Aero Wheels - What they are NOT telling you!

welcome to sunny Brittany it's fantastic weather forecast we've got for the next few days so making the most of that and this video is about the arrow testing that the major wheel companies do and what they're not doing and what they're not telling you because as we all know one of the big selling factors of we all see stage is their arrow performance and every single company will tell you that theirs is the best they got they got the best shape they got the best for four months that's this your angle and they beat all the others and everyone's trying to outdo each other basically on arrow when if you look at the actual rim shape of all these wheels they're all pretty much the same I mean they all produce a 3050 an 80 mil rim and if you look at them all I mean you're splitting hairs between between Enya's and little pretty much the same shape so it's very hard for them to kind of differentiate theirs from someone else's because the arrow performance of all these rims is going to be extremely similar but the thing that they're not doing and they're not testing for is rotational drag now this is something that I've always considered to be important and in an earlier video in fact one of the very first videos I did I tried to do the kind of basic experiment to demonstrate a little bit the effects of rotational drag now I'll be the first on hands up and say that video was was fraud it was pretty basic he didn't have enough I didn't have a speed sensor on the wheel I could have done it a lot better but all I was trying to do was just try and show that rotational drag is important and that you can even show the difference in two wheels just when I stand like this just purely how well they perform in a stationary situation which obviously is not ideal because there's no wearing and moving across them but it's still going to give you an idea of how they're going to perform in in real life I mean if a wheel performs extremely well in a safety situation you can suppose that it's going to do fairly well in a in a translation situation so what are we actually looking at here I mean when we talk about translational drag it's the the drag where the air is moving across the wheel like this and rotational drag obviously is the power to spin it's how much power do you have to put in to actually make that wheel spin and DT twist has just come out with quite a detailed study on rotational fragile in wheels and you can see it here and they're talking about as much as 25% of the overall drag being down to rotational rotational drag so it's an extremely important aspect of the Aero performance of your wheel and yet no one's really been talking about it if you go and look at the jig and Reynolds websites they hardly even mention it and yet you have a company like DT Swiss a respective company telling you that ya up to 25% of everything that's going on here it's the answer location of drag and we know full well that bladed spokes are where it's at for Aero efficiency you have companies hiding do the nipples whether they're not they're not in the air flow so it's out there people know about it but when you have a narrow aero data from companies like zip and and NV and they're talking about yeah it's great additional angle and that's important sure but you are not getting the full picture if they're not telling you the power required to spin the wheel and albeit you have a guy on a bike and on rollers in the wind tunnel and the wheel is spinning so it's creating a sort of kind of real-world condition where the wheel is is spinning if you don't measure the power it takes to spin that wheel then you are neglecting an important component of what's going on and you know it's no point saying yeah I will is the best by 0.5 of a watt when potentially it could be worse by 3 or 4 watts and when it comes to actually spinning that wheel so I think the reason why they haven't you we focus so much on that is because it's quite difficult to do this expensive you have to you have to have a kind of special rig with a motor that that's spinning the wheel so you can measure the exact power it is taking to spin that wheel and I'm just in the basic experiment I did you can see how the light weight was spilling down from 42 kilometers an hour to 20 kilometers an hour much slower than the Karima was and that has been borne out also in the real-world test room that I've done where the creamer is also showing that it's slightly worse error performance and I mean I'm convinced that's down to error rotational rotational drag basically the kareem has big fat spokes which are not arrow at all this circular are not bladed and that has to has a penalizing error effect and although yeah when you do a basic spin up test like this you have bearing drag also of course but the the main the main thing going on at high speeds ie above sort of 35 40 kilometers an hour the main factor is arrow drag because as we all know arrow drag increases with the square of your speed so the faster you go the more and more arrow becomes becomes a factor bearing drag is just linear bearing drag just goes along like this and so will increase slightly as it gets faster faster but arrow drag is is exponential so it will go up like this and become more more the factor and you could hear in that video just the noise of the spinning of the spinning wheel was down to the spokes the spokes are moving a lot of their you know when when they're moving around there's there's 16 20 of them 20 24 of them and they're all crashing away at the air and the tips especially have a very high velocity because they have to go around further so this is partly why a deeper in is more errors not just because of its translational properties through the air but also because the spoke is shorter and you have less attacking and less spoke at a key in the air so you know basically I would say that a lot of the advertising's you see for these wheels it doesn't mean really if you're not if you're not looking at the rotational drag as well they're leaving out a quarter of the picture and their comparisons are pretty much worthless so ham beanie is a fellow's truth gorilla who has looked a lot this arrow stuff in detail and although we're both engineers he's the arrow engineer I'm a mechanical engineer so I'm not I don't claim any great credentials as far as it comes to high-end aerodynamics but you know so have a look at some of his videos he's he's kind of concluding the same the same kind of things and yeah I mean just just be aware that if you're buying wheel like as if we're three has there been any testing done and any optimizations done for its rotational rotational drag I would think so but is there any data on it I haven't seen any so I don't know and I and I think DT Swiss is definitely going the right way in publicizing it and optimizing their rotational drag and I think it's I think it's really important

Channel: Cyclespeed Tours

Views: 156,031

Rating: 4.1170568 out of 5

Keywords: Zipp, Enve, Reynolds, Lightweight, Corima, aero wheels, aero drag, spokes, rotational drag, wind tunnel

Id: YfPRu6APOhg

Length: 7min 44sec (464 seconds)

Published: Fri Jun 16 2017