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Cadence range, cassette gaps and efficiency

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Cadence range, cassette gaps and efficiency

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Old 08-12-18, 06:09 PM
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Ericoschmitt
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Cadence range, cassette gaps and efficiency

I've been googling on it, but couldn't find an answer yet (a controlled study), so let's see what you think:

How much more efficient is a close ratio cassette compared to a wide range one in a flatter course?

This new 1x wave makes me think about this often.

For example, a 12-25 cassette vs. an 11-42, considering you are riding between the 13-19t cogs, same chainring, bike, and speed range.
So the 12-25 has 1 tooth jumps, and the 11-42 has 2 tooth jumps. We have all been there: riding the flats with a cassette that has no 16t cog, the 17t is too light, 15t is too hard (same thing in a cassette that has no 12, 14, or 18t such as the 11-42 at other speeds).
So how much energy is being wasted for not being on the desired cog?
Should we bother having different cassettes to choose from, or just use the biggest one we ever need for every ride?

The gap between a 15t and a 17t is 13.3%, so if you are riding 15t at 90rpm and shift to 17t you are suddenly at 102rpm. If you had a 16t, that is a 6.6% gap and the same shift gives you a cadence of 96rpm, which is a much nicer gap IMO. These cadence numbers are just to illustrate, I'm not talking about the absolute number, but the gap in the shifts. Do small shifts give us a big benefit? Racers loved corncob cassettes in the past! Where has that love gone?

I see many riders moving to 1x, and getting a wide range cassette that matches the range theiy had before with 2x, as if the bigger gaps made no difference for them. And then some people do that for a TT bike with an 11-28 or 11-32, where I suppose efficient cadence makes the most difference. On the other hand, taking off the front der. and one of the chainrings saves a few watts in aerodynamics, could that offset the cadence efficiency for a TT setup?

In my experience, big gaps are annoying when the gradient or wind changes slowly, and I get very upset in those times when one gear is too hard and the other is too easy. That happens with my older 2x10 bike which is setup with 50/34x12-36, and I do use that low gear for some serious hills around here. In this case, for this bike, although I hate the gaps, I hate climbing at 50rpm even more, so I took the 12-25 cassette off and put this 12-36 in place with a MTB der. But other than getting upset by the big gaps, and "feeling" it might not be the best cadence, I wonder if that "wrong" cadence actually steels me some watts. Usually the first gap that I find tolerable is 17-19, but even then I miss the 18t cog sometimes. This feeling is paradoxical, because I also ride a fixie very often (49x17), with widely varied cadences, but in this case, when I don't have gears at all, I seem to switch off the cadence sensor in my brain and just ride the bike, my legs go CVT! Still it pisses me off when I do shift a gear and the gap is too big...

What makes me waste neurons with this topic is that I'm thinking about a dedicated TT bike in the future, and for this use 1x does have an appeal, since TT (and triathlon, who knows what I might want in the future) courses are often flatter and/or shorter, so even if I have to do a short climb standing up, I might get that energy back from a small aero benefit over a longer time. Another reason for doing so is that I really want to experiment with shorter cranks, and I can find 135mm BMX cranks with 110bcd spider on ebay, but those will only accept one chainring unless I adapt the spider. Shorter cranks also help staying aero without loosing power. So all that makes me think about going 1x for a TT bike, using cassettes from 12-25 to 12-29 (campy). Any course requiring lighter gears, I'd do what I do nowadays, and put clips on my road bike.

For other applications such as road or gravel, I'm still a triple lover with 3x11, but q-factor also comes into play, and then that's a q-factor vs. gearing gaps discussion, possibly better left for another topic
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Old 08-12-18, 06:14 PM
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asgelle
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Originally Posted by Ericoschmitt View Post
How much more efficient is a close ratio cassette compared to a wide range one in a flatter course?
What do you mean by efficiency? Work done per energy consumed? If so, there are plenty of studies on effect of cadence on efficiency. How gearing affects cadence would depend on terrain. In the extreme example of a road with constant grade, if one of the available gears matches the riders most efficient cadence, it wouldn't matter what the other gears were.
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Old 08-12-18, 06:27 PM
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I think that you're barking up the wrong tree when you use the 'efficiency," but I know what you're talking about. I don't think that it matters quite as much for those that aren't riding at the edge of their limits, but when you're just barely holding on to an effort, like trying not to get dropped or doing a tough interval, a cassette gap in the wrong place can mean spinning at a pace that you can't quite maintain or pushing with force that you can't quite maintain. It can be frustrating. This spring, I swapped over to a 12-25 11-speed cassette (1-tooth steps from the 12 to 19) on the road bike and I think it's awesome.
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Old 08-12-18, 06:28 PM
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Originally Posted by WhyFi View Post
... but when you're just barely holding on to an effort, like trying not to get dropped or doing a tough interval, a cassette gap in the wrong place can mean spinning at a pace that you can't quite maintain or pushing with force that you can't quite maintain.
The word for that is fatigue, not efficiency.
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Old 08-12-18, 06:30 PM
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Another conversation that is related; does efficiency equal high speed? Is there are trade off between the two, less efficient but slightly faster?
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Old 08-12-18, 06:36 PM
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Originally Posted by asgelle View Post
The word for that is fatigue, not efficiency.
I didn't say that the word was "efficiency."
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Old 08-12-18, 06:39 PM
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Originally Posted by colnago62 View Post
Another conversation that is related; does efficiency equal high speed? Is there are trade off between the two, less efficient but slightly faster?
It could be, but then the rider would fatigue sooner.

In fact, given how drag works, I could argue that slower is more efficient since you cover more distance per unit energy expended. It just takes longer to get there.
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Old 08-12-18, 06:54 PM
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I have two bikes: 50/34 11-speed double with a PG1170 11-28, and a Rival 1X with a 42T and an 11-speed XG1150 10-42.

The 11-28:
11-12-13-14-15-16-17-19-22-25-28

The 10-42:
10-12-14-16-18-21-24-28-32-36-42

The only shift where I "feel" the gap is that first 3-tooth jump on the 11-28, from 19 to 22. In a perfect world, that cassette would go 16-18-20-22, instead of having just a single, solitary, 2-tooth step.

I've honestly never once been bothered by the cog spacing on the 10-42.
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Old 08-12-18, 08:46 PM
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Originally Posted by DrIsotope View Post
I have two bikes: 50/34 11-speed double with a PG1170 11-28, and a Rival 1X with a 42T and an 11-speed XG1150 10-42.

The 11-28:
11-12-13-14-15-16-17-19-22-25-28

The 10-42:
10-12-14-16-18-21-24-28-32-36-42

The only shift where I "feel" the gap is that first 3-tooth jump on the 11-28, from 19 to 22. In a perfect world, that cassette would go 16-18-20-22, instead of having just a single, solitary, 2-tooth step.

I've honestly never once been bothered by the cog spacing on the 10-42.
Funny that you notice a 3t gap between 19-22 but don't mind a (bigger) gap 18-21 in the other cassette. It might be a mindset thing, that on the 1x you just don't care, while on the other you have just came from a series of 1t shifts. 19-21-24-28 would be better for that cassette really.
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Old 08-12-18, 08:56 PM
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Originally Posted by asgelle View Post
What do you mean by efficiency? Work done per energy consumed? If so, there are plenty of studies on effect of cadence on efficiency. How gearing affects cadence would depend on terrain. In the extreme example of a road with constant grade, if one of the available gears matches the riders most efficient cadence, it wouldn't matter what the other gears were.
I'm aware of studies like this:
https://www.researchgate.net/publica...during_cycling

They compare things like 60 vs 90 vs 120 rpm.
I know already my preferred cadence ranges, the range where I can put more power, the range I can sustain on long rides, and it happens to match what that study says.

But that and other studies don't explore what's the difference in a 1 hour effort between cadence varying 90-96rpm vs. 90-102 rpm. I don't know either. I just feel that, after you know what cadence you want for the effort you are doing, the less variation the better. But how much time do you loose in a flatish TT if you ride it with a cassette without the even numbered cogs? Is that meaningful at all in a TT or just a matter of preference? A TT bike usually gets ridden in 5-40km efforts, so that's the time frame I would want it to work the best, at my maximum effort level.

If a wider cadence range is acceptable, not impacting performance significantly, why should I bother running a FD at all? I certainly can adapt to ride at more varied cadence, as I have with that 12-36 10s cassette, but I wouldn't want to do that if it impacts performance negatively. On the other hand, if it's only a matter of making me upset, I'd be ok with those bigger gaps. Often our legs tell lies, so my feeling that big gaps suck could actually mean nothing performance-wise.

Well, I've read opinions on NuVinci CVT hubs, specially the electronic automatic one, that even though that hub adds drag compared to a der. system, the fact you are always exactly on the desired cadence makes up for the difference, so that gives food for thought.

Last edited by Ericoschmitt; 08-12-18 at 09:06 PM.
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Old 08-12-18, 09:09 PM
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I think someone else nailed it - if you're riding at the edge of your capability (e.g., just barely holding on a pace line), you can have issues with a wide-range/big-gap cassette that hurt your ability to hold a fixed speed. If you're by yourself or not racing, you typically just ride a bit slower, but if you're racing or riding in a group, this may have negative consequences. I ride 1x on my primary road bike, and I honestly have never has any issues with the gaps (or the fact my top speed is slightly curtailed), but I don't race and don't ride very often in groups. And I love single-lever shifting so the tradeoff to me is heavily in favor of 1x.

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Old 08-12-18, 09:13 PM
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Just do a range of FTP tests. 80, 85, 90, 95, 100rpm. See what works for you.
If 90 rpm is my optimum and it only varies 1% from that at 85 and 95, it doesn't mean it will be the same for you.
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Old 08-12-18, 09:19 PM
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Originally Posted by Dean V View Post
Just do a range of FTP tests. 80, 85, 90, 95, 100rpm. See what works for you.
If 90 rpm is my optimum and it only varies 1% from that at 85 and 95, it doesn't mean it will be the same for you.
I guess that's the smartest thing to do. A friend of mine has an smart trainer that I can use for that test.

But I think I'd have to do several mixed runs so that fatigue doesn't come into play, and repeat after a few days. Like intervals at 90, 96, 90, 96, 90, 96 with max effort, then another day the same but with 90 and 102 so I have 90 for control. Or something like that. And then compare watts.
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Old 08-12-18, 09:22 PM
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What gear range do you actually need? 1x may not be as bad as you think.
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Old 08-12-18, 10:09 PM
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Originally Posted by Racing Dan View Post
What gear range do you actually need? 1x may not be as bad as you think.

Old road bike: 2x10 50/34x12-36 originally it was 53/39x12-25, climbing was hard.

New road bike: 3x11 52/39/30x12-29 or 11-25 (training/climb or race/flat)

Gravel bike (drop bar mtb): 3x10 46/34/24 x 12-36 or 12/27 (hills/loaded, or flatter/unloaded) but with 60mm tires, makes gearing 9% heavier

Fixie road bike: 49x17 fixed most of the time, but I have 16 and 18 too. I can climb some of the hills with it too, but that involves lots of pain.


I do use gears that low, and I have spent lots of time looking at gearing charts at bikecalc. On the new road bike I'd get a smaller granny to live with only one cassette, but smaller BCD is 94mm, so I'd need a new crankset for that.

I'm about 61kg, ftp some 280w. Not that weak, but there are some steep hills that I enjoy climbing with at least 80rpm with the road bikes

To match those ranges with 1x I'd probably have to ride with a 11-50 cassette (mind the gap).


But on a TT bike, and flatter courses, I might be fine with 46~ x12-29.

I wouldn't want to use a TT bike for climbing steep hills anyway.


If I could know for sure that bigger gaps wouldn't make me slower, I'd be ok with 1x on the road really, especially because it lets me get q-factor narrower, and mess with oval chainrings, shorter cranks, etc.

I guess I'll have to test myself on a smart trainer to compare. I might as well need a decent test protocol for that.

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Old 08-12-18, 10:18 PM
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Even on casual group rides I don't mind the larger gaps on my 1x10. Granted, I am running a 44t with a 11-36 and not a 11-42.
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Old 08-12-18, 11:12 PM
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You've got some 3 tooth gaps on one setup,

but the gaps on the fixed gear are.... infinite.
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Old 08-13-18, 12:02 AM
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Originally Posted by Ericoschmitt View Post
I guess that's the smartest thing to do. A friend of mine has an smart trainer that I can use for that test.
Have you tried to find your optimal crank torque, too? If not, why not?
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Old 08-13-18, 01:46 AM
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The trouble with things like these is that humans are tricky as measuring devices. We can be quite good at noticing relative differences, but appallingly sucky at quantifying absolute values.
And a rider that FEEL that the bike is just ”right” may simply ride a little harder and become a little faster because of that. The actual difference in performance or efficiency may be minimal to insignificant. Rider contentedness, ”placebo” brings the improvement, not the actual, mechanical difference.
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Old 08-13-18, 10:42 AM
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Originally Posted by Dean V View Post
Just do a range of FTP tests. 80, 85, 90, 95, 100rpm. See what works for you.
If 90 rpm is my optimum and it only varies 1% from that at 85 and 95, it doesn't mean it will be the same for you.
How does this even work...you'd need at least 1 recovery day between an FTP test so you are spending like a week doing FTP tests? You'd likely accumulate enough TSS and a poor TSB by then such that it would no longer be representative of your true FTP either so then you'd need to repeat in a different order after a week off?
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Old 08-13-18, 11:26 AM
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I have never seen anything very convincing that smaller gear increments (the range divided by 7 as opposed to 10 for instance) is inherently more efficient. I see a lot of evidence that road cyclists generally prefer more gears. It indicates, to me, that the preference is due to something other than efficiency (even though many of them will express it that way).
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Old 08-13-18, 11:36 AM
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The whole problem of wide spacing is overstated.

At a minimum, one adapts. Adapt means better able to push big gears and spin smaller gears. Your range of usable cadence will be wider out of simple necessity. You will be a more versatile rider.

There are times where a tightly spaced gears makes sense and it takes some time to get used to wider spacing but switching back and forth between a wide spaced gravel bike and a narrower road bike for example, will make you a better, faster rider.


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Old 08-13-18, 11:43 AM
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Originally Posted by wphamilton View Post
I have never seen anything very convincing that smaller gear increments (the range divided by 7 as opposed to 10 for instance) is inherently more efficient. I see a lot of evidence that road cyclists generally prefer more gears. It indicates, to me, that the preference is due to something other than efficiency (even though many of them will express it that way).
Maybe you can explain why we see pros and other top cyclists using 11-23t cassettes in crits/TTs?
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Old 08-13-18, 12:23 PM
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Originally Posted by noodle soup View Post
Maybe you can explain why we see pros and other top cyclists using 11-23t cassettes in crits/TTs?
Speaking to the Rally mechanic, I was told they keep their 11-28 (or 30) on all the time, and these riders have mechanics to change cassettes for them through no effort of their own.
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Old 08-13-18, 12:32 PM
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If a rider gets to pick their speed (like on a solo ride) then fewer gears shouldn't decrease efficiency. But if a rider doesn't pick their speed (like on a group ride) there will be speeds that are less efficient than others. More gear options increases the chance that the rider can find a more efficient gear for any given speed.
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