Very intresting, ive rode many carbon wheelset and they feel great because of the lightness however there has always been something about them that has always made them feel flexy, as a heavier rider. This may very well explain my preference towards alloy wheels. Thank you bill!
Nice design of experiment and execution. I didn’t know why rear wheel that seldom experiencing a side load is chosen as an example (L/R asymmetrical spoke tension) . Should front wheel be taken in the experiment instead? A wheel that frequently experiencing side load? (Symmetrical tensioning)
Great video. At 6:56, wouldn’t you say it would be more appropriate to have 2 lines originating from the hub and ending at the spoke anchors? The spokes at the top half and bottom half seem to be at different angles. For example, I think the lower half of the spokes are at a 3.1% angle. I also have a hypothesis that deeper rims lead to more deflection at the bottom end between the spoke anchor point and the bead seat. Could you do this experiment with an alloy rim and see how much deflection there is between the spoke anchor “hinge point” and bead seat?
How about quality carbon rims? How do they perform in the same test? Interesting stuff! I just ordered my Yoeleo 50 mm wheels and have very little clearance in my bike frame with the 40 mm tires that I am using, so we'll see how that turns out :) Thanks for the insightful video!
Dave, maybe it is, but then you get more rain and crud being thrown up into the brakes. A better solution is deep section rims that are designed to flex less. My guess is that they will inevitably be heavier, though.
Great video! Not that it matters a lot, but I think you made a small error in calculating the slope for the inner section. That should be (-7.21 - 3.83) / (622 - 2 * 85) = -2.4% instead of -4.2% I guess.
Ben, thanks. Maybe so, but as you said, it really doesn't change the result. I had seen the effects of this kind of rim deflection before, but I really didn't understand it until I did the experiment.
Interesting. This looks to me like another reason disc brakes could be desirable, at least on deep-section aerodynamic wheels: being part of the hub (as opposed to the rim) they would experience no flex whatsoever from the lateral forces described in the video. While the performance of having longer spokes with an aerodynamic fairing seem beneficial, the act of truing wheels with deeply recessed nipples must be a huge pain in the ass, not least of all because doing so would require custom-built tools for each vendor's application on top of an already widlly expensive wheel.
I see nothing in your experiment to suggest that rim "roll" contributes to the rubbing brake phenomenon. All I see is a very laterally stiff rim deflecting one direction at the ground and opposite at the pads, precisely because the rim is so laterally stiff (and the spokes go elastic). This has been explained ad nauseam in various other technical outlets. IF the rim was truly experiencing "roll," the rim would roll to the same side all the way around its circumference, like a tubular tire inflated off of a rim. The reason a shallow aluminum rim with a fairing might not exhibit the same reactionary deflection (at the pads) is because, assuming same hub and spokes, it is LESS laterally stiff. Therefore the rim deflects locally at the ground more. The rim bends overall like a potato chip.. A stiffer rim would do a better job staying on the same plane.
Hey there! I believe that Bill is telling us exactly what you explained above. The displacement of the outer edge of the wheel is due to stiff rim and not so stiff spokes. The thing is that some writer at Velonews got that video totally wrong! I guess you came here from this article: www.velonews.com/2018/08/from-the-mag/deep-wheels-an-engineering-feat-that-goes-beyond-aero_474617 See how the writer has a similar picture to that on 2:00 but he has redrawn the arrows as to support his wrong theory? The thing is that one should carefully balance the stiffness of the rim and the spokes. Too stiff rim with very soft (thin, low count) spokes is not a good idea. I really hope for a comment of mr Bill Mould on this article.
Very intresting, ive rode many carbon wheelset and they feel great because of the lightness however there has always been something about them that has always made them feel flexy, as a heavier rider. This may very well explain my preference towards alloy wheels. Thank you bill!
Thank you. Would never have figured this out myself!
Nice design of experiment and execution.
I didn’t know why rear wheel that seldom experiencing a side load is chosen as an example (L/R asymmetrical spoke tension) . Should front wheel be taken in the experiment instead? A wheel that frequently experiencing side load? (Symmetrical tensioning)
Great video. At 6:56, wouldn’t you say it would be more appropriate to have 2 lines originating from the hub and ending at the spoke anchors? The spokes at the top half and bottom half seem to be at different angles. For example, I think the lower half of the spokes are at a 3.1% angle.
I also have a hypothesis that deeper rims lead to more deflection at the bottom end between the spoke anchor point and the bead seat. Could you do this experiment with an alloy rim and see how much deflection there is between the spoke anchor “hinge point” and bead seat?
That might be a good experiment for he future. I'm quite sure that the deflection would be much less.
How about quality carbon rims? How do they perform in the same test? Interesting stuff! I just ordered my Yoeleo 50 mm wheels and have very little clearance in my bike frame with the 40 mm tires that I am using, so we'll see how that turns out :) Thanks for the insightful video!
The quality rims would deflect the same assuming they are the same depth.
Outstanding explanation, thank you very much!
Interesting video! Did you test a shallow section wheel? That would help to validate the "hinging" theory.
So, putting the breaks on under the bottom bracket is a good thing?
Dave, maybe it is, but then you get more rain and crud being thrown up into the brakes. A better solution is deep section rims that are designed to flex less. My guess is that they will inevitably be heavier, though.
6:12 wow that's a lot more than I imagined
Great video! Not that it matters a lot, but I think you made a small error in calculating the slope for the inner section. That should be (-7.21 - 3.83) / (622 - 2 * 85) = -2.4% instead of -4.2% I guess.
Ben, thanks. Maybe so, but as you said, it really doesn't change the result. I had seen the effects of this kind of rim deflection before, but I really didn't understand it until I did the experiment.
Interesting. This looks to me like another reason disc brakes could be desirable, at least on deep-section aerodynamic wheels: being part of the hub (as opposed to the rim) they would experience no flex whatsoever from the lateral forces described in the video.
While the performance of having longer spokes with an aerodynamic fairing seem beneficial, the act of truing wheels with deeply recessed nipples must be a huge pain in the ass, not least of all because doing so would require custom-built tools for each vendor's application on top of an already widlly expensive wheel.
disc brakes introduce a host of new headaches. that is the reason radially spoked wheels have disappeared with db wheels .
EXCELLENT
I see nothing in your experiment to suggest that rim "roll" contributes to the rubbing brake phenomenon. All I see is a very laterally stiff rim deflecting one direction at the ground and opposite at the pads, precisely because the rim is so laterally stiff (and the spokes go elastic). This has been explained ad nauseam in various other technical outlets. IF the rim was truly experiencing "roll," the rim would roll to the same side all the way around its circumference, like a tubular tire inflated off of a rim.
The reason a shallow aluminum rim with a fairing might not exhibit the same reactionary deflection (at the pads) is because, assuming same hub and spokes, it is LESS laterally stiff. Therefore the rim deflects locally at the ground more. The rim bends overall like a potato chip.. A stiffer rim would do a better job staying on the same plane.
Hmm... you got a good point!
Hey there! I believe that Bill is telling us exactly what you explained above. The displacement of the outer edge of the wheel is due to stiff rim and not so stiff spokes.
The thing is that some writer at Velonews got that video totally wrong! I guess you came here from this article: www.velonews.com/2018/08/from-the-mag/deep-wheels-an-engineering-feat-that-goes-beyond-aero_474617
See how the writer has a similar picture to that on 2:00 but he has redrawn the arrows as to support his wrong theory?
The thing is that one should carefully balance the stiffness of the rim and the spokes. Too stiff rim with very soft (thin, low count) spokes is not a good idea.
I really hope for a comment of mr Bill Mould on this article.