Practical limit for number of rear cogs in the future?
05-30-17, 12:42 PM
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I'm hoping the "enthusiast" level groups (e.g. Tiagra and Sora) won't go past 10 speeds and will keep triple cranks. With a triple crank you can really achieve an extremely wide gear range with satisfactorily tight gaps between gears with a nine speed cassette.
The "need" for more cogs is driven primarily by compact double and single ring cranksets. Selling a compact double to someone who really needs the low gearing of a triple requires a wide-range cassette. A wide range cassette enables a good marketing narrative for more cogs to achieve small gaps in the gearing. With a single ring crank wide gearing is even more necessary and so the push for more cogs is proportionately compelling.
Using a compact double with 50-34 chainrings, when the chain is on the small ring it will rub the big ring at around 2.3 degrees, which eliminates the two smallest cogs on a 10 or 11 speed cassette. Pushing out the chainline would relieve this problem a bit but it introduces problems of Q-factor. For this reason, I don't see even 2x12 catching on.
The case for 1xN is entirely different. In that case, the only limits are Q-factor and cross-chaining limits. Cross-chaining is really a matter of (1) the chainring's ability to retain the chain, (2) the cog's ability to retain the chain, and (3) the ability of the chain to tolerate the angle. The first issue is largely already solved with narrow-wide chainrings. The third issue is somewhat solved by modern chains, which are fairly flexible, and can probably be improved. The second issue is probably the limiter without some new technology. The 50T cogs appearing on some 12-speed cassettes are pretty huge and having a significant angle from the cog to the chainring has got to cause problems for a cog that is meant to release the chain smoothly on demand. I'd guess we're near that limit at 12-speed.
I predict that if we get 14-speed cassettes they're going to require a smaller pitch chain to reduce the size of the big cogs.
The "need" for more cogs is driven primarily by compact double and single ring cranksets. Selling a compact double to someone who really needs the low gearing of a triple requires a wide-range cassette. A wide range cassette enables a good marketing narrative for more cogs to achieve small gaps in the gearing. With a single ring crank wide gearing is even more necessary and so the push for more cogs is proportionately compelling.
Using a compact double with 50-34 chainrings, when the chain is on the small ring it will rub the big ring at around 2.3 degrees, which eliminates the two smallest cogs on a 10 or 11 speed cassette. Pushing out the chainline would relieve this problem a bit but it introduces problems of Q-factor. For this reason, I don't see even 2x12 catching on.
The case for 1xN is entirely different. In that case, the only limits are Q-factor and cross-chaining limits. Cross-chaining is really a matter of (1) the chainring's ability to retain the chain, (2) the cog's ability to retain the chain, and (3) the ability of the chain to tolerate the angle. The first issue is largely already solved with narrow-wide chainrings. The third issue is somewhat solved by modern chains, which are fairly flexible, and can probably be improved. The second issue is probably the limiter without some new technology. The 50T cogs appearing on some 12-speed cassettes are pretty huge and having a significant angle from the cog to the chainring has got to cause problems for a cog that is meant to release the chain smoothly on demand. I'd guess we're near that limit at 12-speed.
I predict that if we get 14-speed cassettes they're going to require a smaller pitch chain to reduce the size of the big cogs.
That may not be the case with the rear, as the dual pulley derailleur guides the chain onto the rear sprocket. Perhaps going back to a Suntour 3 pulley system to straighten the chain by the time it gets released from the rear derailleur. Pulling the chain off of the top of a spinning rear sprocket doesn't do much.
05-30-17, 12:43 PM
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05-30-17, 12:47 PM
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If someone REALLY wanted low Q and lots of gears, one could put the cassette outside the "dropout". Something like this, but do a two-sided rear triangle, make the seatstays and chainstays on the drive side very slender and have them follow the spokes inward to allow more room for the large cogs, and have the large cogs inbound from the bottom of the cassette body, like Sram ones are nowadays...
Perhaps one could design it to actually move the rear cassette right and left as one shifts. The spacing between rear sprockets would not have to be constant either. Give chain clearance for the sprocket being used, but collapse the rest. Shifting, however, would get complex.
05-30-17, 12:47 PM
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One can yank the chain off of the big ring in front due to an inadequate guide to keep the chain on the ring (without rubbing the derailleur).
That may not be the case with the rear, as the dual pulley derailleur guides the chain onto the rear sprocket. Perhaps going back to a Suntour 3 pulley system to straighten the chain by the time it gets released from the rear derailleur. Pulling the chain off of the top of a spinning rear sprocket doesn't do much.
That may not be the case with the rear, as the dual pulley derailleur guides the chain onto the rear sprocket. Perhaps going back to a Suntour 3 pulley system to straighten the chain by the time it gets released from the rear derailleur. Pulling the chain off of the top of a spinning rear sprocket doesn't do much.
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05-30-17, 12:48 PM
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While I agree that internally geared hubs and possibly CVTs are a natural future path, we are pretty far from the demise of the derailleur. To be light enough to be a viable alternative for anything but a city bike, the IGHs will have to shrink in size by 2/3rds and yet at the same time multiply in capabilities.
Just as cars are going to 8 and 10 speed automatic transmissions to maximize efficiency, so too will bicyclists seek more gears. It's all about the weight/benefit trade offs. These new automotive transmissions with many gears are massive; the trade off on a bike is much more focused on the transmission system weight vs. the drive efficiency of having just the right gear for every moment. For maximum performance, car transmissions use clutches instead of fluid couplers, hence the growth of dual clutch automanuals.
But cost and wear are a big issue on a bike; chains, cassettes and chainrings are all wear items that need fairly frequent replacement. For cars, rarely do any sort of clutches last more than 100k miles; not to mention an SMG/DCT hydraulic pump ($$$$$). That may seem a somewhat low mileage number for a car, but would be a massive number for a bike.
So for the IGH to really beat a derailleur set up, it will not only have to be equally light and offer a great gear range, but it will also have to last. Whatever advances are made in transmission technology, we are much more limited by metallurgy and the periodic table itself. Metal rubbing on metal or friction material causes wear. If an IGH does not last the life of a bike, it will need modestly priced wear parts.
To me, it seems the ideal set up of the future would completely eliminate any sort of gears at the rear, have all gearing built into the bottom bracket. And then have a either a belt driving the rear wheel, or a carbon fiber shaft drive.
Just as cars are going to 8 and 10 speed automatic transmissions to maximize efficiency, so too will bicyclists seek more gears. It's all about the weight/benefit trade offs. These new automotive transmissions with many gears are massive; the trade off on a bike is much more focused on the transmission system weight vs. the drive efficiency of having just the right gear for every moment. For maximum performance, car transmissions use clutches instead of fluid couplers, hence the growth of dual clutch automanuals.
But cost and wear are a big issue on a bike; chains, cassettes and chainrings are all wear items that need fairly frequent replacement. For cars, rarely do any sort of clutches last more than 100k miles; not to mention an SMG/DCT hydraulic pump ($$$$$). That may seem a somewhat low mileage number for a car, but would be a massive number for a bike.
So for the IGH to really beat a derailleur set up, it will not only have to be equally light and offer a great gear range, but it will also have to last. Whatever advances are made in transmission technology, we are much more limited by metallurgy and the periodic table itself. Metal rubbing on metal or friction material causes wear. If an IGH does not last the life of a bike, it will need modestly priced wear parts.
To me, it seems the ideal set up of the future would completely eliminate any sort of gears at the rear, have all gearing built into the bottom bracket. And then have a either a belt driving the rear wheel, or a carbon fiber shaft drive.
05-30-17, 12:49 PM
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Perhaps one could design it to actually move the rear cassette right and left as one shifts. The spacing between rear sprockets would not have to be constant either. Give chain clearance for the sprocket being used, but collapse the rest. Shifting, however, would get complex.
05-30-17, 01:39 PM
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I'll be one of them. I don't want my bike controlled by some new generation HAL 9000.
05-30-17, 01:41 PM
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The bike industry has been locked into a planned obsolescence path of adding another cog to the cassette ever 7 years - for decades.
At 9 cogs, we were already well past the point of diminishing returns. But with 11 cogs in the rear we are now at a point where rear wheels have so much dish and spoke tension differentials that there is no where left to go. I suppose the industry could increase rear stay spacing, but wider stays mess with chainlines and widen Q-factors. Current generation bikes with wide Q-factors are ridiculous to ride - it feels like being on a horse.
A 2 x 11 drivetrain provides all of the gear combinations that any rider could possibly use. For the industry to go to 12-speed cassettes would be seen as clearly absurd, even for the most gullible 'upgrader' or 'early adopter' that the industry loves and depends upon for sales churn.
This is why 1 x drivetrains are critical to the future of the industry. Eliminating the rings provides justification for adding even more gears in the rear. The sales pitch here is convincing relatively new riders that front shifting is too complex and confusing. This way, there is the justification to go to 1 x 12, 1 x 13 drivetrains, and beyond.
This could milk another decade or more of planned obsolescence timeline for the bike industry.
At 9 cogs, we were already well past the point of diminishing returns. But with 11 cogs in the rear we are now at a point where rear wheels have so much dish and spoke tension differentials that there is no where left to go. I suppose the industry could increase rear stay spacing, but wider stays mess with chainlines and widen Q-factors. Current generation bikes with wide Q-factors are ridiculous to ride - it feels like being on a horse.
A 2 x 11 drivetrain provides all of the gear combinations that any rider could possibly use. For the industry to go to 12-speed cassettes would be seen as clearly absurd, even for the most gullible 'upgrader' or 'early adopter' that the industry loves and depends upon for sales churn.
This is why 1 x drivetrains are critical to the future of the industry. Eliminating the rings provides justification for adding even more gears in the rear. The sales pitch here is convincing relatively new riders that front shifting is too complex and confusing. This way, there is the justification to go to 1 x 12, 1 x 13 drivetrains, and beyond.
This could milk another decade or more of planned obsolescence timeline for the bike industry.
05-30-17, 01:59 PM
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I'm stuck in the 3 x 9 camp (Ultegra) for road. Alfine 11 for the commuter bike though!
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05-30-17, 02:48 PM
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05-30-17, 02:52 PM
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fwiw and a a bit off topic, I see electronic shifting (and that enabling automatic shifting) moving into lower cost bikes more rapidly than most would think. I think that will also drive more 1xX setups?
why?
cost and simplicity. Electronic wireless will eliminate a lot of cabling, making bikes cheaper. going 1xX reduces cost by not having to have the front shifter mechanism, software and shift botton. Once electronic is common, it is not that big a deal to go automated
why?
cost and simplicity. Electronic wireless will eliminate a lot of cabling, making bikes cheaper. going 1xX reduces cost by not having to have the front shifter mechanism, software and shift botton. Once electronic is common, it is not that big a deal to go automated
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05-30-17, 02:56 PM
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05-30-17, 03:02 PM
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I was thinking today, there has to be a practical limit for the number of cogs for a rear wheel to have. Today, we have up to 12 speeds, but will that trend continue? 13? 14? 15? Expanded rear dropout spacing? Even if they expand the dropout spacing, the wheel dish gets to be so bad that it'd be impossible to build a long lasting wheel.
When do you think the cog "expansion" will stop? Or what do you think will enable the next "number of speeds" revolution? Hyper efficient IGH's combined with cassettes (like SRAM dual drive)? Or will it be the bottom bracket 2 speed cranksets?
When do you think the cog "expansion" will stop? Or what do you think will enable the next "number of speeds" revolution? Hyper efficient IGH's combined with cassettes (like SRAM dual drive)? Or will it be the bottom bracket 2 speed cranksets?
SRAM has been most likely to introduce 'clean slate' new designs but they've also been embarrassed by a ton of recalls and their gear generally grinds and clanks often a touch more slowly compared to shimano. They've also been great about keeping new designs under wraps as leaks seem to be extremely uncommon in the industry as a whole. Very few 'spy shots' to be found in industry rags.
In other words, there is very little information or clear pattern which would allow us to make reasonable guesses on what drivetrains will be available in the next 5-10 years.
What would I LIKE to ride? At least a 12 or even 13 speed cassette with two rings. Cassette options: 11-34 for 1:1 gear ratio for extreme climbs; at least 11-17 straight blocks. 3 up and 3 down shifts as standard for mech and electronic systems. Wireless electronic with 2X current battery capacity.
As far as auto shifting, I think it would be extremely cool. Let's pair it with motors! jk.
Eventually someone in marketing will have a huge ergonomic "breakthrough". Low Q-factors for many people are both faster and better for their knees. (Well, duh!) Chains have been moving right for the past few decades to stuff more and more gears onto the cluster. But our bodies will take a few thousand years to do the same adaptation. (Maybe longer, this doesn't affect our breeding ability and therefore genetics.) My knees love this bike!
Ben
Ben
You might use each cog a little less, slowing wear for the cassette as a whole meaning it would be a wash as far as replacement intervals. As far as 'width of bearing surface' couldn't this be kept as a constant while the width of the chain is reduced?
05-30-17, 03:06 PM
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fwiw and a a bit off topic, I see electronic shifting (and that enabling automatic shifting) moving into lower cost bikes more rapidly than most would think. I think that will also drive more 1xX setups?
why?
cost and simplicity. Electronic wireless will eliminate a lot of cabling, making bikes cheaper. going 1xX reduces cost by not having to have the front shifter mechanism, software and shift botton. Once electronic is common, it is not that big a deal to go automated
why?
cost and simplicity. Electronic wireless will eliminate a lot of cabling, making bikes cheaper. going 1xX reduces cost by not having to have the front shifter mechanism, software and shift botton. Once electronic is common, it is not that big a deal to go automated
The nice thing about the electronic shifting movement is that it lets me very easily identify the moment at which I became a retro-grouch. Not long ago, when I was happily upgrading to 10-speed and disc brakes I couldn't imagine myself becoming a retro-grouch. Now I see quite clearly that I am and always will be one.
Now if you'll excuse me, I need to go kick some kids off of my lawn.
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05-30-17, 03:10 PM
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All past 3x7 is far from objectively, technicaly worthy for those not racing.
However, marketing and sales are inventive. More gears, or "reinventing" singlespeed as a new hype - as long as new things are sold, incompatible with older stuff if possible.
However, marketing and sales are inventive. More gears, or "reinventing" singlespeed as a new hype - as long as new things are sold, incompatible with older stuff if possible.
05-30-17, 03:22 PM
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The nice thing about the electronic shifting movement is that it lets me very easily identify the moment at which I became a retro-grouch. Not long ago, when I was happily upgrading to 10-speed and disc brakes I couldn't imagine myself becoming a retro-grouch. Now I see quite clearly that I am and always will be one.
05-30-17, 04:16 PM
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shimano already has a patent for a 14sp. cassette. The inner plates on the chain are looped over the teeth of the cogs.
I hope my 7 and 8sp. setups outlast my old butt.
I hope my 7 and 8sp. setups outlast my old butt.
05-30-17, 06:06 PM
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Define "practical." For a mechanical engineer, what's practical is whatever he's paid to design. Everything else is just overhead. If someone had approached Tullio Campagnolo in 1950 and said, "I want you to build me a 10-speed rear derailleur, and here's a billion lire to get you started," he'd have had Campy's 20-sp gruppo on the market 40 years early.
As for automatic bicycle transmissions, they already came and (mostly) went. You guys must've blinked and missed them. Browning Smart Shift,
, AutoBike Smart Shift 2000, just to mention three.
Their universal problem -- apart from too much weight and too little reliability -- was that they couldn't know what size gear the rider wanted to be in at any given moment. Cyclists often change gears in advance of the change in conditions because they don't want to lose momentum (or foot speed) when the conditions do change. Even if they had been weightless (heck, even if they levitated) and were stone reliable, the auto-mixers still compelled you to ride in the gear-inches of their selection.
Cars don't care about losing something like "foot speed" because they don't get tired. All they have to do to get back on top of the gear is throw another dinosaur on the fire. A cyclist's legs, ...not so much.
But I think it's an answer to a question no one much is asking. Or cares about. If you have energy enough to ride a bicycle 10 miles (or even just two), is it really too taxing to occassionally have to throw the shift lever?
I keep praying that some 'interloper' like SRAM or FSA will drop out of the arms race and concentrate on making a high-end, ultra-light, ultra-durable 8 or 9-speed gruppo. Even a 10-speed, because it could have some stabilizing effect and restore some sanity to the market. Or it could be that the majority of cyclists are too gullible.
As for automatic bicycle transmissions, they already came and (mostly) went. You guys must've blinked and missed them. Browning Smart Shift,
Their universal problem -- apart from too much weight and too little reliability -- was that they couldn't know what size gear the rider wanted to be in at any given moment. Cyclists often change gears in advance of the change in conditions because they don't want to lose momentum (or foot speed) when the conditions do change. Even if they had been weightless (heck, even if they levitated) and were stone reliable, the auto-mixers still compelled you to ride in the gear-inches of their selection.
Cars don't care about losing something like "foot speed" because they don't get tired. All they have to do to get back on top of the gear is throw another dinosaur on the fire. A cyclist's legs, ...not so much.
But I think it's an answer to a question no one much is asking. Or cares about. If you have energy enough to ride a bicycle 10 miles (or even just two), is it really too taxing to occassionally have to throw the shift lever?
I keep praying that some 'interloper' like SRAM or FSA will drop out of the arms race and concentrate on making a high-end, ultra-light, ultra-durable 8 or 9-speed gruppo. Even a 10-speed, because it could have some stabilizing effect and restore some sanity to the market. Or it could be that the majority of cyclists are too gullible.
05-30-17, 08:04 PM
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As for automatic bicycle transmissions, they already came and (mostly) went. You guys must've blinked and missed them. Browning Smart Shift, Land Rider Auto Shift, AutoBike Smart Shift 2000, just to mention three.
Their universal problem -- apart from too much weight and too little reliability -- was that they couldn't know what size gear the rider wanted to be in at any given moment. Cyclists often change gears in advance of the change in conditions because they don't want to lose momentum (or foot speed) when the conditions do change. Even if they had been weightless (heck, even if they levitated) and were stone reliable, the auto-mixers still compelled you to ride in the gear-inches of their selection.
Their universal problem -- apart from too much weight and too little reliability -- was that they couldn't know what size gear the rider wanted to be in at any given moment. Cyclists often change gears in advance of the change in conditions because they don't want to lose momentum (or foot speed) when the conditions do change. Even if they had been weightless (heck, even if they levitated) and were stone reliable, the auto-mixers still compelled you to ride in the gear-inches of their selection.
05-30-17, 08:22 PM
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...
At 9 cogs, we were already well past the point of diminishing returns. But with 11 cogs in the rear we are now at a point where rear wheels have so much dish and spoke tension differentials that there is no where left to go. I suppose the industry could increase rear stay spacing, but wider stays mess with chainlines and widen Q-factors. Current generation bikes with wide Q-factors are ridiculous to ride - it feels like being on a horse.
...
At 9 cogs, we were already well past the point of diminishing returns. But with 11 cogs in the rear we are now at a point where rear wheels have so much dish and spoke tension differentials that there is no where left to go. I suppose the industry could increase rear stay spacing, but wider stays mess with chainlines and widen Q-factors. Current generation bikes with wide Q-factors are ridiculous to ride - it feels like being on a horse.
...
Ben
05-30-17, 09:13 PM
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Their universal problem -- apart from too much weight and too little reliability -- was that they couldn't know what size gear the rider wanted to be in at any given moment. Cyclists often change gears in advance of the change in conditions because they don't want to lose momentum (or foot speed) when the conditions do change. Even if they had been weightless (heck, even if they levitated) and were stone reliable, the auto-mixers still compelled you to ride in the gear-inches of their selection.
But riding until you're stupid is half the fun, ain't it?
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05-30-17, 09:48 PM
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With the above talk of IGH's being inefficient and heavy, I wonder if a hybrid IGH design might be the next innovation. If you could design a bottom bracket/crankset to have just two or three gears but use a single chainring, you could keep the simple rear derailleur shifting gears across a cassette. I could even see a design that moves the chainring slightly left and right while shifting gear ratios to keep the chainring aligned with the appropriate range, much like a double setup. It seems like making two gears up front reasonably efficient would be much easier than 8+ gears of many internal mech today. The chainring (wear-point) could mount to a carrier, so that it would be replaceable cheaply. Pair it all with either a mechanical or electronic R/D, and you'd have a pretty slick system.
-Jeremy
-Jeremy
05-30-17, 11:21 PM
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I like MTB-size shifts and I don't need a 6:1 range so that looks like 1x11 speed, or 2x9, or 3x7. I built my commuter as a 27 speed mainly because it was becoming harder to get premium 8 speed stuff, and I wanted to try a Shimergo build. (in the future I might replace the road triple with a mountain double, I barely use the top gears.) 27 speed has been around for 20 years now. The Deore/Tiagra/50 level stuff is acceptable. The premium stuff really is nicer. You can still get XT level 9-speed stuff... for now.
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Genesis 49:16-17
Genesis 49:16-17
Last edited by Darth Lefty; 05-30-17 at 11:25 PM.
05-30-17, 11:26 PM
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With the above talk of IGH's being inefficient and heavy, I wonder if a hybrid IGH design might be the next innovation. If you could design a bottom bracket/crankset to have just two or three gears but use a single chainring, you could keep the simple rear derailleur shifting gears across a cassette.