I think that that what Heine calls "planing" is very poorly-understood, but that there's something to it.

As far as Heine's own studies on the matter go, he did a double-blind frame flex experiment. With only 3 participants, the results are not generalizable to the cycling population, but there was clearly something happening.

Beyond Heine's testing, I'm not aware of any published data on the matter of how frame flex affects pedaling. But, Cannondale's Damon Rinard indicated that he saw something similar.


I do have a bike that doesn't pedal very well for me. It's a traditional road touring frame, stiffened up quite a bit in the upper part of the double-diamond to be stable with rear loads. And for what it's worth, that's pretty much exactly what Heine recommends against for "planing."



At high intensities, I just can't seem to get good performance from my legs. My quads will be burning well before my lungs are straining very hard.

I think my other bikes mostly pedal pretty well for me. They don't all pedal the same, but they pedal well.

Interesting article, thanks for posting. I don't know about the claims in the article, but I have a first gen Cervelo S3 road bike that is definitely too stiff for me. Beautiful bike, but not much of a joy to ride unless the road surface is glass. My experience with that bike has always made me snicker a bit at manufacturers tripping over themselves to claim their bike is STIFFER!!

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Dimond Bikes Superfan

I'm guessing that "planing" describes that sensation of your pedal rate being in synch with the flex of the frame, rather than at a different frequency. Could be very wrong though.


Personal thoughts: Stiffness or flex isn't the issue, it's hysteresis, i.e. absorption of the energy put in and released by flexing, rather than it being efficiently returned to the output.

One more thing though, from that series, I wish every bike user and light manufacturer would read this:
https://janheine.wordpress.com/...make-a-better-light/

Heine has better skills at marketing than in running careful experiments.

I said to Phil White that same comment; but that if he put the rear stays of the R series onto the S Series it would be a better ride.
The original design was a monostay and quite a jackhammer to ride. I bought an R3 despite really wanting the 'aero' road bike.
Voila, my dream came true and now I have the best of both worlds in my 2014 S3 - aero for my slow ass but comfort for my fat ass

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Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

ouch.
tru dat

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Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

"On the stiffer bikes, our legs hurt, but we never reached our maximum heart rate. On the more flexible bikes, our legs didn’t hurt, but we were completely out of breath when we reached the top after putting out significantly more power on the climb."

Legs hurt but never reached max HR?! Did they try a smaller gear? I suspect the flexy frame was the one they were accustomed to.

The flexible frame will move away from the force, which I guess means a lower peak force but longer duration for the same power output. Some people like oval rings for modifying the force-speed curve, and that seems like a better approach. Frame flex is going to involve some hysteresis losses, and absolutely sucks when going down hill.

I have the same bike, 09/10 S3, which is absolutely a keeper for me, she’s always whispering “you know you can shift up another gear”. We have zero glasslike roads here, but for me, this bike glides and flies.
Thereby reinforcing the possibility that it’s a very personal thing as to what might work for you

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'to give anything less than the best is to sacrifice the gift'...Pre

On another page/ he mentions being in the right gear can help in being tune with the rebound of the bike. I think that or there was another page where he mentioned how inefficient cogs 11-13 are resistance wise - that I definitely feel. I seldom use 11-13 and when I do the chain and teeth are so close together that I can feel the individual chain links. He said that larger rollers on the derailleur helps with that.

Elsewhere he mentions the oval chain wheels and how trail impacts downhill.

It's a lot to take in, if there is something to a bike frame rebounding with the pedal stroke and "elongating" each pedal stroke if you are in the right gear.

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Indoor Triathlete - I thought I was right, until I realized I was wrong.

I know. The experiment won't convince many. His years on the bike has me wondering, along with bike manufacturers claiming that that their bikes are better tuned, AND THIS experiment/illustration.

https://www.globalcyclingnetwork.com/...er-on-a-stiffer-bike

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Indoor Triathlete - I thought I was right, until I realized I was wrong.

This makes sense physics-wise but i'm curious as to the best way to act on it. Do you just have to try different bikes and get lucky? I'm assuming you could talk to the frame builder if you were going to get a custom frame, and this might be something they have a view on.

But i think my Speedvagen CX bike is still a few years off unfortunately :D

BQ's experiments are fairly coarse and don't do a great job isolating factors. And Heine's opinions obviously bleed through into the analysis.

But BQ's big-picture style of experiment can be useful at identifying things worth looking into. I feel like that can be relevant in a place like the cycling industry, where traditions are so strongly propped up by momentum.
It's not terribly useful if you're trying to optimize to the last watt. But they've been pretty early to the party on some things, i.e. their data indicated that tire inflation was relevant to suspension performance on road bikes all the way back in 2006.


I've tried consciously pushing myself toward higher self-selected cadence on my Campeur, and it just feels like the legs are having a harder time really connecting with the drivetrain. Even at cadences which don't feel bad on my other bikes.

I don't see that the flexing frame is providing any "benefit" that oval rings wouldn't do better.

If your legs are "sore" on a climb but you aren't breathing hard, then isn't a lower gear an obvious choice? IME my breathing is always maxed out, so the situation seems contrived.

Heine spoke about suspension losses and was an early advocate of fat tires on road bikes, but that doesn't make him a genius about everything... ;)

You also live at 7,300' elevation.

This whole flex thing was solved many years ago. That's why we're all still riding Teledyne Titans and Vitus 979s.

;) True, but it was also the case when I lived on Kauai. If my breathing isn't maxed out then I'm not going as hard as I could. Is this not normal?

Your scenario is not what Heine describes, he describes "sore" legs while not breathing hard. This is a sensation that I have experienced, more often at lower altitudes. Typically it's a result of too big a gear (as you point out), underfueling, soreness from a prior workout, inadequate warmup, or (in fewer cases) extreme fatigue or lack of sleep. Or any combination of these things.

In other words, many people's legs hurt when they're nowhere near going as hard as they could. A different frame or chainrings is not the primary solution to the factors that cause this.

Put me in the category of this is nonsense. If the effect does occur, it is negated by the energy put into flexing the frame - even if you get 100% of the energy out of the "push back" which you would not.

I don't believe that stiffness is as important as many people have believed but I certainly don't believe flexibility in a frame magically gives you 12% more power. If it did, we would routinely see 30 watt differences between pedal power meters and hub meters and consider it normal because it means we have to be losing that power into the stiff frame compared to the flexible frame. (And we all ride too-stiff frames compared to what he was testing). Conservation of energy demands that be true. Extra energy can't just come from nowhere. Lost energy has to go somewhere.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

Your conjecture isn't correct. Heine isn't claiming the 12% is lost between the pedal and wheel on a stiff bike, but that his legs feel better on the flexy frame, allowing him to produce more power. It's a purely physiological effect.

He also says more power while breathing noticeably easier. Which means more power with less metabolic input.

That must mean one of 2 things:

1: a dramatic improvement in metabolic efficiency caused by a subtle external mechanic interface (seems impossible)

2: the bike is providing more power to his pedal stroke.

Where else could the energy come from?

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

This author might have done some good tests, but also seem to have a strong tendency to present assumptions as facts, backed up by an unrelated test. The scientific rigor behind his articles are severely lacking.


Statement: "Once we got in sync with the frame"..." frame that is too stiff apparently ‘pushes back’ against the rider’s pedaling. "
Me: What does this really mean? What does it mean to be in sync with the frame? And of course a frame "pushes back" against the rider's pedaling. That's how a bike moves forward... Did the rider ride uphill in the biggest ring possible where he struggled to turn the crank? Was he in the same gearing on both bikes? Would this problem go away if he used a higher cadence / lower gear?

Statement: "Our tests indicate that more powerful riders may benefit from (slightly) stiffer frames. It all depends on your pedal stroke and power output."...
Me. Not sure how the test indicated this... sounds like an assumption

Different article on frame statement from website states: "In recent years, it has become clear that many riders perform better on flexible frames".
Me: It has become clear? I clearly missed the memo

Different article on aerodynamics: "Bicycle Quarterly did extensive wind tunnel research on the aerodynamics of real-world bicycles."
Me: Where's the data?

Different article on why flexible forks are better: "Even a flexible wheel corners just fine – I haven’t heard anybody talk about the poor handling of aerodynamic wheels with few spokes (and low lateral stiffness)"
Me: OK. any data? no, so flexible is better because the author hasn't heard anyone complain about wheel stiffness (not talking about whether they are complaining about the right thing).

Same article on why flexible forks are better: "At low speeds, the front wheel turns at a greater angle, which puts small lateral loads on the fork... At high speeds, as in the top photo, the fork turns very little even when you corner hard, so the flex is insignificant"
Me: I thought fork flex is related to lateral force (centripetal force required to turn, with a formula of m*v^2/r). That would mean you can apply a lot of lateral force to your wheel even if you are not turning your fork by much.

Also, I think this author does not share my obsession with bike weight "the best fenders don’t weigh much.... weigh between 423 and 540 g"
Me.... that's half of the frame's weight....

He breathes easier on the *stiff* frame. Obviously, because he is putting out 12% less power! As I mentioned earlier, he is in the wrong gear on the stiffer bike. I don't understand what they were trying to control, but it sounds like some subjective feeling in the legs (with gearing fixed!) rather than a maximum effort.

I suppose a "good" test would be for group of cyclists to swap back and forth between stiff and flexy frames, and ride an uphill TT like they really want to win. Record power, HR, cadence, and subjective impressions.

Heine isn't claiming a change in metabolic efficiency, he's claiming a difference to how effectively the legs are able to supply force. The description of cardiovascular load dropping at lower powers is consistent with metabolic efficiency staying the same.


I'll have to look back at the study later, I don't remember gearing being held constant but it's been a while since I read it.
As I indicated above, when I'm on my Campeur, going to a lower gear doesn't seem to fix the problem. It feels like my ability to supply torque drops precipitously.

I am kind of with you. What do we do with this information, if true? He is saying that a flexible bike might flex back at the right time if the the person is in the right gear.

First of all, being in the right gear is key to feel. After that, riders vary so much by size and weight that are we getting into what's a good frame for someone below 150lbs, between 150-175lbs, 175-200lbs and then over 200lbs. Or maybe a better measurement might be watts for a short period of time.

I find it hard to work with the idea that Jan posits.

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Indoor Triathlete - I thought I was right, until I realized I was wrong.