Carbon aero wheels questions

[Schredder]

Besides looking bada$$.... I have the following questions about 50 mm carbon clincher wheels.

1. Are internal nipples worth it relative aero gains versus the extra effort to true a wheel?

2. Help me quantify speed increase over my Boyd Vitesse wheelset. 28 mm Al clinchers. Typical effort (not all out) sees low 20s mph flattish road little wind.

3. When looking at aero wheel data, its the air speed versus ground speed? IOW, a rider will see more gains riding into head wind. Where I live, it is seldom calm with winds often 10-15-20 mph.

Thanks

Chris

[ergott]

about 1/2mph faster, maybe

[echappist]

Besides looking bada$$.... I have the following questions about 50 mm carbon clincher wheels.

1. Are internal nipples worth it relative aero gains versus the extra effort to true a wheel?

2. Help me quantify speed increase over my Boyd Vitesse wheelset. 28 mm Al clinchers. Typical effort (not all out) sees low 20s mph flattish road little wind.

3. When looking at aero wheel data, its the air speed versus ground speed? IOW, a rider will see more gains riding into head wind. Where I live, it is seldom calm with winds often 10-15-20 mph.

Thanks

Chris

1) not worth it

2) for a single front wheel, about 4W at 25 mph at low yaw. At higher yaw, saving become greater. 2W for the rear; for a total of 6W.

3) yes, higher savings when riding into a headwind (catch here is that you also need to exert a greater effort). Riding 15 mph into a 10 mph headwind is the same as riding 25 mph in still air.

[Schredder]

about 1/2mph faster, maybe

You’re not helping to sell new wheels... lol. The marketing gods will strike you down!

[adrien]

1. nope.

2. IME, about 10%. Some of that may be placebo because they sound cool, like Darth Vader's fighter before the franchise became about whiny child actors and people constantly falling off things.

3. Dunno. Never thought about it.

I have noticed very significant gains in two places: first, in rolling hills. At the bottom of a descent, they hold speed notably longer (for example from coast to when you feel the need to pedal again as you start going up). Over a long ride with lots of rollers, this is a real difference; and second, in a pace line...when you come off the front and tuck into the back, the effort required to stay on the train is notably lower. It feels like you're almost being "sucked" forward.

Finally, you didn't ask, but: they feel very different. The stiffness and the responsiveness are addictive, and they feel far more planted than alloy wheels. I compare it to feeling like there's a heavy lead ball loose in the tire, sucking you down.

Above based on Enve 4.5 on steel and Ti bikes.

[Mark McM]

about 1/2mph faster, maybe

I think that number is a bit generous. That kind of speed increase is reasonable if you are comparing 50-60mm aero-wheels to box-section wheels at about 25 mph. The OP asked about comparing to 28mm (semi-deep) wheels at speeds closer to 20 mph, so the speed difference will probably be closer to 1/4 mph.

Bicycle product selection will always be some combination of fashion and function, but for aero-wheels, the proportion of fashion is likely higher than most riders would care to admit. When it comes to speed improvements, aero-wheels are probably only about 4th on the list of equipment selection - and the top three are usually less expensive.

When it comes to performance, the first thing people should look at are tires. It was mentioned earlier that a pair of aerowheels might save about 6 Watts per pair. But if you look at the road tire data on the BicycleRollingResistance web site (https://www.bicyclerollingresistance.com/road-bike-reviews), you'll see that there may be far bigger savings available by good tire selection. For example, if you switch from 25mm Vittoria Rubino Pro G+ 2.0 (16.4 W/each @80psi) to 25mm Continental GP 5000 (10.7 W/Ea @80 psi), you could save 11.4 Watts per pair, or close to twice the savings from a pair of aerowheels (and for about 1/20 the cost).

[Schredder]

Does Ergott mean 1-2 mph or one half? Lol. To further clarify, at my current fitness and position, 23-24 is not terribly difficult again with little wind and flattish grade.

[MaraudingWalrus]

To add my thoughts here (although I'm generally in agreement with Ergott and Mark here):

The actual benefit of much of this stuff is not meaningful to most of us, in terms of things we'll actually notice day in day out. To a professional rider sure, of course...marginal gains and whatnot. To an otherwise extremely fit rider who has done everything else to optimize their performance elsewhere, sure why not.

To most of us who go out on the weekends to have fun while riding...?

As Mark said, much cheaper to get as much/more benefit from making the switch to really nice tires.

Without data on my side to provide hard numbers, there's very few moments in my life of riding where there was actual utility to me in having "go fast" wheels. I simply do not go fast enough, often enough for it to really, actually matter in a real way. Most of us don't.

That said, I have lots of really nice wheels. I build lots of them for other people, too. Nice things are nice, plain and simple. The vanity factor - arbitrary "coolness," the hella awesome "vwoosh vwoosh vwoosh" noise they can make, or looks - plays a bigger role in the value offered by high end wheels to an enthusiast customer.

[oldpotatoe]

Besides looking bada$$.... I have the following questions about 50 mm carbon clincher wheels.

1. Are internal nipples worth it relative aero gains versus the extra effort to true a wheel?

2. Help me quantify speed increase over my Boyd Vitesse wheelset. 28 mm Al clinchers. Typical effort (not all out) sees low 20s mph flattish road little wind.

3. When looking at aero wheel data, its the air speed versus ground speed? IOW, a rider will see more gains riding into head wind. Where I live, it is seldom calm with winds often 10-15-20 mph.

Thanks

Chris

1. NO, particularly when you have to true the wheel..lost in the 'noise'.

2. Really hard cuz it assumes 'all else is equal', from one ride to another. There are probably websites that will do this tho..28mm vs 50mm

3. More gains in a headwind? Considering 85% of the effort to push a bike is overcoming drag, don't thing you will be faster in a headwind. You'll be faster in calm winds than with a headwind. Faster still with a tailwind as long as that wind is > than your velocity.

[Mark McM]

3. When looking at aero wheel data, its the air speed versus ground speed? IOW, a rider will see more gains riding into head wind. Where I live, it is seldom calm with winds often 10-15-20 mph.

Yes and no. A rider will see a higher percentage gain from aero wheels in a headwind, but because their speed is lower, the actual speed increase will be lower.

I put together the equations in a spread sheet, and I used the values for the sample rider found in the analyticcycling web page. This page contains some aero coefficient values for wheels, so I compared a conventional 36 spoke wheel to a disc wheel (single wheel). Here's what I found:

In still air, it took the sample rider 268 Watts to go 25 mph with the 36 spoke wheel. With the disc wheel, the rider would go 25.206 mph with the same power (an increase of 0.802%).

With a 10 mph headwind, at the same power the sample rider's speed decreases to 19.084 mph with the 36 spoke wheels. With the disc wheel the rider would go 19.289 mph (and increase of 1.07%)

A spoked carbon wheel isn't quite as aerodynamic as a disc wheel, but on the other hand, the speed increases by changing both wheels is likely to be more than just one wheel, so you're probably still looking at speed increases of about 1/4 mph (@25 mph) with the carbon aero wheels.

[carpediemracing]

In a headwind aero wheels tend to have less overall benefit. I find they're fastest in a cross-tailwind.

Data supports the first statement - even manufacturers will show that the aero advantage increases as you increase yaw angle.

I have no proof of the second, but I find that with aero wheels I'm able to save quite a bit of energy in a cross tailwind, the difference between hanging on for dear life (or getting shelled) and being comfortable enough think about how to do the final sprint. I had a few situations where I had a flat and a free lap so the conditions were basically identical - same race, same competitors, same wind, just different wheels. It helped that I try to be consistent across my wheels with tires and cassettes.

At lower speeds aero wheels not very helpful also - the % increase isn't as noticeable. You don't have as much aero drag at low speeds.

At higher speeds, so sprints or descents, you'll notice the aero advantage.

I have two sets of clinchers that I used to ride regularly. Both have same tires, same cassette, but one is "very aero" (60/90 Jets) and one is "not aero" (Bastognes aka Ardennes, 18/24H). Same hubs, same spokes, same spoke count. I have one descent I do all the time - it's the short 10% descent to get back to my house, with a 25 mph speed limit, starting at the top of a hard-for-me-hill. I generally start the descent at very low speeds, maybe 8-10 mph, and I generally coast (or soft-pedal without engaging the cassette) down the hill. I also try not to hit 30 mph because I don't want to be "that idiot on the bike" in our 25 mph, 120 house neighborhood. On the non-aero wheels I pretty much brake only to make the hairpin turn. On the aero wheels I have to put the brakes on about 2/3 of the way down because I'm already at 28 mph and increasing.

Given the choice, I do my slow training rides on the non-aero wheels. 14-16 mph, maybe a jump.

If I'm racing (flat/crit only) then I will pretty much only use my aero race wheels (75/90mm - Stingers so basically the same as the Jets just with lighter, stiffer, and better profile rims). They're worth quite a bit if I make it to the sprint, and on windy days they're great - in headwinds I shelter (aero wheels are worthless in that scenerio) and I can fly along in the cross-tailwind sections, more so than the others. I optimize for the fastest conditions, so sprints and cross-tailwinds. The 75/90 happen to be lighter than the Bastognes so there's that too.

[weiwentg]

...
2) for a single front wheel, about 4W at 25 mph at low yaw. At higher yaw, saving become greater. 2W for the rear; for a total of 6W.
...

I recall Josh Poertner saying that the rear wheel is about 80% of the importance of the front wheel, although that goes up (unspecified amount) if it's an aero frame. Basically, a round tubed frame is passing dirty air to the rear wheel, but an aero frame is sending cleaner air through there. In the context of the podcast, it sounded like you could take, say, a 6W average power (weighted by all the yaw angles) and * 0.80.

[bikinchris]

I agree. Aero wheels give more advantage in a crosswind.

[echappist]

I recall Josh Poertner saying that the rear wheel is about 80% of the importance of the front wheel, although that goes up (unspecified amount) if it's an aero frame. Basically, a round tubed frame is passing dirty air to the rear wheel, but an aero frame is sending cleaner air through there. In the context of the podcast, it sounded like you could take, say, a 6W average power (weighted by all the yaw angles) and * 0.80.

Generally, the savings from rear is at 50-60% that of the front. I’m surprised to hear that 80% is given as the low bound

[benb]

You can get them whether they make you faster or not if you want them.

Maybe think about instead what is the opportunity cost of buying the Carbon wheels vs not buying them?

Also all this talk of instantaneous watt savings is marketing driven.

We don't live in a world where time is frozen, and conditions don't stay static.

How long do you actually put out your efforts?

About the longest real world efforts I manage to put in without interruptions due to traffic controls, cars, etc.. is about 10 minutes in day to day riding.

Analytic cycling puts my efforts in the 26-27mph range given a really good day for power output for 10 minutes.

Trust me I never actually average that for 10 minutes. Not on your life. Try more like 23mph. Cause it's never flat. It's never devoid of wind. It's never devoid of a corner I have to go around or a stop sign I have to look very carefully at deciding whether to "roll" through a right turn. Even a car in front of me that slows down to take a left turn is enough to lower my speed a lot and always seems to happen. And the faster you go and the stronger you get the more these things slow you down.

For those kinds of efforts I only see about a 2mph real world difference between my 26lb steel bike that has 32 spoke normal wheels and my 16lb carbon bike that has "aero" alloy wheels.

How may bikes do you have? If you were looking at buying something like ENVEs or high end Zipps the opportunity cost could be that you could buy a set of alloy wheels with an entire extra bike attached to it. Carbon wheels vs a new gravel bike or MTB or a rainy day training/commuting bike... Lots of other things you can do with the money outside of cycling too. Or use it for a vacation where you get do some amazing riding. A Carbon wheelset would make a nice start on a savings account for a trip to ride in the Alps in a year or two when "You know What" is gone.

Only you can decide. If the fancy wheels are worth 1/4-1/2mph at 25mph in fantasy land and I average 4mph less in the real world than my power output in fantasy land says I can go the Carbon wheels are not worth it for me. The physics of the wheels can be real but you end up not being able to take advantage of them anyway even if you're strong enough.

If you're racing and you get out in a break where there are no cars or traffic controls maybe they come into play as being something you can actually take advantage of.

For me an Aero Helmet has mostly been worth it. Not a TT helmet just a helmet with some "aero" influence. The cost difference is minimal compared to stuff like Carbon wheels.

[Mark McM]

I agree. Aero wheels give more advantage in a crosswind.

Yes, that's true, well designed aero wheels have greater drag reductions in cross-winds. In fact, if the cross-wind conditions are just right, some aero wheels can even exhibit a sail effect, in which the wheels actually add some propulsion - although these conditions are quite rare, and the extra propulsion is very small.

Just for giggles and yucks, I went back to my spreadsheet equations to see what would happen if the aero-wheel drag as zero. At a power of 268 Watts and no wind, the sample rider increased their speed from 25 mph (with 36 spoke standard wheels) to 25.77 mph (with wheels that had zero drag).

Even in a perfect world the speed increase with aero wheels will be well under 1 mph, and in the real world the speed increases a rider is likely to see is just a small fraction of 1 mph. Quite often in advertising for aero wheels you'll see no quantitative claims at all, and even when there are, the numbers given will be things like CdA, grams of drag, or Watts saved, which the average cyclist will have trouble correlating to real speed increases. If instead they advertised speed increases smaller than the speed display resolution of most cycling computers, they probably wouldn't sell as many wheels.

[cgates66]

Yes, that's true, well designed aero wheels have greater drag reductions in cross-winds. In fact, if the cross-wind conditions are just right, some aero wheels can even exhibit a sail effect, in which the wheels actually add some propulsion - although these conditions are quite rare, and the extra propulsion is very small.

Just for giggles and yucks, I went back to my spreadsheet equations to see what would happen if the aero-wheel drag as zero. At a power of 268 Watts and no wind, the sample rider increased their speed from 25 mph (with 36 spoke standard wheels) to 25.77 mph (with wheels that had zero drag).

Even in a perfect world the speed increase with aero wheels will be well under 1 mph, and in the real world the speed increases a rider is likely to see is just a small fraction of 1 mph. Quite often in advertising for aero wheels you'll see no quantitative claims at all, and even when there are, the numbers given will be things like CdA, grams of drag, or Watts saved, which the average cyclist will have trouble correlating to real speed increases. If instead they advertised speed increases smaller than the speed display resolution of most cycling computers, they probably wouldn't sell as many wheels.

Spot-on. Aero wheel advertising is massively optimistic. Their data is right, but it's not often relevant.

For me, deep-section wheels have the advantage of great stiffness via a better bracing angle and a stiffer / stronger (although more brittle) rim. If I get a little benefit in an ideal, non-turbulent crosswind - great. The marginal gains are probably valuable to racers who are more or less evenly matched otherwise, of course. And they look the business, on the right frames (for some reason, I like the look of shallow wheels on old-school, steel frames with steel forks - on modern frames, carbon it is).

[uber]

Maybe it is the aerodynamics, or the weights of wheels or all in my head, but I feel like a set of 50-60mm depth wheels has me going the same speed with a bit less effort than 35mm rim depth. I question if I would be going faster on a conventional round tube bike with deeper rim depth or an aero frame bike with mid depth wheels? Probably the same marginal physical differences with the rest being in my head? Hah.

[fogrider]

Aero wheels are faster. where it matters most is on flat to rolling terrain. They're stiff and responsive. You'll be able to hold speed longer, and if you need some speed to jump on someone's wheel...

[joshatsilca]

The real problem with this type of aerodynamic problem is that if you are holding constant power, your aero gains are directly translating to more speed, and the power required to go at that faster speed is increasing at the cube of the velocity.. so each aero gain makes the next one that much harder as the velocity keeps increasing and the power requirement geometrically.. which is why the hour record is such a fun puzzle to try and solve.

We have beta version power calculator on our site https://silca.cc/pages/power-calc which allows you to see the power required to go a certain velocity (working on the one that will go both directions currently..)

The calculator works in CdA and decent CdA approximation for a good road position with semi-aero 28mm wheels might be 0.3m^2 and moving to Zipp 404 or ENVE 5.6 might get you to 0.28m^2

At 24mph, this CdA change is worth about 13 watts and at 30mph it's worth about 30 watts.

The other way to think about this is that for most racing (non TT) you are going at the speed of the race.. so the advantages of aero come as power and energy savings most of the time, and then really show up when all hell breaks loose and somebody attacks or you are trying to close a gap, sprinting, etc.. If you think of racing as a series of bifurcation points, where the field separates at numerous points or very high intensity, gains like these can allow you to hang on that little bit longer, better hold the wheel in front of you, etc.. or if you are driving/attacking/sprinting they can allow you to push the other riders too deep into the red, snap the elastic to get them out of your draft or pick up extra inches in the sprint.

[nooneline]

The real problem with this type of aerodynamic problem is that if you are holding constant power, your aero gains are directly translating to more speed, and the power required to go at that faster speed is increasing at the cube of the velocity.. so each aero gain makes the next one that much harder as the velocity keeps increasing and the power requirement geometrically.. which is why the hour record is such a fun puzzle to try and solve.

We have beta version power calculator on our site https://silca.cc/pages/power-calc which allows you to see the power required to go a certain velocity (working on the one that will go both directions currently..)

The calculator works in CdA and decent CdA approximation for a good road position with semi-aero 28mm wheels might be 0.3m^2 and moving to Zipp 404 or ENVE 5.6 might get you to 0.28m^2

At 24mph, this CdA change is worth about 13 watts and at 30mph it's worth about 30 watts.

The other way to think about this is that for most racing (non TT) you are going at the speed of the race.. so the advantages of aero come as power and energy savings most of the time, and then really show up when all hell breaks loose and somebody attacks or you are trying to close a gap, sprinting, etc.. If you think of racing as a series of bifurcation points, where the field separates at numerous points or very high intensity, gains like these can allow you to hang on that little bit longer, better hold the wheel in front of you, etc.. or if you are driving/attacking/sprinting they can allow you to push the other riders too deep into the red, snap the elastic to get them out of your draft or pick up extra inches in the sprint.

This is a great post that goes to show that while aero wheels might feel a little bit nice for general riding, they can be vital for racing - even in amateur racing there are extended shakeouts well above 30mph that, with environmental features (like crosswinds or certain corners) guarantee that it's better to be at the front and it's hard to hold on. 30w at 30mph makes the difference between making the break and not - or holding on in an echelon vs getting dropped. At higher speeds? More watts. Even an extra 1 mph makes the difference between completing the bridge and not, or being able to roll into top tier launch position for the sprint or just tucking tail outside the top ten.

[benb]

This is a great post that goes to show that while aero wheels might feel a little bit nice for general riding, they can be vital for racing - even in amateur racing there are extended shakeouts well above 30mph that, with environmental features (like crosswinds or certain corners) guarantee that it's better to be at the front and it's hard to hold on. 30w at 30mph makes the difference between making the break and not - or holding on in an echelon vs getting dropped. At higher speeds? More watts. Even an extra 1 mph makes the difference between completing the bridge and not, or being able to roll into top tier launch position for the sprint or just tucking tail outside the top ten.

This is the typical equipment stuff though.

He compared the CdA of the two wheels.

The Wheels don't go down the road by themselves.

0.02m^2 difference in the wheels is what he quoted.

There are 10x or more that in gains/losses in just your posture on the bike. Totally free to work on.

[echappist]

The calculator works in CdA and decent CdA approximation for a good road position with semi-aero 28mm wheels might be 0.3m^2 and moving to Zipp 404 or ENVE 5.6 might get you to 0.28m^2

At 24mph, this CdA change is worth about 13 watts and at 30mph it's worth about 30 watts.



Could you clarify if that is averaged over typical yaw angles, or is that for specific yaw angle? Also, is the assumption that the 28-mm rim is traditional deep-V or is it assuming its performance would be on par with the Zipp 101 rim/ Flo 30/ etc? Lastly, is that for both wheels or just for the front?

[ergott]

There are 10x or more that in gains/losses in just your posture on the bike. Totally free to work on.

Or you can do both. Personal improvements and equipment improvements are not mutually exclusive.

[joshatsilca]

This is the typical equipment stuff though.

He compared the CdA of the two wheels.

The Wheels don't go down the road by themselves.

0.02m^2 difference in the wheels is what he quoted.

There are 10x or more that in gains/losses in just your posture on the bike. Totally free to work on.

Absolutely, but remember that things like posture and equipment upgrades are not mutually exclusive. So my example of a 0.3 CdA would mean that you had your position pretty darn dialed.. the beauty of talking in CdA here is that it's relatively additive (some things can have interactive effects when you get really granular.), so if your position isn't dialed and you start at 0.5 m^2, you can dial your position to 0.3 m^2 on your current bike.. take it to 0.28 with aero wheels.. 0.27 with a better frame, 0.25 with integrated aero bar/stem.. 0.24 with more aero helmet.. aero clothing, etc.. somebody skilled in the art can probably get a road position to in the low 0.21-23 range for a <6ft very fit athlete on great equipment, probably get into the 0.18x range on a TT bike

Bradley Wiggins is 6'3" and had a CdA of 0.198 m^2 (edit, sorry, 0.172 was Obree!) for his hour record which was the result of dozens of hours of tunnel and track testing for his position combined with hundreds of hours of equipment modification and testing. And probably most importantly, hundreds of hours of training in that ultimate position to ensure he could maintain it AND maintain power for the 1 hour.

[benb]

Yah but are you talking about the wheels reducing the CdA of the entire ride/bike system by 0.02 or are you talking about a difference in just the wheels?

This stuff is impossible for me to put any faith in anyway without a published peer reviewed paper (which do exist).

Everything coming out of the bike companies always, always looks suspect, it never looks like it was done at a high enough level in terms of professionalism/documentation/science to pass muster.

You can't even tell if someone is even calculating the figures correctly.

Wiggins got his 0.172 on a TT bike with aero bars + aero helmet right + skin suit and aero shoe covers and the whole 9 yards right? That's my point, if he gets on the hoods all of a sudden he's at 0.300+. For most of us a 0.02 difference (if it's real) just doesn't matter.

Get em cause they're bling or you like the placebo effect but if you're not TTing at a super high level it's not going to get you results.

0.02 off a 0.174 when you are TTing for an hour at 30mph+ is not the same thing as 0.02 off a 0.45 when you're out riding 17mph average speed in traffic or when you're in an amateur race mostly in a pack.

The guy whose riding at 0.3-0.4 out in the real world should be more concerned about not sitting up than spending thousands on these wheels. Or at least just get the wheels as bling and don't expect much.

[flying]

they feel far more planted than alloy wheels. I compare it to feeling like there's a heavy lead ball loose in the tire, sucking you down.



Heheh somehow a heavy lead ball sucking me down does not sound like a good thing for wheels ;):)

Joking: ;)

[joshatsilca]

Yah but are you talking about the wheels reducing the CdA of the entire ride/bike system by 0.02 or are you talking about a difference in just the wheels?

This stuff is impossible for me to put any faith in anyway without a published peer reviewed paper (which do exist).

Everything coming out of the bike companies always, always looks suspect, it never looks like it was done at a high enough level in terms of professionalism/documentation/science to pass muster.

You can't even tell if someone is even calculating the figures correctly.

Wiggins got his 0.172 on a TT bike with aero bars + aero helmet right + skin suit and aero shoe covers and the whole 9 yards right? That's my point, if he gets on the hoods all of a sudden he's at 0.300+. For most of us a 0.02 difference (if it's real) just doesn't matter.

Get em cause they're bling or you like the placebo effect but if you're not TTing at a super high level it's not going to get you results.

0.02 off a 0.174 when you are TTing for an hour at 30mph+ is not the same thing as 0.02 off a 0.45 when you're out riding 17mph average speed in traffic or when you're in an amateur race mostly in a pack.

The guy whose riding at 0.3-0.4 out in the real world should be more concerned about not sitting up than spending thousands on these wheels. Or at least just get the wheels as bling and don't expect much.

Yes, 0.02 is what you'd expect to see in overall CdA change when swapping wheels.. from there, it's really what you are after and what's important to you. If you're at 0.5 and riding by yourself for fitness and fun, I'd go with what's comfortable and what you like the looks of, etc.. and if you are racing, the question becomes how/when are you getting dropped or failing to drop others.. personally, we have a 22mile loop here in Indy that sees a very fast 1/2 field every Tuesday/Thursday and experiences 5 separate and very predictable attacking points where things go nuts for 4-5 minutes and then settling out, but don't regroup. For me, a set of aero wheels is the difference in making it to the end of the ride with the field vs getting shelled in one of the first 2 efforts.. I can do 350w for 4-5 minutes, but can't do 375 for that long, so for my enjoyment of that particular ride, it matters. However, when I go out by myself on a saturday morning for an hour or when I commute to work, it really doesn't matter and other than placebo effect I can't say I can ever tell what wheels I'm on.

Also, I brain farted and dropped Obree's 0.172 into my original post and not Wiggins 0.198, but that also highlights the importance of CdA that Obree essentially matched the Dowsett record that Wiggins had to beat, but Obree achieved that record on some 45 fewer watts than Dowsett (CdA 0.189) and some 80+ watts less than Wiggins at 0.198

[hobbanero]

I think it is basically an engineering fact that deep aero wheels are faster at the coffee shop.

While they are a ways down the aero upgrade hierarchy (body position, supertight clothing, aero helmet, frame), 50mm carbon wheels look correct on a modern carbon bike. And style watts are real.....just like propulsion watts, they add to cycling enjoyment.

[Mark McM]

Yes, 0.02 is what you'd expect to see in overall CdA change when swapping wheels.. from there, it's really what you are after and what's important to you. If you're at 0.5 and riding by yourself for fitness and fun, I'd go with what's comfortable and what you like the looks of, etc.. and if you are racing, the question becomes how/when are you getting dropped or failing to drop others.. personally, we have a 22mile loop here in Indy that sees a very fast 1/2 field every Tuesday/Thursday and experiences 5 separate and very predictable attacking points where things go nuts for 4-5 minutes and then settling out, but don't regroup. For me, a set of aero wheels is the difference in making it to the end of the ride with the field vs getting shelled in one of the first 2 efforts.. I can do 350w for 4-5 minutes, but can't do 375 for that long, so for my enjoyment of that particular ride, it matters. However, when I go out by myself on a saturday morning for an hour or when I commute to work, it really doesn't matter and other than placebo effect I can't say I can ever tell what wheels I'm on.

When you ask, "do aero wheels make a difference", you first have to define what "make a difference" means. In racing, the difference between 1st and 2nd are often separated by fractions of a percent, so any improvement, even small ones, "make a difference". Even the difference between barely-hanging-on and just-losing-contact can be quite small. But in other cases, such as when you're just out riding for fun, in differences in many percentage points hardly matters.

The original poster asked if his speed difference between two different pairs of wheels could be quantified (riding solo at speeds in the low 20s mph). While we can only make loose estimations, It's a good bet that it would be just a fraction of 1 mph. Does that "make a difference"? That's up to him to decide.

[mtechnica]

Aero wheels are faster by all accounts so there’s that.

[Schredder]

When you ask, "do aero wheels make a difference", you first have to define what "make a difference" means. In racing, the difference between 1st and 2nd are often separated by fractions of a percent, so any improvement, even small ones, "make a difference". Even the difference between barely-hanging-on and just-losing-contact can be quite small. But in other cases, such as when you're just out riding for fun, in differences in many percentage points hardly matters.

The original poster asked if his speed difference between two different pairs of wheels could be quantified (riding solo at speeds in the low 20s mph). While we can only make loose estimations, It's a good bet that it would be just a fraction of 1 mph. Does that "make a difference"? That's up to him to decide.

OP here
First, thanks everyone for sharing their knowledge and experience!

Lots of information to digest and think about.

Another quantitative aero question. Probably harder to answer, but what average speed improvement might I realize over a ride that I currently average 20 mph for 26 miles 1100 feet of climbing. The ride is a loop with wind often 10 to 20 mph?

Chris

[FriarQuade]

Wheels in this era don't go out of true all that often so I see the internal nipples as a pretty small concession to speed. Is it harder to true internal nipple wheels, absolutely. But if you only have to do it once a year does it really matter? If you're running discs then it's non issue.

[Mark McM]

OP here
First, thanks everyone for sharing their knowledge and experience!

Lots of information to digest and think about.

Another quantitative aero question. Probably harder to answer, but what average speed improvement might I realize over a ride that I currently average 20 mph for 26 miles 1100 feet of climbing. The ride is a loop with wind often 10 to 20 mph?

There's a whole lot of variables here, involving the rider, the bike, and the course, so it's hard to give even a rough estimate based on the information known. However, others have attempted to model specific courses under specific conditions, which might be interesting to look at. For example, the folks over at FLO Cycling, a maker of aero wheels, have modeled time savings over specfic Ironman triathlon cycling courses:

https://flocycling.com/blogs/blog/flo-cycling-aero-vs-weight-follow-up

The most interesting one here is the Ironman Coeur d'Alene course, which has 4612 feet of elevation gain over 112 miles (close to the same elevation gain per mile as your course). They modeled it with their sample cyclist using a pair of FLO 30 wheels (30mm deep aluminum rim) vs. using a FLO 90 (90mm deep carbon rim) front wheel and FLO DISC disc rear wheel. At an average 250 Watts power, their example cyclist completed the course in 6 hr, 1 min, 36 sec (18.58 mph Avg) with the FLO 30s, and 5 hr, 55 min, 46 sec (18.88 mph Avg) with the FLO 90/Disc wheels. You asked about 50mm deep carbon rims, which are apt to be less aerodynamic than a 90mm rim plus disc wheel, so I'd expect the time savings/speed increase to be less as well.

[benb]

The Ironman test data is no drafting on a closed course though right?

6 minutes over 6 hours would completely be in the noise if you were riding with other riders or in real world events. Unless you're P/1/2 you're probably not even going to be in a 6 hour race and it seems like a closed course race is the only case where real world variances don't dwarf the savings. Even a Gran Fondo type ride you can get caught up at stop lights or a train crossing and all this stuff instantly vanishes into the noise.

To me it's all about whether the real world makes these gains imperceptible.

6 minutes over 6 hours is lost if you have to take an extra bathroom break. It's lower than the variance over a real world course if you rode the same course 2x and one of the times you got lucky and got more green lights.

If you take it down to 1 hour in a naive way they're saying 1 minute saved over an hour.. think how easy it is to lose or gain 1 minute due to external things.

You'll never be able to tell.. either just buy them and be fine with that or decide they're not worth it.

This is just me.. I'm practical enough I kind of regret having a bike with internal cable routing for supposed aero benefits just cause of the extra maintenance inconvenience.

About the only aero things I don't think are a big inconvenience are an aero helmet and a better fitting jersey.

[Mark McM]

The Ironman test data is no drafting on a closed course though right?.

Yes, but that helps in limiting variables. If you try to add in drafting and group dynamics, you've got too many factors to consider. I've been racing on some of the same courses here in New England for years, and the racing speeds can vary widely, depending on who's in the field and how they want to race. If there are a few teams that want to work to keep the group together until the final sprint, then riding in the pack can be relatively easy even though the average speeds are high. Or, if there are several teams that are relying on getting one or more of their riders away in a small break, there could be many attacks & chases, and the race could be very hard even if the average speed is lower.

[benb]

Having been to Kona several times and watching the way people ride there and talking to them it could not be a further planet from roadies in New England or Europe. It's a completely different sport. :eek: This stuff makes sense to them.

Everybody riding by themself even "training" in full aero kit + TT helmet + aero/TT/Tri bike riding down the side of the highway 25-50 miles in one direction and then taking a U-turn and going back along the side of the same highway.

One rider I talked to there had been doing that on the same stretch of the highway (part of the course) for decades 2-3 times a week.

Just totally different kind of riding.

There's just no way I'll ever ride in a way that limits the variables that much where I'd ever be able to quantify my equipment.

We have these debates about whether or not these parts help X amount and we're mostly talking about performance in a wind tunnel.

All I'm getting at here is unless you ride on a trainer in a wind tunnel you might never even know if it's doing anything for you.

The best way to use these wheels is to borrow them from your friend who buys everything in sight the week before a big race.

[robertbb]

About the only aero things I don't think are a big inconvenience are an aero helmet and a better fitting jersey.

And they also happen to be the cheapest AND with the biggest impact.

[martl]

Yes, but that helps in limiting variables. If you try to add in drafting and group dynamics, you've got too many factors to consider. I've been racing on some of the same courses here in New England for years, and the racing speeds can vary widely, depending on who's in the field and how they want to race. If there are a few teams that want to work to keep the group together until the final sprint, then riding in the pack can be relatively easy even though the average speeds are high. Or, if there are several teams that are relying on getting one or more of their riders away in a small break, there could be many attacks & chases, and the race could be very hard even if the average speed is lower.
Flo Cycling is trying to sell aero wheels. They also have in the past not exactly excelled with their understanding of technology. I would take their calculations with several grains of salt.

[mcteague]

Flo Cycling is trying to sell aero wheels. They also have in the past not exactly excelled with their understanding of technology. I would take their calculations with several grains of salt.

Yeah, I take ANY claims that result from wind tunnel tests with large grains of salt. The real world does not come close to behaving like a wind tunnel at bike speeds as they all seem to test at steady state.

Transient vs Steady State drag

The concept of transient drag effects have been well noted in low speed Aerospace applications such as military reconnaissance drones. This transient concept has not been applied to bicycle related products despite the overwhelming sensitivity of the velocity vectors involved. As an example the crosswind velocity on a bike often exceeds the forward velocity (Ratio > 1). A comparison for a car would yield a forward to crosswind ratio of 0.25 at 100km/h typical cruising speed.

https://www.hambini.com/testing-to-find-the-fastest-bicycle-wheels/

Tim