocket and chainring teeth on less chain=less chainwrap so higher chain wear.
And more extreme chainlines due to there being only two chainrings.
My chain in the most used gears ie; outer of three rings in 4,5,6&7 cassette positions is running just either side of straight,exactly straight being between 5&6.
With your double set up,I'd be using middle position for the outer,and those similar ratios would mean straight chainline would be at cassette position 3 most used cogs would be 4,5,6&7.
I admit that if I were to set the drivetrain up from scratch I'd use a longer BB axle(square taper)the present one is 115mm,so to get a straight c/line in the most used cogs it'd need to be at least 122mm, which would alter the Q significantly enough for even me not to want to do it,and even then it wouldn't be ideal.
Or I'd need to search for the 'right' chainset to achieve good Q and good chainline,again something I'm not prepared to do for no gain,only loss.
I am of course arguing from a personal POV which all I can do,some may find 15% gaps OK,they don't suit me one bit and top two gears are for as Brucey says 'gravy train' gears.

[james-o]

12s.. no, thanks anyway .. 9 or 10 is plenty. I'm not convinced that I need the exact ratios and small steps more gears offer. Shimano seem obsessed by the idea that we need to maintain a cadence and shift accordingly. I'm happy at 50 rpm or 100 or so. Just slow down a tad and use the highest gear that isn't stressing the legs too much, or go up a gear and push on. I just want range and reliability. Anything under 13 or 14T is a liability on long muddy rides or long distances between cleaning and much over 28 or 32 seems like a fix for an inner chainring that's too big. To that end I've had some really good results from a Hope SS hub with 6x 9spd cogs on it (a Jeff Jones inspired set up) and a 50mm chainline MTB triple up front, 22-32-44. 18spd with 9spd kit. It avoids the crazy chainlines at extreme gears so I can use all the gears, appreciated there's cross-overs but setting the front based on the general terrain / fatigue etc and being able to use all 6 on the rear with good chainline works well. Usually have a 12-14-16-19-21-25 or a 14-16-19-21-24-28. I've used the 17-34 block-mounted part of an XT cassette for more tricky off-road rides. I use those cheap Deore 9s cassettes that I can unscrew and find that the complex shift ramps still seem to do a good job when they're not aligned exactly as intended. I've used a few single-speed cogs stacked up alongside normal 9s cogs with a single ring up front when I've wanted really good durability. Doesn't shift too well but it's not as bad as you'd expect. The Hope SS hub means the rear wheel's dishless.

[Tonyf33]

I see that some folk are missing the point of the thread, what having those extra sprockets on a cassette could offer and not taking into account perceived durability/cost issues.
Blithely going on about an 11T (or indeed a 12) sprocket being of no use except for racing ( ) and even more so on a 8, 9 or even 10 speed set up when that's exactly what a 12 speed cassette could allow (in theory IF they were made) those whom want/can use a smaller sprocket still have a good sized low gear sprocket as well AND not have 15-20% jumps between ratios.

If you're happy with those size jumps, knock yourself out, personally I like having a relatively small jump, on a incline with a load keeping a certain cadence makes life easier, it makes it more relaxing and when you're tired I don't want a big jump whichever way you're going. For some people I'm sure they are happy with the bigger jumps, me (and I'm sure plenty of others) aren't.
IF given the choice and that IS the point of thread I'd rather have what I've described. And in the range of what many people touring use an 11-30, 12-32 or a 13-34 over 12 sprockets would fill in some very useful gaps that just wouldn't be available on an 8/9/10 speed system.

Maybe not so much a problem but IMO it would make life easier and not just for touring.

It was a hypothetical scenario one that seems to have created debate and showing that many people are encamped in their way of thinking/how they go about things , it also shows that people aren't able to accept that others like to have things different to them or the accepted 'norm' Personally I don't think we need to think about 12 speed cassettes for some time to come, but If it becomes viable in the future with thought out options for tourists/audax, is reliable, relatively durable and not so costly (105 11 speed is under £300 for a groupset) then I'd be interested for a touring set up..

[reohn2]

Tony
Sorry about the thread dift,don't know how it happened
But I believe people on a fairly conservative touring forum aren't going to think outside of the (max) 10sp box,if they find their present set up works so well for them.
I believe ultra narrow chains were mentioned early on,and despite you mentioning durability and cost not coming into it,durability is an integral part of a touring bike,cost perhaps less so but a consideration for most.
So that said if either of those two factors weren't a problem would I welcome a 12 speed cassette?
No,as it wouldn't offer me anything more than my custom 9sp cassettes and triple chainsets.
I'm as happy with the gaps as I am with the range.

But if electronic shifting were ultra reliable,cost effective(say run off long lasting AA batteries lasting six months or more) with shift buttons that could be placed anywhere on the handlebars,say in three positions per side,then I could be swayed.
We can all dream

[Brucey]

I'm sure there are people who would 'like more gears'.

However 'liking' is one thing but measureable benefits are quite another. And to assume (even for sake of argument) that there won't be any durability issues is a bit of a stretch....

As CJ has pointed out we have a nice broad torque curves so past a certain point we don't really gain any significant benefit from more closely spaced gears. This tallies well with the cycling I have done.

YMMV of course but someone 'liking something' isn't exactly a major benefit (except to those trying to flog new gear to the more impressionable of us...). After all, people 'like more' of all kinds of odd things like booze, fags, shiny trinkets, drugs, payday loans, fatty foodstuffs and even 'strictly come dancing' ....

Arguably any of these is OK in moderation but some folk don't know when or how to stop themselves; so it is with gear ratios....

cheers

[recordacefromnew]

Touring or otherwise it does not make sense to have wide gaps at the small sprockets - in those gears air resistance dominates and increases with the square of speed, while power requirement is cube! Wide gaps should be reserved for the large sprockets to avoid frequent changes losing momentum when the going gets tough uphill....

Well I disagree with the first (you are clearly thinking of racing...) and better agree with the second. As I described earlier, when touring the high gears are 'gravy gears' for use on downhill and/or downwind stretches. Exact gear ratios -and therefore gearing intervals- are far less important here.

The most simple analysis (which you have seemingly not carried out) clearly indicates that when touring expending great -or even 'normal'- effort under these (downhill/downwind) conditions is not an efficient use of your energy resources; if you pedal at half or three-quarters of the usual effort, at the 'wrong' cadence you are losing next to nothing speed-wise and there is very little more to gain under such conditions. No-one rides at constant output all the time and riding downhill/downwind at full output is usually a bad choice.

Your argument better applies to the conditions that prevail most of the time which are flatter roads with small gradient changes and significant changes in resistance through headwind. Thus the place you might gain through having gears closer together is arguably the midrange. Even then as CJ describes you are down to 1% tops or something like that to gain if you reduce the gear interval below about 15%.

Really? I don't think I need to do any analysis, given you hit air resistance dominance in no wind condition at ~10mph, while burning only around 30W on average. You shouldn't need downhill, following wind or raining gravy etc. to experience the fallacy of large gaps in small sprockets.

[Brucey]

Really? I don't think I need to do any analysis....

uh huh...

cheers

[531colin]

Colin, reohn2, and me (http://cycleseven.org/customising-shima ... e-cassette) are among those who have found an 11T to be annoyingly useless on a wide ratio cassette, and also felt there to be an equally annoying jump between, say, the 18 & 21 or 17 & 20 sprockets....

I am not surprised by the extent of 11T bashing here, but am unsure if it is ever rational.

Perhaps you guys' front rings are too large, not the 11T being too small?.........

Ok, I have 12 or 13T smallest sprockets, 34T largest.
Chainrings 24/34/46 or 22/32/44
My top gear is quite high enough for me, I use bottom gear more often than top.

What rational use do I have for an 11T? I wouldn't mind trying 18/26/36 or something like that at the front with an 11T at the back.....

I simply can't handle a 17/20 jump when I'm trying to make progress....28/34 when I'm going at walking pace or less is fine by me.

[Tonyf33]

Tony

But if electronic shifting were ultra reliable,cost effective(say run off long lasting AA batteries lasting six months or more) with shift buttons that could be placed anywhere on the handlebars,say in three positions per side,then I could be swayed.
We can all dream

Oh yes, flat bar/drop bar electronic triple shifting that is accessible from almost any hand position would be fantastic. Di2 packs (500maH) seem to get about 40-60 hours of use (And often much more) from those reporting it but a AA powered unit could be useful. With 500 charge/discharge cycles for Li-ion fairly common place that's about 20,000 cycling hours before your battery needs consideration for replacement.