There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
How fast will the OP be at 210 watts in his new aero gear???
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
Yes that’s the reason why you can’t determine the exact number watts saved if you ride a distance with a certain average speed (the drag is not linear with the speed).
Mind also that there is wind, so riding 36 km/h in in the above example with a head wind of 24 km/h will give you in fact those 27 watts calculated for 60 km/h.
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
How fast will the OP be at 210 watts in his new aero gear???
This is an example of what some riders like to use to quantify aero gains. Scroll down to the bottom. It converts CDA gains to an actual time and watt saving at a given race speed. In this case rider does HIM at 280w. I calculates a time for a flat course (no wind), and the a a new time for every test we did. So this guy found 23watt, almost 4min. It can be applied to a specific course and wind condition (Kona for example)
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
Yes that’s the reason why you can’t determine the exact number watts saved if you ride a distance with a certain average speed (the drag is not linear with the speed).
Mind also that there is wind, so riding 36 km/h in in the above example with a head wind of 24 km/h will give you in fact those 27 watts calculated for 60 km/h.
Not quite, quick back of napkin says 17W since power is also dependent on ground speed, not just air speed.
Also, going 36 km/h into 24 km/h headwind requires approximately same amount of power as going 51 km/h with no wind so not something people are that likely to experience very often in a triathlon.
ive been having some issues with understanding this too. rather, ive been having issues with the way the industry presents aero gains.
i have given up entirely on believing “wattage saved” claims. i think its complete BS to throw out one number (or even a range of number) of watts and claim that that will be what every rider would save. that is what brands do and i think its terrible. wind tunnel testing is very particular and quirky. very few riders read white papers. marketing departments get their hands on this stuff and make all the claims that we see, and deliberatly shroud important details of the testing. Rider on, rider off, speeds, yaw, baseline protocols.
speed of a rider is one factor, yes, but so is the power they ride at and the type of riding they do. and the notorious thing of how helmets are very particular for different people. for instance, take someone who averages 150w for an ironman bike split in “normal” kit on a decent stock tri bike. if they get an aero helmet (claimed by some to be 15ish?), shave their legs (10), get silca socks (8), upgrade stock tires (lets say it came with vittoria NEXTs, per BRR.com switching to GP5000 S TR would be 3 per tire, so 6 total)…you think they could do the exact same bike split at 38 less watts? hell no. you could expand this list of upgrades and if all wattage claims are to be believed, you could just endlessly add watts and probably get down to close to zero watts required! But marketing departments dont like that stuff.
savings should stop being presented in wattages. I’m not an aero nerd to know a better solution, but it should be more open. percentage of power produced along with percentage of CDA? i bought silca’s aero socks with the 4 to 8 watt claimed savings, and sorry to pick on silca because everyone does this, but there’s no F’in way those little ribs save 8 watts. maybe during a world tour sprint, at 60kph…but again it isn’t advertised that way. sorry to pick on silca but receiving those socks and seeing how unremarkable they were really sparked my displeasure with the way the industry presents this stuff.
I’m not an aero nerd to know a better solution, but it should be more open. percentage of power produced along with percentage of CDA?
i bought silca’s aero socks with the 4 to 8 watt claimed savings, and sorry to pick on silca because everyone does this, but there’s no F’in way those little ribs save 8 watts. maybe during a world tour sprint, at 60kph…but again it isn’t advertised that way. sorry to pick on silca but receiving those socks and seeing how unremarkable they were really sparked my displeasure with the way the industry presents this stuff.Agree your first sentence (quoted above) but it’s a communication challenge.
As for your silca socks rant, how do you know they don’t save you 4-8 watts? You’re a self-proclaimed ‘aero non-nerd’.
Because it’s just a sock. Albeit, a nice quality one. But The ribs dont even stick out. If I’m alone on this one I’ll shut up but I just don’t see a way, physically, that those socks are saving 8 watts compared to other socks, or a shaved leg at “casual” riding speeds. 8 watts (again, what speeds are we talking about? No one knows!) is a massive amount for one piece of equipment.
If I had to guess, the number of 8 saved is for sprinting speeds. Which goes to say, while silcas figure might be true for a very specific point in time for a specific rider, they aren’t saving ME 8 watts, cruising along at 170 during my 70.3.
savings should stop being presented in wattages. I’m not an aero nerd to know a better solution, but it should be more open. percentage of power produced along with percentage of CDA?
when you talk CDA, 1/3 of the people know what it is, 1/3 have heard of it, 1/3 don’t have a clue. Quote 0.236 and they are all lost. They just don’t get it. It’s a meaningless number for most.
% of total drag ? They can’t quantify what their drag is. 5% of something I can’t relate to means nothing
This is why we ask the rider “what power would you do a HIM at ?”. From that we calculate a finish time based on his baseline CDA. Then we calculate how many minutes (or seconds) a rider would save or how many watts you could preserve at get the same time as his original config. There is an article that will be published in the next month that gives examples for a typical AGer.
Our calculations are done on a flat course but can do it specific to any course they want. Of course there are other variables like barometric pressure…
One woman pro wanted to know “at xxx watts can I do Nice in y:00hours and/or can we get there on xxx watts”.
A very large percentage of people do not see all their aero gains reflected in race results. This is why I believe you should confirm optimizations in test riders, if you can.
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
Yes that’s the reason why you can’t determine the exact number watts saved if you ride a distance with a certain average speed (the drag is not linear with the speed).
Mind also that there is wind, so riding 36 km/h in in the above example with a head wind of 24 km/h will give you in fact those 27 watts calculated for 60 km/h.
Not quite, quick back of napkin says 17W since power is also dependent on ground speed, not just air speed.
Also, going 36 km/h into 24 km/h headwind requires approximately same amount of power as going 51 km/h with no wind so not something people are that likely to experience very often in a triathlon.
Thanks for the correction of my assertion: one never stops learning.
Isn’t that related to the grain of salt we should consider when looking at windtunnel results? If you ride without wind outside you have a relative speed with the air also nearby the ground equal to your speed, but if you’re in the windtunnel with a certain windspeed, this windspeed gets smaller and upto nill when measuring from a certain hight going down to the ground. I know that there are windtunnels with moving ground, but I think only very expensive ones for cars.
One thing with actual testing is getting into a proper aero position. The # of watts you’re saving is going to be greater if your current position leaves a lot of room for improvement. But you have it right OP. If something saves you 10 watts, make the change & push the same power. You’re going to go faster.
It’s all a bit fuzzy even at the best of times. “10 watts faster” or “10 watts saved” or “10 watts improved over last years model”. Sure, they all may be correct under wind tunnel conditions with an isolated element, but that’s not the way things work.
A disc wheel, for example, is going to test unbelievably amazing in isolation, but when put on the rear of a bicycle the numbers come back to earth. Ditto for aero socks on an isolated leg, shoe covers, handlebars, bottles.
The way I usually think about it is speed gained over a certain setup/position at a given speed.
If I need to push 250w with my setup to go 40km/h. If I introduce this piece of equipment for this power output… do I go faster? How much faster? 0,5kmh? 1kmh?
Obviously, there will be a moment when introducing a new piece of equipment don’t give you anymore “free speedâ€. I may go 40kmh with my position/setup and it is already optimised so if I introduce leg covers they won’t make any difference. What matters here is speed, not watts. You want to be gaining speed for a given power output. That’s the way I see it at least.
Aero is individual and unique. Aero road testing like I did with Desert Dude is very tangible. It is tedious and time consuming, but the output is real. Aero socks may or may not save watts - you won’t know until YOU test. During my testing in addition to fit/position, we tested change of clothes, helmet, hand position, etc. For example, aero helmets are almost universally faster with the vents closed/taped. I was 5w faster with the vent cover off. Very unique to me, but we tested it following specific protocol and there is no question about it.
Also interesting, most folks want to make watt/aero testing linear and cumulative. It is a bit more complicated than that.
Big lesson - you need to test it on YOU to know the benefit (or lack thereof).
Aero is individual and unique. Aero road testing like I did with Desert Dude is very tangible. It is tedious and time consuming, but the output is real. Aero socks may or may not save watts - you won’t know until YOU test. During my testing in addition to fit/position, we tested change of clothes, helmet, hand position, etc. For example, aero helmets are almost universally faster with the vents closed/taped. I was 5w faster with the vent cover off. Very unique to me, but we tested it following specific protocol and there is no question about it.
Also interesting, most folks want to make watt/aero testing linear and cumulative. It is a bit more complicated than that.
Big lesson - you need to test it on YOU to know the benefit (or lack thereof).
EXACTLY!!! I love what you just wrote.
My beef isn’t that aero gains are fake. Quite the contrary. I’m a medium level marginal gainer myself.
My issue is that brands and their marketing departments don’t say what you just said. They quote a savings number and throw it in our faces with no context, making all people believe that’s what they’ll save when the truth is far more complicated.
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
How fast will the OP be at 210 watts in his new aero gear???
This is an example of what some riders like to use to quantify aero gains. Scroll down to the bottom. It converts CDA gains to an actual time and watt saving at a given race speed. In this case rider does HIM at 280w. I calculates a time for a flat course (no wind), and the a a new time for every test we did. So this guy found 23watt, almost 4min. It can be applied to a specific course and wind condition (Kona for example)
Did you forget to include a link???
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
How fast will the OP be at 210 watts in his new aero gear???
This is an example of what some riders like to use to quantify aero gains. Scroll down to the bottom. It converts CDA gains to an actual time and watt saving at a given race speed. In this case rider does HIM at 280w. I calculates a time for a flat course (no wind), and the a a new time for every test we did. So this guy found 23watt, almost 4min. It can be applied to a specific course and wind condition (Kona for example)
Did you forget to include a link???
Click on the highlighted “This”
or
There is always so much focus and talk about saving watts, but I wonder how many people actually understand what it means, I’m not sure I do?
For example, if riding at 210 watts gives me 35 kph and I then put on a disc wheel, aero helmet, calf sleeves etc and save 20 watts does this mean I now only need to put out 190 watts to ride at 35kph?
yes. Exactly
However, when someone claims 10w you have to ask at what speed.
In fact they probably had a CDA decrease of .010. At 45km/h that is about 11.5watts. At 36km/h it is only 6w.
You can make big watt claims if you calculate them at 60km/h (27watts)
How fast will the OP be at 210 watts in his new aero gear???
This is an example of what some riders like to use to quantify aero gains. Scroll down to the bottom. It converts CDA gains to an actual time and watt saving at a given race speed. In this case rider does HIM at 280w. I calculates a time for a flat course (no wind), and the a a new time for every test we did. So this guy found 23watt, almost 4min. It can be applied to a specific course and wind condition (Kona for example)
Did you forget to include a link???
Click on the highlighted “This”
or
https://docs.google.com/...hqz7djC8tAro/pubhtml
Oh thanks, that blue “this” just does not show up very well unless I have my screen at exactly the right angle. 
When ERO sports did their sock test, they found 0.5-6.5 watts savings for different athletes at speeds between 17 and 23mph… and they tested the short version of the sock.
https://youtu.be/DX6imW8o0eQ?si=Or-wH-YVX4umBM29
From our website, the tall version of the sock says: Saves 4-8W (tested 30-45kph) and from what I see, most companies are at least naming an air speed when making wattage claims, and to be totally straight, that’s about all the info most people are willing to even attempt to process.
I’ve been doing this since before anybody believed aero even mattered, and can say that with the advent of power meters, the Watt became the lingua franca of communicating aero and efficiency gains. While it’s certainly imperfect, it’s far better than CdA or grams of drag or anything else that has even less meaning for the consumer… I’d love to just say, ‘reduced CdA by 0.00Xm^2’ but that realistically isn’t going to land well with anybody outside of the secret squirrel society that does this for a living.
My recommendation to people who are interested is to at the bare minimum use a calculator to convert marketing claims into CdA. I like the one at: https://gribble.org/cycling/power_v_speed.html
Super simple to use and will help you get xW at Y speed into CdA and also show the speed per watt change as CdA changes… playing with a tool like this will help your brain start to think in CdA moreso than just watts. Gribble also allows you to plug in Crr data so you can see how those changes affect the power-speed relationship… it’s powerful to see the non-linear relationship between aero watts relative to the linear relationship to the rolling and drivetrain friction losses.
Lastly, the only real way to know anything about any of this is to do your own testing… as I say on my podcast and channel all the time ‘it depends’ and in some instances you might be the person with the 0.5w savings at 17mph or you could be the person saving 6.5w at 23mph… either way, you now ‘know’ and can make decisions on that.