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Data on SS efficiency vs geared

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Data on SS efficiency vs geared

Old 05-18-22, 08:16 PM
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steeltrap21
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Data on SS efficiency vs geared

I am surprised that I have not been able to find any actual data on the efficiency of single speed vs geared. I generally ride road geared, but occasionally train with SS. I have a geared bike and a SS bike set up very similarly. My intent is to ride them alternating laps over a 7.5 mile course near my home. I will also have some laps with the geared bike in one gear the same ratio as the SS. I realize the results will be somewhat specific to me, the course, etc., but I will find them interesting.

I see lots of speculation but no data. If any one has or knows of actual data, please let me know.
Thanks, Steeltrap21
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Old 05-19-22, 09:15 AM
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Originally Posted by steeltrap21 View Post
I have a geared bike and a SS bike set up very similarly. My intent is to ride them alternating laps over a 7.5 mile course near my home. I will also have some laps with the geared bike in one gear the same ratio as the SS. I realize the results will be somewhat specific to me, the course, etc.,
What "results" will you be comparing, besides lap times?
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Old 05-19-22, 09:33 AM
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https://www.cyclingabout.com/drivetr...between-1x-2x/

https://probikeplanet.com/are-single...n-other-bikes/
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Old 05-19-22, 09:45 AM
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Average speed, average heart rate.
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Old 05-19-22, 09:57 AM
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Thanks prj71, I have seen both links. Neither one provides actual data on single speed vs geared. Intuitively, I would think single speed is more efficient mechanically, but is there a significant difference? I think we are pitting the efficiency of the human body at a reasonable cadence (geared) against the mechanical efficiency of SS. Of course, in hilly terrain and strong winds, I would think geared always wins. On flatter courses and light wind, the SS might win. I am interested because I sometimes go with a nearby informal race that is relatively flat. I am 75 and need all the help I can get (at least 20 years older than anyone else out there), so if SS would give me 2% or so that could be significant. Similarly for a time trialist.
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Old 05-19-22, 10:26 AM
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In the articles conclusion:
When the chainline is almost straight, the drive efficiency is within 1-watt between 1X and 2X drivetrains, resulting in the 1X drivetrain being 0.2% slower. This translates to a 25 second time penalty over 100km if using the 1X drivetrain.


A perfectly straight chainline is the same configuration as ideal single-speed.

There is just so many factors to keeping up with the young'uns that losses from a straight chainline at a power most enthusjastic cyclists aspire to reach are insignificant. Ĺ second per mile. Really?

How does your leg muscles make power? Nutrition, fitness, fatigue? Are your chain rings round or oval? What kind of oval? How round is your pedal stroke? What is your cadence? what diameter is your rings/cogs to get the same ratio? Did you wear your tight fitting jersey today? Aero much? Are you aero? (& by that I mean: Not shaped like a barrel, are you?) Is your bike equipped with TT bars? Do you use them? Are you practised/acclimatized enough to turn good power while in them? To put it on perspective: Urban legend has it that a single inch of exposed cable housing is about a watt at 25mph. How's your rolling resistance? Any of these thing can combine to be 30, 40, 60 watts or more difference at 25mph.

You can chase all of these things. In the end a single watt of drivetrain is not the reason the kids are faster.

Last edited by base2; 05-19-22 at 10:49 AM.
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Old 05-19-22, 10:43 AM
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Originally Posted by steeltrap21 View Post
Thanks prj71, I have seen both links. Neither one provides actual data on single speed vs geared. Intuitively, I would think single speed is more efficient mechanically, but is there a significant difference? I think we are pitting the efficiency of the human body at a reasonable cadence (geared) against the mechanical efficiency of SS. Of course, in hilly terrain and strong winds, I would think geared always wins. On flatter courses and light wind, the SS might win. I am interested because I sometimes go with a nearby informal race that is relatively flat. I am 75 and need all the help I can get (at least 20 years older than anyone else out there), so if SS would give me 2% or so that could be significant. Similarly for a time trialist.
I think the answer is difficult to determine because efficiently depends on many factors including the lube used on the chain, the actual interaction of the cog and roller in the chain, and the ratio of the gears. Here is an article that details the difference between geared hubs and derailleurs but also outlines some challenges to measuring small differences in efficiency: https://www.whpva.org/HParchive/hp55p11-15.pdf

There is also “Effects of Frictional Losses on Bicycle Chain Drive Efficiency” by Spicer et.al. (You can use a search to find a full pdf copy of the paper) that is also interesting. All things being equal bigger cogs in the back are more efficient than smaller ones by a larger amount then I would have guessed so it pays to have your favorite gear in a straight line and set up the gearing so this is a largish cog. So if your favorite gear is 46-15 switching to 50-16 would be slightly more efficient by about a 1%. Also if you favorite gear results in a lot of chain deflection consider a cassette that would have a straight chain line.
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Old 05-19-22, 12:51 PM
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For solo rides on our modest terrain (flats and modest hills) I donít see a lot of net difference in terms of average speed between SS and geared.

Mechanical efficiency differences are probably a few watts. A bigger difference will be differences in cadence. Formenti at Kingís College has published a couple of papers in the last decade documenting the internal work we do cycling as a function of cadence. This is the work we do moving our legs, feet and the cranks and pedals around in a circle. Think of it as the overhead we have to do to keep the feet in a position to push the pedals.

Itís a sharply increasing function of cadence and reaches 1 Watt per kg (of rider mass) at 110 rpm.

So on a hill climb, SS is likely to make you a bit more efficient at a lower cadence but at the cost of much higher pedal force and muscle strain.

Conversely, if you spin super fast to go a bit faster downhill or to keep up in a pace group, SS will make you less efficient than a similar geared rider able to hold that speed with a reasonable cadence.

If you are trying to keep up with geared riders, you should probably have gears, too. For solo, rides, it makes less difference than youíd think.

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Old 05-19-22, 03:05 PM
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There will be a slight difference in drag, maybe a watt or 2, depending on how many jockey wheels the SS bike uses and assuming you don't mean fixed, you mean freewheel but only one gear. It also makes a huge difference what your local terrain is and therefore how many g.i. you use on the SS. SS and fixed are usually geared as a compromise between flat and hills. Normally the geared bike will be much faster on the flat. I rode SS with a geared bike group many years ago. I could sit in at 130 cadence, but could only pull at 105, though I could have taken short pulls at the 130 cadence speed with my geared bike at a 90 cadence. Cadence eats HR unless you're LA. OTOH, if you only ride on the flat and thus would use the same g.i. SS or geared, then very small difference, like <1%.
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Old 05-20-22, 03:36 AM
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Originally Posted by billridesbikes View Post
All things being equal bigger cogs in the back are more efficient than smaller ones by a larger amount then I would have guessed so it pays to have your favorite gear in a straight line and set up the gearing so this is a largish cog. So if your favorite gear is 46-15 switching to 50-16 would be slightly more efficient by about a 1%.
This sounds questionable because given the same gear ratio on the same bike, the angles between the chain/sprocket tangent points are the same, resulting in the sum of the angles subtended by the links to be the same regardless of sprocket size (ratio held constant) - basically big sprockets mean more links at less angle and small sprockets mean less links at more angle.
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Old 05-20-22, 11:10 AM
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Originally Posted by son_of_clyde View Post
This sounds questionable because given the same gear ratio on the same bike, the angles between the chain/sprocket tangent points are the same, resulting in the sum of the angles subtended by the links to be the same regardless of sprocket size (ratio held constant) - basically big sprockets mean more links at less angle and small sprockets mean less links at more angle.
I think all the work is done by the 2 or 3 links about to come off the sprocket regardless of size, making the bigger sprocket more efficient.

I also think it isnít enough for most people to consider without the power changing directions like in a car rear end.
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Old 05-22-22, 05:18 PM
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They are way more efficient!
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Old 05-23-22, 11:50 AM
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While not data, Sheldon Brown makes some very good points in favor of single speed efficiency...

Why ride a Singlespeed?

Modern multi-speed bikes are marvels of technology, and allow a cyclist to select the gear ratio that will make the most efficient use of his/her energy. If you want to get the maximum possible speed/distance for the minimum effort (and there's nothing wrong with that!) you need a multi-speed bike...but, efficiency isn't everything!

If you're riding for sheer pleasure, or for exercise, you don't necessarily place that high a premium on output results, as measured in speed, distance or vertical climb. Instead, you may care more about the actual experience of riding your bike. In this case, you may be a candidate for a singlespeed bike.

Riding a singlespeed can help bring back the unfettered joy you experienced riding your bike as a child. You don't realize how much mental energy you devote to shifting until you relinquish your derailers, and discover that a whole corner of your brain that was formerly wondering when to shift is now free to enjoy your surroundings and sensations.

Paradoxically, a singlespeed is, in another sense, more efficient than a multispeed bike! While the single gear ratio will not be the "perfect" gear ratio for all conditions, in the conditions which fit the single gear, it is considerably more efficient mechanically than the drivetrain of a derailer bike.

A singlespeed bike dispenses with the weight of the derailers, shifters, cables, extra sprockets and longer chain. In addition, a singlespeed gear train runs the chain in a perfectly straight line from sprocket to chainwheel, and avoids the serpentine wind through the pulleys of a derailer. You can really feel the difference! A singlespeed is noticeably quicker and easier to pedal than a multispeed bike in the same gain ratio.

Singlespeed bikes are also considerably more sturdy and reliable than multispeed bikes. There's no derailer to bash if the bike falls over, catch on the underbrush or get overshifted into the spokes. The rear wheel itself is a lot stronger than one made with off-center (dished) spoking to make room for a whole bunch of sprockets on one side.
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Old 05-24-22, 10:48 AM
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Thanks for all of your comments. I am setting up two bikes with exactly the same configuration. The drive train for both bikes is clean, new, and well lubricated. One is geared, has derailleurs, but will always be in the 53/19 gear. The other bike will be single speed 53/19, no jockey wheels or derailleur. I will ride the bikes alternatingly over the 7.4 mile course for a month or so. This addresses the question of how much of a difference in mechanical efficiency there is between the two.

I understand that this still does not address the question of human efficiency on the two set ups, but at least it looks at one factor.
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Old 05-24-22, 09:52 PM
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I ran across this in a cyclingabout article: "Friction Facts have tested a singlespeed chain to be about 99% efficient at 150 watts (2-watts drag).... " Elsewhere, I think in one of the articles cited above, a graph by Ceramic Bearing, showed Dura Ace to be about 96.5% efficient at 150 watts. So this would imply that SS is about 2.5%, or about 4 watts better than Dura Ace. Doesn't sound like much and I am sure if the cadence goes very high or very low any gain in efficiency for the SS is quickly lost. Elsewhere I have read that a derailleur drivetrain can have efficiency as low as 88%. That would definitely make a difference.
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Old 05-25-22, 06:48 AM
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Do you have the same position and same tires/tubes on each bike? That could be much more impactful
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Old 05-25-22, 08:18 AM
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Originally Posted by steeltrap21 View Post
I see lots of speculation but no data.
You'll find lots of that in cycling. Collecting good data can be hard, time-consuming, and expensive, so much of what we know is due to trial and error.

"You manage what you measure", and too often, we've been satisfied by simple models of cycling mechanics based on what's easiest to measure. So a test jig will lead you to think that a single-speed bike with the skinniest high-pressure tires will be the most efficient and fastest. But is it really?
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Old 05-25-22, 09:36 AM
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To TMonk, yes same tires/tubes, wheels, bikes, geometry.
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Old 05-26-22, 02:15 PM
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I think I have a better way to address this. I have a Stages power meter which measures watts at the crank and an old Compu-trainer (if I can find all the pieces) that imposes load at the wheel. I could calibrate the two with the single speed at 150 watts per the Stages, and then see how much (if any) additional power is required for the geared.
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Old 05-26-22, 02:31 PM
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Originally Posted by steeltrap21 View Post
I think I have a better way to address this. I have a Stages power meter which measures watts at the crank and an old Compu-trainer (if I can find all the pieces) that imposes load at the wheel. I could calibrate the two with the single speed at 150 watts per the Stages, and then see how much (if any) additional power is required for the geared.
If this is something which you are really passionate about, why not do your own trials? The fact that there is little concrete data may be that it is intuitively determined that all things being equal, not having all of the "extras" a geared bike requires will result in more efficiency.

Frames can be made to be equal but once you introduce all of the components required for geared set-ups, you begin to add a lot of weight. The shifters, the cables, the derailers, the extra cogs, etc. Even if you were to use an IGH there is still a significant weight penalty.
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Old 06-02-22, 06:57 PM
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Originally Posted by son_of_clyde View Post
This sounds questionable because given the same gear ratio on the same bike, the angles between the chain/sprocket tangent points are the same, resulting in the sum of the angles subtended by the links to be the same regardless of sprocket size (ratio held constant) - basically big sprockets mean more links at less angle and small sprockets mean less links at more angle.
Was just thinking about this again - smaller sprockets (given same ratio) leads to higher chain tension which leads to higher friction, which results in bigger sprockets indeed being more efficient (at steady state anyway).
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Old 06-03-22, 09:07 PM
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SS vs Geared

I regularly ride several hilly road routes with very few flat areas. I ride with one of three single speeds or 4 geared bikes. The single speeds all have a little different gearing, chosen especially for my routes. For all rides, I try and keep my heart rate mostly in Zone 3 with some Zone 4 at the top of the hills. My HR efforts are fairly consistent as per my Polar watch. My average speeds are amazingly close with the extreme ranges within about 10% over the last 50 rides. Without doing a bunch of data analysis, the geared bikes might have a little advantage. I was surprised the SSs performed so well. Since they don't seem to have much if any penalty, I ride them a lot. There's something enticing about riding a SS. --Fred
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