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  1. #51
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    Quote Originally Posted by ibericb View Post
    The determination that a frame's lateral flex does not lead to power loss is not new. (...)

    Quoting from that report:
    "For all pedal force deflection curves which go through zero at the deflection extremities, any energy which is lost in frame deformation at a particular instant is subsequently recovered fully in the form of propulsive energy, since the instantaneous spring energy, and therefore the cumulative energy lost in propulsion, returns to zero at every half cycle of the rider's force deflection curve. The only qualifications to this conclusion arise from conditions previously stated, specifically:

    • that the forces between rider and bike are as shown in Figure 2c

    • that energy lost in the form of heat in the frame material is neglected."

    This is an odd discussion. I understand the conservation of energy - I have a degree in physics. The above statements are rather trivial and meaningless. If we neglect "the energy lost in the form of heat" then the "cumulative enery lost" turns to zero.

    Nobody will deny that. If there's no energy lost - meaning there's no heat produced, I assume - then there's no energy lost. But even if there's no energy lost and the flexed frame gives back all the potential energy it gained by being flexed - it doesn't tell you anything about your speed or the loss thereoff.

  2. #52
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    I sort of started this thought by mentioning chain rub earlier - but if the frame flexes enough to rub the chain on the FD cage, does that change the chain line sufficiently to introduce some inefficiency, does it put any extra load on the crank or pedal axle bearings as force is being applied in a slightly different plane, if you twist your foot on the pedal slightly does this effect the amount of downforce you can generate, can you flex the frame enough to rub the rear wheel on a brake block. I'm not sure if any of these things lead to any loss in efficiency, I guess my question or point is if frame flex itself doesn't directly cause a loss in power, can it indirectly via what I just mentioned or anything else like them?

  3. #53
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    To restate my question somewhat, even though the frame is deforming elastically, does it automatically follow that there is no loss of power to the drivetrain? If the storage of energy is happening when the chain is under high tension and the return of energy is happening when the chain is under lower tension, is the power delivered to the chain the same? This is an honest question. It may be uninformed, I will admit that, but I really am curious.

    A simple bow deforms elastically, storing and releasing the energy imparted by the person who draws the bow. However, if you've ever fired a bow you know that it continues to vibrate energetically after the arrow is launched. That energy is part of the energy stored in the bow when it was drawn, so all of the energy stored in the bow by its being drawn is returned when it is released, but not all of that energy goes into the arrow because it is released after the arrow is no longer engaged in the bow.
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  4. #54
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    In the sport of cycling I’m a relatively fit and long time cyclists, nothing more. In terms of sophisticated knowledge of all things related to cycling I am despite my experience little more than a neophyte. I represent what Nike used to sell; I “Just do it!

    The bicycle moves as a result of the force applied by the cyclist to the bike mainly through the pedal/foot interface. How much of that a specific rider conveys to the rear wheel on a specific bike is a big factor on how fast the bike moves. If the force transferred, however measured, is 95 percent that bike will move faster than if anything less than 95 percent is transferred. (All other things being equal.) What variables or conditions can cause an interference or impedance in the transfer of power along the “chain?” Many of them we know. Some we may not.

    Regarding what impact if any does the stiffness of the bottom bracket seems based upon what I read debatable or unsettled even if there is a majority or consensus opinion one way or the other on that issue.

    One thing for sure is that for optimal enjoyment and performance among the many factors the rider has to be happy with the setup. That includes from their subjective perspective the stiffness of the BB and its impact.

  5. #55
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    You seem to be treating stiffness as a single property. Stiffness where? Vertically or laterally? Everybody will like compliance vertically. Nearly everybody will like stiffness laterally. How you obtain both is the question frame builders have been working on for some time.
    Quote Originally Posted by Pirx View Post
    That test has been done, with some 1983 steel steed (Pinarello) versus a modern carbon bike (2009 Lapierre). Result, in a nutshell: No difference.



    The difference was all in your head, at least the difference caused by increased stiffness. Stiffness has no measurable effect on acceleration, and no effect on average speed. Your Cervelo is lighter, hence the better acceleration, and much more aerodynamic, thus higher average speed. Nothing to do with stiffness.

  6. #56
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    Quote Originally Posted by ibericb View Post
    There is a very important caveat to note, that is well explained in that report, and that is the elastic return of propulsive force is dependent upon the force applied to the cranks vs. crank position (the first qualification noted above). That result is predicated upon zero force application with the pedals in their 12 and 6 o'clock positions. That is the fairly normal and typical seated force profile, or very near it. A departure from the efficient return of propulsive force would be expected when the rider applies appreciable force when the pedals are near vertical. That might typically be expected in an out-of-saddle extreme pedal force situation, such as climbing or sprinting. In those situations then some small fraction of the force applied by the rider to the pedals at those positions should be expected to be lost by spring work being done directly on the rider himself in a way that cannot be converted into propulsive force. However, force being applied at those positions in likely from supporting the rider's weight, and would not be constructive in propulsion to any significant degree anyway.
    The point about crank position has not been discussed. Conversely to what you stated, any return force from frame flex close to pedal positions 6 or 12 o'clock would also be lost. That's because the frame unwind torque that is returned to forward motion is dependent on pedal position and force when the unwind happens, as stated above.
    This assumes that the unwind force come from the pedal offset torque on the frame.

    The work returned needs to produce crank torque, and that depends on crank angular position relative to the unwind force.

    The experiment here is to stand still balancing the bike, and weight and unweight one pedal in the 6 o'clock position - the bike will obviously not move forward. But you will be flexing the frame, doing work to flex, and getting it back when you unweight.

    Not saying stiffness makes a difference, or not. But different pedal strokes, or even cadence, may be a factor.

  7. #57
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    Many years ago (mid-80's I guess), when I was actively racing, I was on a training ride with the team I raced for. We were riding up Ute Pass out of Colorado Springs. I was riding a fairly inexpensive 25" (63cm) Fuji steel racing bike(don't recall the specifics). At one point, during a particularly steep part, I was up out of the saddle, the coach, who had been riding behind me, pulls up to my side and started talking about frame flex. I'm 6' 5" and in those days was a pretty powerful rider As he was talking about the subject, I looked down and realized just how much the entire frame was twisting as I torqued back and forth on the handlebars.

    Later, as a demonstration of how much energy goes into actually flexing a bike frame, he put the bike in a trainer stand and had me stand on the pedals and attempt to flex the frame the same way I was flexing it as I was riding up the pass. It's really hard work to bend a bike frame.

    Consider how many pedal strokes it took me to climb up that pass. Imagine standing over the bike in your trainer and just manually flexing it the same amount that many times.

    It may be difficult, or even impossible to quantify lost energy to flexing a frame, there is no doubt that it happens. More importantly though, is that this flexing, however small it may be, is repeated hundreds or thousands of times per ride.

  8. #58
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    Quote Originally Posted by ibericb View Post
    There are a couple of companion BQ blog posts that came late last year that help explain long-debated issue of frame flexibility, power transfered, performance, and importantly overall rider perception. They can be found here (November 2014), and here (December 2014).

    As one well schooled in physics I wrestled with this in my own mind for years. In the second of those links (December 2014) the blog authors note a series of finite element analysis simulations which found that the work done to flex the frame during pedaling is returned to the drivetrain on the return (spring rebound). If the finite element analysis simulations run for BQ's work are representative and valid, then they resolve a big part of the question. Yes the frame flexes, so how much power is lost between the pedals and wheels as a result of that frame flex? The answer is very, very little. The remaining source of power lost would be the hysterical loss between material deformation and rebound. For the rigid materials typically used in bike frames, and the small elastic deflections that would be rational, that loss is probably negligible. So, from a purely physical look it appears that frame flexibility is, in fact, not a source of power losses.

    The great debate over power loss and frame flexibility seems to revolve mostly around differences in perceptions between different riders. Part of that is possibly due to a difference in perceived effort between frames of different stiffness. That perception is grounded in the resistance the rider experiences when he applies force to the pedals (it's in their legs, not their head). It extends then to apparent acceleration. If the BQ test results are representative, a rider should be able to develop more power on the more flexible frame. I suspect, however, this has a limitation, and that for any given rider there is an optimum flexibility that facilitates the optimal development of sustained power output for that rider. Regardless, the impact of frame flexibility on a rider's ability to develop power complicates the issue, as it focuses on the rider's ability rather than the original question of applied power lost to work being done to flex the frame back and forth.

    The BQ work makes a key point, which I believe is understated. At the end of the day it's about the total performance of bike + rider that matters most. That includes a riders ability to develop power as well as the bikes response to that input. Both of those will probably vary between different riders as well as riders with different objectives at varied times.

    thanks for the links for the 2 articles. very enlightening and interesting read regarding frame flex.

    One question I'm wondering about "planing". Since it is such a tuned process requiring the flexibility of the frame to match the power output of the rider, then it would be difficult for a person to go buy a frame that is optimized for him, right. Because the buyer and builder would need to spend time testing out different frames together, in an environment where there is a means to measure power output.

  9. #59
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    Quote Originally Posted by Z'mer View Post
    The point about crank position has not been discussed.
    Um, I thought that's what I did - discuss the importance of pedal position for recovering the energy stored in the frame as propulsive power.

    Conversely to what you stated, any return force from frame flex close to pedal positions 6 or 12 o'clock would also be lost. That's because the frame unwind torque that is returned to forward motion is dependent on pedal position and force when the unwind happens, as stated above.
    This assumes that the unwind force come from the pedal offset torque on the frame.

    The work returned needs to produce crank torque, and that depends on crank angular position relative to the unwind force.

    The experiment here is to stand still balancing the bike, and weight and unweight one pedal in the 6 o'clock position - the bike will obviously not move forward. But you will be flexing the frame, doing work to flex, and getting it back when you unweight.

    Not saying stiffness makes a difference, or not. But different pedal strokes, or even cadence, may be a factor.
    Not conversely at all, it is what I stated, or at least tried to. Did you actually really read the comment you quoted ? Your thought experiment description is, however, a nice way of illustrating the point, so I do appreciate that.



    Quote Originally Posted by Migen21 View Post
    Many years ago (mid-80's I guess), when I was actively racing, I was on a training ride with the team I raced for. We were riding up Ute Pass out of Colorado Springs. I was riding a fairly inexpensive 25" (63cm) Fuji steel racing bike(don't recall the specifics). At one point, during a particularly steep part, I was up out of the saddle, the coach, who had been riding behind me, pulls up to my side and started talking about frame flex. I'm 6' 5" and in those days was a pretty powerful rider As he was talking about the subject, I looked down and realized just how much the entire frame was twisting as I torqued back and forth on the handlebars. ...
    While I have no doubt you moved the frame by a significant amount, that movement and the attendant force required doesn't necessarily equate to a loss of propulsive force being transfered to power at the rear wheel, but it could, and that's the point.

    Consider the weighting the pedal in the 6 o'clock position with the right foot, bike leaned well to the left for balance, the bottom bracket is flexed well to the left. Now ask yourself did you lose power to turn the crank in doing that? How much of the force being supplied by your weight at the 6 o'clock position is used to turn the crank? I suspect not much at all. If it were in fact zero you haven't lost any power in moving the frame back and forth, rather the frame is supporting your weight, as it does anyway in a pure vertical load, but now that load is a combination of vertical and lateral loads.

    The point is the frame flexing laterally is no more a sign of power lost than the frame flexing vertically.

    If, however, when lateral frame flex is a result of force being applied to the pedals to turn the crank, which can come from your weight as when you first stand on the pedals as they move between 12 and 3 o'clock (as viewed form the right side), then power could be lost if, when the frame returns as that phase of the power cycle moves past peak, the foot and pedal are not in a position to translate that return spring movement into crank rotation (e.g., 6 o'clock). This is where the interaction of the rider and bike comes into play, and rider technique becomes a key factor in determining efficiency in force to power conversion.

    It may be difficult, or even impossible to quantify lost energy to flexing a frame, there is no doubt that it happens. More importantly though, is that this flexing, however small it may be, is repeated hundreds or thousands of times per ride.
    It's not difficult to determine how much work it takes to move the frame a fixed amount. But moving the frame doesn't necessarily equate to power lost in propelling the bike forward. When you sit on the bike in a pure vertical orientation the frame flexes vertically. When you lean the bike one way or the other the frame also flexes laterally. In neither case does that flex from a weight load (a force) indicate a loss of propulsive power.
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  10. #60
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    Quote Originally Posted by aclinjury View Post
    ...
    One question I'm wondering about "planing". Since it is such a tuned process requiring the flexibility of the frame to match the power output of the rider, then it would be difficult for a person to go buy a frame that is optimized for him, right. Because the buyer and builder would need to spend time testing out different frames together, in an environment where there is a means to measure power output.
    If you could pin down for what regime you would want to optimize a frame for force-to-power conversion alone, then I guess it could be done, but it would probably be a series of experiments. The broader problem is what regime to optimize for - steady state seated on the flats, climbing, standing sprints, ... ? As I understand it the key variable is the power development cycle vs. pedal position, and attendant foot/pedal position when the frame rebounds. So pick the pedal force cycle you want to optimize for. Appreciate that you would probably be compromising other performance elements if you heavily weight on just the force-to-power conversion aspect.

    The more practical approach is to choose a bike by trials across a representative range for your intended use, and figure out what works best for you reasonably broadly in that riding situation. That could lead to different preferences or bikes for nominal road conditions vs. heavy climbing vs. crtis vs. ...
    Last edited by ibericb; 09-15-2015 at 02:24 AM.
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  11. #61
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    Quote Originally Posted by ibericb View Post
    I spent over 40 years of my life designing and doing scientific experiments in research labs. I've written and reviewed hundreds of published peer reviewed research papers, grant proposals, etc. I have yet to see even a single experiment that controls ALL of the variables in a complex system. That doesn't make the work or attendant conclusions any less valid, so long as it is recorded and reported accurately.

    When you have some real measurable results to present, or can provide another source with at least comparable design and control, then please bring it. Until then your attempt to dismiss some reasonable work is nothing more than ungrounded drivel.
    Well, there you go. I say "crap".... You say " drivel". I guess we are even...enjoy your mental masturbation exercise. My only point was that as pirx says, there doesn't seem to be any science supporting the contention........except of course the "science" you have presented on "planing". Cervelo instrumented bikes and tried to determine what characteristics and direction of stiffness resulted in better " feel". That's about as "scientific" as it gets. But of course, via your appeal to your authority, only your opinions are correct.

  12. #62
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    Quote Originally Posted by goodboyr View Post
    Well, there you go. I say "crap".... You say " drivel". I guess we are even...enjoy your mental masturbation exercise. My only point was that as pirx says, there doesn't seem to be any science supporting the contention........except of course the "science" you have presented on "planing". Cervelo instrumented bikes and tried to determine what characteristics and direction of stiffness resulted in better " feel". That's about as "scientific" as it gets. But of course, via your appeal to your authority, only your opinions are correct.
    All of that, and still you bring absolutely nothing, except more drivel.

    Maybe you should actually read through the thread, and note the link to research done 41 years ago by Calspan. Have a nice day.
    Last edited by ibericb; 09-15-2015 at 04:22 AM.
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  13. #63
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    You missed my point. I am agreeing with the OP on this. But the specific point I am making is that the experiment you presented with the link to the "planing" discussion should not be used as absolute proof you are correct and all others are wrong. I know you like to post links to papers that support your position.....good for you. But this is a discussion forum, and there are many points of view. I'm sure that there are a bunch of people out there who have opinions on this, want to join in the discussion, but turn away when you come on board, and declare all others to be wrong. Ride safe, the weather is still nice out there in the real world away from this forum.

  14. #64
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    Don't recall that I declared anyone wrong. I just asked for you to bring something of merit. That seems to elude you.

    BTW - if you actually read all the posts previously made, including the sources provided by both the OP and me, you would appreciate that the "experiment I presented" as you like to refer to it (I didn't present it, Jan Heine did) is the exact same experiment that was cited in the blog entry the OP pointed to. The blog entries I provided were merely updates by the same authors, referencing the same research they did in 2008, as well as the previous blog entry the OP pointed to. So if you agree with the OP's points, it escapes me why, pointing to the same sources and experimental findings, that you take issue with citations to which I pointed and summarized (which the OP agreed with). They are the same. One further point, the analogy to "planing" was Jan Heine's, not mine. As best I recall prior to this post I never mentioned it, not once.
    Last edited by ibericb; 09-15-2015 at 05:26 AM.
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    Quote Originally Posted by ibericb View Post
    Um, I thought that's what I did - discuss the importance of pedal position for recovering the energy stored in the frame as propulsive power.
    Sorry, meant to imply, but should have said, "was not discussed in this thread until your post", which I quoted.

  16. #66
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    Quote Originally Posted by Z'mer View Post
    Sorry, meant to imply, but should have said, "was not discussed in this thread until your post", which I quoted.
    Cool. So I take it we agree on the physics, and thier impact on power.
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  17. #67
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    Quote Originally Posted by ibericb View Post
    If, however, when lateral frame flex is a result of force being applied to the pedals to turn the crank, which can come from your weight as when you first stand on the pedals as they move between 12 and 3 o'clock (as viewed form the right side), then power could be lost if, when the frame returns as that phase of the power cycle moves past peak, the foot and pedal are not in a position to translate that return spring movement into crank rotation (e.g., 6 o'clock). This is where the interaction of the rider and bike comes into play, and rider technique becomes a key factor in determining efficiency in force to power conversion.
    This is the point I was trying to move the discussion to. You really need to start the analysis not with the frame, but with the torque at the crank.

    I think if you agree one can flex the frame at 6 and 12 o'clock, you'll agree that you can flex it at all other angles in between. But the torque generated by the rider cannot (easily) be made at all angles.

    To simplify, for vertical right pedal force only, maximum rear wheel drive torque occurs at the 3 o'clock position. Again vertical force only, zero torque is produced at 6 and 12. In between the torque follows a curve going from min to max depending on crank angle.

    So let's say some peak down force on pedals, at a certain crank angle, is lost to producing rear wheel drive torque (by flexing the frame). You will recover the lost torque when the frame unflexes only if the unflex occurs at a complimentary crank angle from the vertical axis.
    Example - peak right pedal frame flex occurs at 2 o'clock, unflex occurs at 4 o'clock. These positions have the same angle delta angle from vertical, so you recover the lost torque.

    But if peak frame flex occurs at 3 o'clock, and unflex at 5 o'clock, the delta angles from vertical are not equal, and you will lose torque to frame flex that could have gone to the rear wheel instead.

    Of course, the opposite could also happen. If you have a flexible frame, and get max frame flex at say 1 o'clock, and unflex at 4 o'clock, you will have converted the unwind flex into more drive torque than you could have made at 1 o'clock.

    With new power meters based on crank arm strain gauges, these forces versus crank angle should be easily available to see what's really going on in real world situations. Or as a minimum show differences in pedal force vs. angle between riders, or same rider under a wide range of conditions.

  18. #68
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    Quote Originally Posted by Pirx View Post
    Thus the best advice is to ride the frame you like, even if it's a more flexible one, and ignore the illiterate marketing drivel.
    yeah, I've since gotten used to having a really stiff (in the bb area) frame and like it but when I first got it I wasn't too crazy about what felt like a complete lack of flex when sprinting. I felt the lack of flex prevented my pedal stroke, when sprinting only, from following it's natural path. With a bit of flex I felt more natural and like my legs followed the path they wanted to instead of being forced into a path by the frame.

  19. #69
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    Quote Originally Posted by Jay Strongbow View Post
    yeah, I've since gotten used to having a really stiff (in the bb area) frame and like it but when I first got it I wasn't too crazy about what felt like a complete lack of flex when sprinting. I felt the lack of flex prevented my pedal stroke, when sprinting only, from following it's natural path. With a bit of flex I felt more natural and like my legs followed the path they wanted to instead of being forced into a path by the frame.
    Precisely. The optimum frame stiffness, or flex should I say, it is vastly dependent on what you do on the bike and on how you do it. The "planing" Jan Heine refers to as the outcome from his optimized lightweight steel tubing frame is also tailored and greatly dependent on his very smooth pedal stroke, his cruising cadence of 110 rpm and his climbing cadence of 95-100 rpm. That's racing territory performance and not representative of the typical rec rider output.

    Jan Heine is the first to admit in his blog discussions that a stiffer frame under him would have required him to pedal at a slower cadence in order to "guide" the frame oscillations into "planing" territory.

    This raises the question of what happens when a rider capable of sustaining a cruising cadence of only 75-85 rpm pedals Jan's lightweight steel bike? Would he be better off with a stiffer frame? Lets also make things closer to reality and say that the uniformity of his pedal stroke is not as smooth as Jan's.

    All in all, I dont think anyone likes to ride either on 2x4's or on wet noodles. Most of us tend to prefer someplace in between. The questions of effectiveness and optimum efficiency at that sweet spot could only be partially answered quantitatively. This is where the art of building a custom frame enters the science and lets the Master builders separate from the rest.

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    Quote Originally Posted by dcgriz View Post
    Precisely. The optimum frame stiffness, or flex should I say, it is vastly dependent on what you do on the bike and on how you do it...
    And frame size, your size, your power, intended use as said. Outside of you imagination of course.

  21. #71
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    Quote Originally Posted by Z'mer View Post
    This is the point I was trying to move the discussion to. You really need to start the analysis not with the frame, but with the torque at the crank. ..
    That's one way of approaching it. But it gets even more complicated.

    The biodynamics folks who study pedaling efficiency now typically use instrumented pedals that let them sort the total applied force into three directional components, only one of which is effective in rotating the crank. The other two occur laterally, one parallel to the crank arm axis, and the other normal to that same axis. The question you've focused on is how much of the effective force is translated into rotating the crank arm vs. how much goes into moving the frame laterally, and how much of that frame displacement can be recovered for propulsion based on crank and pedal position during relaxation. Where it gets even a bit more complicated is the related question, does lateral frame displacement (flexing) during the application of total force to a pedal change or alter the fraction of effective force as a share of total applied force?

    What all of this illustrates is really one of the made by the OP from the outset, and restated repeatedly through the thread, and that is when you introduce a real rider it gets complicated quickly. At the end of the day what works best for one rider may well differ from what works for another. What's leads to best performance depends on what is meant by performance, and on a host of attendant variables. Along with that the notion that a laterally stiffer frame is better for performance simply because stiffer means better translation of pedal applied force into power is not a valid general conclusion. It may work for some, but as a general principle it is misguided.
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    Quote Originally Posted by ibericb View Post
    Don't recall that I declared anyone wrong. I just asked for you to bring something of merit. That seems to elude you.

    BTW - if you actually read all the posts previously made, including the sources provided by both the OP and me, you would appreciate that the "experiment I presented" as you like to refer to it (I didn't present it, Jan Heine did) is the exact same experiment that was cited in the blog entry the OP pointed to. The blog entries I provided were merely updates by the same authors, referencing the same research they did in 2008, as well as the previous blog entry the OP pointed to. So if you agree with the OP's points, it escapes me why, pointing to the same sources and experimental findings, that you take issue with citations to which I pointed and summarized (which the OP agreed with). They are the same. One further point, the analogy to "planing" was Jan Heine's, not mine. As best I recall prior to this post I never mentioned it, not once.
    I've looked back through this thread and I agree that you haven't declared anybody wrong, so for that I apologize. I still think the Jan Heine stuff is a bit bogus, in particular the planing theory. But i agree in general with the overall point of this thread. Must have woken up on the wrong side yesterday.

  23. #73
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    Cool!

    FWIW, I don't like the planing analogy either. It's Heine's, and he uses it in his writings including a review of a Specialized Diverge in the new issue.
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  24. #74
    RoadBikeReview Member
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    Quote Originally Posted by Pirx View Post
    This is somewhat of an old topic, and I think by now many of us understand that the still ongoing obsession with frame stiffness, in the form of "lateral stiffness", "stiff bottom brackets", etc., etc., is nothing but marketing BS. Yet, just about every single article you see that presents a "review" of some new bicycle, and certainly every single manufacturer blurb about the newest bike from manufacturer X still continues perpetuating this idiocy.

    On the other hand, from the physics of bicycles it is entirely clear that frame flex, at the kind of level any halfway realistic, existing road bike will show, has almost exactly zero effect on the efficiency of "power transfer" (whatever that may mean; we note in passing that nobody ever bothers to define this term, and there is certainly not a single test or experiment of any kind that would demonstrate the relevance of this quantity). I have therefore argued for a long time that, if there is any effect of frame stiffness on performance at all, it would have to be sought in the biomechanical efficiency of the rider-bicycle system. However, a priori there is no reason to assume that this system will perform either better or worse using a stiffer frame. As a consequence, it may well be that some riders do better on more flexible frames, and some others may prefer stiffer ones. Bottom line: Nobody knows, and all the rest is nothing but clueless babble.

    The reason I am repeating the above well-known truths is that I just happened to stumble over an older post in the Bicycle Quarterly and Compass Bicycles blog, which in fact quotes a few pieces of evidence confirming what I've been saying for years. Here is a pertinent quote:



    The penultimate paragraph in that piece is also worth quoting in full:


    Amen to that.

    Here's my proposal: Can we please lay this BS of the superiority of the stiff frame to rest? Better aerodynamics, yes, lower weight, yes, these things can help increase performance. Frame stiffness? Completely and utterly irrelevant.

    I haven't read a MTB magazine for over a decade; maybe things have changed in the meantime.

    However, German 'Bike' magazine (the sister magazine of the renowed German 'Tour' magazine) did some tests in a controlled environment. This was at a time, in the 90's, when discussions were rampant of the virtues of a front suspension on a MTB vs a hardtail without suspension at all.

    Their conclusion: you will lose some energy which goes into the front suspension - rocking up and down - while riding, but you will gain back the loss going over say rough surface and your body will not become as beaten up or faitigued. So it may well be zero sum game.

    Hasn't Mavic done some blind tests with riders and a) they couldn't tell the difference between vertically less stiff wheels b) the stiffest wheel going uphill did not improve the rider's time when benchmarked against the least stiff wheel.

  25. #75
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    Assuming your peak output is at 300 oclock, the pedal system is at maximum efficiency at delivering all the energy to applying torque to the cranks.
    If the frame flexes a significant amount, it will return the energy at a different location in the revolution, when the torque of the rider is reduced to near equal to the torque of the return energy.
    But the vector result of the returning torque @ 4 or 5 oclock will mean that the output to the rear wheel has been reduced due to the inefficiency of the pedal force at the 4 or 5 oclock location.
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