#46
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#47
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#48
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Using the Swiss Side data as an example, if the yaw angle was the very unusual 15 degrees, their 62mm wheel would save about 5 watts over the 50mm wheel for the few seconds that the rider was going down the road at the perfect angle and with a consistent wind to generate that yaw number. Again, the Swiss Side data was determined with wheels that are not in a frame, and not riding with other riders, so the real world would reveal less of a difference. If the yaw angle was the freakish 20 degrees the difference becomes significant with these wheels (but perhaps not others like the Boras). However, who even rides when it's that windy? When I raced I took whatever nature threw as us. Now that I don't race, that kind of wind keeps me and everyone I know on the couch. That definitely would not be fun with 62mm wheels. The wheel companies don't mention that the wind speed is not what the weather report says, or up in the waving trees. The wind has to be fast enough at axle height to generate 20 degrees of yaw, and if it's that windy at 14 inches it is a helluva day. . Last edited by 9tubes; 05-17-2022 at 05:07 PM. |
#49
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There have been a number of yaw angle studies but here is one that is pretty typical that I clipped from November Wheels. It shows the time at 15° or above of yaw is tiny. The Hambini article shows a bit more amount of time at higher yaw angles but that is in windy England.
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#50
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Last edited by Likes2ridefar; 05-17-2022 at 05:35 PM. |
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#52
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It looks the the chart reads 2.5% for 15 degrees, 2% for 17.5 degrees, and <2% for 20 degrees. That totals to about 6%.
Yep, for 6% of the time the a rider can save 5 watts, which translates to an extra 0.14 mph at the test speed they used (28mph). Then decrease that number because the both wheels are in a frame and not standing alone in a wind tunnel, and decrease again because we can expect a wheel seller to make all assumptions and setup choices to maximize the difference. So less than a tenth of one mph? A rider can weigh that (pun intended) against the additional weight of taller rims and the crosswind negatives. Then weigh that with how cool they think tall rims look. And if a rider likes disc brakes, that person might consider that the extra spoke count, extra spoke length, and the disc might make more aero difference than 50mm vs 62mm. Just a thought. . Last edited by 9tubes; 05-18-2022 at 08:26 PM. |
#53
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Well, I'm just a simple nobody who likes to ride bikes. I can't spout no fancy numbers, or interpret charts or otherwise act like I know the "real deal" and what I'm talking about.
All I know is under me on a calm day when I'm riding hard enough to spend significant time above 21 mph (riding solo always) a deeper wheel is easier for me to carry the higher speeds for greater distance before I blow up. They actually do give the sensation of "taking off" and making it feel easier. I can usually even see a higher avg speed for that section while the HR is lower. Case in point the old Fausto Coppi I built up last Friday and rode the first several rides on with shallow open pro rims. On the one good calm ride using these I felt really great and made up significant time on the return leg getting in the drops and working hard. Today I did the same basic route but using a deeper set of Mavic Cosmics. The total bike weight was a full oz lighter with these wheels. Today though I felt like crap, actually took the day off work because my knees were a mess from being abused at the VA hospital yesterday. It took me about the first 5 miles before the knees stopped feeling stiff and I was about to spin freely. I still didn't feel like I had any energy though. But like a couple of days ago I got in the drops and went after it on the return leg. The long sections I cranked at the higher speeds felt easier, HR and respirations were lower, and the avg speed over those segments was higher. Overall avg pace over the 24+ mile route was higher too. Yet I really did feel like crap the whole ride. So..... I can't say with any certainty that the deeper wheels made a difference but it sure felt like it on the ride and seems to be supported by my ride data. So yeah, I'll keep me some bikes around with deeper wheels because I've experienced the same thing many times as I "upgraded" other bikes I had a lot of seat time on. It really is a simple as that for me. It's just a given they are faster when used in the right situations. As much so as the fact we all know red bikes are faster. |
#54
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So maybe for many, deep sections are always faster, but it has nothing to do with drag. Feel fast be fast.
The notion of diminishing returns and less absolute returns than is immediately intuitive is somewhat freeing though. The reason I want deeper sections is like 75% aesthetic though. But at least now I can admit it to myself. Sent from my iPhone using Tapatalk |
#55
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This does not look as good, as this. And this does not look as good, as this. And then this, or this. In each example to me the looks are improved as well as the performance except on maybe the windiest days. And I really want to put something really deep on this bike to see what it gives me. This may be my first BTLOS buy as I'd like to go at least 60mm deep on the rear with something shallower up front. Last edited by jamesdak; 05-20-2022 at 07:05 AM. |
#56
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Those are good looking bikes! Agreed that on the more aero focused ones some deeper sections would look nice. I’m loving that klein though… something about it really resonates.
Sent from my iPhone using Tapatalk |
#57
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#58
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The thing to think about is that even if you spent whatever significant amount of time beyond 10* or 12* of yaw, none of those points are concentrated. So you might spend a few percent between 20* and 30*, another few percent between 30* and 40*, and so on out to a dead tailwind. In speaking to a lot of people from wind tunnel engineers to Ironman Kona runner-up triathlete to random bike aero experts, no one tests outside of 20* and a lot just test within 10*. Easy to see why - you aren't getting any heft at any points outside of that, so what does it even matter if you see a big benefit spike at 43*? The sail effect definitely happens, I've absolutely felt it on 50mm deep wheels and even shallower. But it's unpredictable in extremis and I've ridden I don't know how many thousands of miles on 40+mm deep wheels in a place that I originally chose to live in because it's windy (I race sailboats), and I've felt it a handful of times. After all of that study and feedback from customers and blah blah blah my takeaways are: 1. Ride what you think is going to look good 2. Most people seem to enjoy the feel of lightweight more than the benefit of aero (confirmation bias may dominate this) 3. Matching your tire width to your rim width is the most important element of aero speed and even more so stability As I said in another discussion today, I currently mostly use 38mm deep x 32mm outside/25mm inside wheels for gravel (with 38s) and 50mm deep x 32mm outside/25mm inside for road (with 30s). I have a zillion other wheels hanging from pegs but those are the ones I like best and use most. |
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