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#1
07-28-2020, 07:10 PM
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Carbon aero wheels questions
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 
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#2
07-28-2020, 07:27 PM
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about 1/2mph faster, maybe
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#3
07-28-2020, 07:37 PM
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Quote:
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.
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#5
07-28-2020, 08:49 PM
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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.
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#6
07-28-2020, 09:23 PM
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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, 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). Last edited by Mark McM; 07-28-2020 at 09:25 PM.
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#8
07-28-2020, 09:44 PM
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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.
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#9
07-29-2020, 08:07 AM
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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.
__________________
Chisholm's Custom Wheels Qui Si Parla Campagnolo
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#10
07-29-2020, 10:39 AM
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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.
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#11
07-29-2020, 11:13 AM
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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.
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#12
07-29-2020, 12:03 PM
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#13
07-29-2020, 12:34 PM
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I agree. Aero wheels give more advantage in a crosswind.
__________________
Forgive me for posting dumb stuff. Chris Little Rock, AR
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#14
07-29-2020, 12:52 PM
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#15
07-29-2020, 01:38 PM
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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. Last edited by benb; 07-29-2020 at 01:43 PM.
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