Well, there you have the better of me! Checkmate. I'm outahere. :D

A link to my subjective experience? I've related it to you. I can't put you in my body.

If I'm wrong then I'm wrong. I'm OK with that.

With a pedal-based power meter, a PowerTap wheel, and a bunch of frames, we could find out whether this is true, and how big a deal it is if so.

This is a family forum. :mad:

Not necessarily. In the podcast I linked to...they theorized after their testing that it seemed likely flexible bikes can create a sort of ergonomic gain for certain people.

edit: It's already been done. On one frame anyway. Guy couldn't find any difference between power at crank and power at hub. minute 14 in this podcast: https://cyclingtips.com/2017/06/cycl...ffness-matter/

In tennis,

lower level players use lighter, more flexible (CF) racquets, that generate substantially more ball speed

than the stiffer, heavier ones used by top players. They ( the top players) have plenty of power, & need more control.

This is true, and would be a relatively simple test.
Yet I have never seen data from such a test. Manufacturers are quick to say that frame X is stiffer than frame Y but have never seen data that it will save you some Watts and takes less effort to achieve the same result.
Road tests are also quick to say how well a bike accelerates or transfers power but again I have never seen data.
I am referring to efficiency of power transfer here, not because of weight or aero properties.

Not really.

No. That doesn't seem to have been a particularly common failure even in the era of noodly frames though.

Yes, although it's minimal for me. Currently all of my wheels have shallow aluminum rims (even on my modern bikes) which is an area where noodliness actually helps to prevent rub; the flexy rims don't transmit deflection at the contact patch to the opposite side of the wheel. Where rub seems to be seen really often is with deeper-section wheels that aren't laterally braced well by he spokes.

Obviously frame stiffness should have some impact as well, although that's a bit hard for me to quantify; I never experience any brake rub on my noodliest frames. But that might just be because they're fitted with older brakes that I find it hard to adjust as tight to the rim.

Yes.

An interesting question would be whether a stiff downtube and chainstays could prevent it on an otherwise flexy frame. If someone desired some amount of torsional flex, perhaps that could allow it while preventing significant changes to shift cable travel length. Heine seems to think that approach has merit...

E-shifting probably also solves the problem.

I don't think frame stiffness matters much at all in that regard. I know it's commonly held that it does; try the higher-end bike at a bike shop, enjoy how punchy the bike is and how tightly it holds itself together as you throw it back and forth out of the saddle, the salesperson will explain that that's what frame stiffness feels like.

The thing is, it's also what light weight and low-ish trail feels like, features that are also typical of quality racing bikes.

My gravel bike - a drop bar conversion of an '83 Stumpjumper and probably the stiffest of my vintage steel collection despite the long wheelbase (due to being braced and beefed up) - is by far my wobbliest bike when hammering out of the saddle at low speed. The harder I pedal, the harder it is to keep the front end tracking straight.
But that's because the harder I pedal, the more I toss the bike to the side. Being an MTB frameset, the trail is high, and the contact patch has lots of torque on the steering axis. So the steering axis rotates aggressively when the bike is rocked, and because the wheels are heavy, there's more mass to fight.
Amusingly, the high trail also makes the bike stiffen up with speed. By 25mph, it's hard to make it not track straight.

Meanwhile, my 1983 Miyata 710 has a front end so flexy that I've freaked out an LBS mechanic before by leaning on the handlebars, and being a midrange vintage steel bike, it's not like the frame triangles are all that stiff either. But it feels nearly as confident, consistent, and tight out of the saddle as my Emonda does.

I don't take that very seriously as a metric when dealing with things that are messy to measure, especially in cases like this where I suspect it's easy to conflate with unrelated things.

Especially especially when it's hard to isolate from other desirables (like weight) due to what's available.

If it's not throwing oil or grease all over me and my bike, I don't worry with mine. If I happen to have a rag in my hand when I am realizing there is muck all over it, I might wipe it off.:)

Obviously my weak trolling attempt has failed. Unless you're doing like a double blind meta-troll of some sort, in which case I feel foolish :o

I wax my chain anyway haha ;)

Failed.... I thought I was participating in propagating it. But a few minutes went by and no one else jumped on. :thumb:

Based on the crowd here, it may well still work regardless. Here's hoping :roflmao2:

I agree. All of these companies have the resources to test this. Cervelo says their new tube shape saves 8 watts from air resistance, and is 14 % stiffer; if that stiffer got you some measurable speed increase, they'd say it.

I don't doubt that some people do better or worse on different gear. But how would a set of meters that measure at the pedal (what you put into the bike) and hub (what makes it to the wheel) not show the difference we're talking about here? The claim is a stiffer bike puts more power into forward motion. That should be easy to test objectively. If it's true, we should be talking about classes of stiffness like we do with different rim depth categories.

It was just one frame, trying to detect any power lost to frame flex at all, not a comparison of frames. I assume they made an adjustment to accojnt for powertrain losses.

Largely has to do with the sampling rate of a power meter to create an average power per unit time aka per second. If a higher average power sampling were taken, the algorithm with a power meter would have to be more sophisticated to interpolate the change in stain due to power change. At a cadence of 90 RPM, this would mean 1.5 revolutions of the crank per second and likely differential power recorded between PM on the crank and PM on rear wheel would be missed. So the difference between BB and rear wheel is probably mostly how a PM reports power. That coupled with likely very little power loss anyway.


So much can and has been written on the subject of stiffness and power transfer and I believe Abe is right that it is perhaps one of the more beguiling conversations and not perfectly understood, in part because there is no right answer. Idealized stiffness and where to put it in a frame varies based upon rider strength. Just like some may feel a carbon handlebar is whimpy when sprinting and I don't. A 1500 watt sprinter can pretzel a given handlebar and I can't flex it. The stiffness equation can of course elude custom frame makers sitting down with their customers and of course big bike brand manufacturers change stiffness...move it around on pretty much every model change which suggests they are searching as more is learned with the passage of time as technology advances. Specialized which is a heavy R&D company is a notable example with the evolution of both their Tarmac and Roubaix. Every model was either slightly or dramatically changed in flex and frames ended up looking nothing alike model to model every 2-3 years apart.
Just like the past 5 years was a watershed for Al as lessons were learned about carbon which were applied to Al because Al could be formed like molded carbon, I believe the next 5-10 years will continue to be further refinement for carbon and Al as more is learned about stiffness. Steel and Ti are of course more constrained by inability to change frame section shapes due to limiting manufacturing practices and of course weight constrains stiffness of steel compared to lighter carbon because a frame as stiff as carbon made of steel would be much heavier.


The podcast...thanks to Abe for the reference, was perhaps one of the best discussions I have heard or read about stiffness. It buttresses in fact what many of us know intuitively as many of us have owned that bike which just seems to create more effortless speed than others. And it may not be the stiffest bike just like in the test.


When the Specialized SL2 Tarmac came out, professional riders clamored for a stiffer bike. So Spesh released the SL3 which rode like a cattle truck and pros loved the speed of the bike but hated the ride quality. Then Spesh decoupled stiffness and created the SL4 which was much more vertically compliant but if anything was more laterally stiff. This was a period when leaps were starting to be made with differential section modulus and frame design was really starting to improve....not very long ago either. The podcast said the SL4 Tarmac is one of the stiffest frames ever created...and yet it had now a good ride quality. Then Spesh came out with the 'rider first' SL5...a slogan that suggested greater parity was created throughout different frame sizes. This is when working with McClaren they strain gauged a bunch of different frames and studied what riders of different sizes preferred. What did Spesh do? They softened the flex for the SL5 compared to the SL4. And now there is the new aero SL6 just coming out which no doubt will be preferred overall as further refinement is achieved in the stiffness equation.


The podcast revealed that mfr's now based upon data mining and continuous testing coupled with computer modeling, maybe zoning in on an idealized bottom bracket stiffness....a sweetspot...not too stiff, but not too soft.
Cannondale has identified a number for this force/deflection as a target.


Take away from the podcast is...because pedal stroke force isn't linear...there is a power zone when force is higher as the foot crests over the crank center and pushes down, a bike has a pulse or a resonance. And of course most objects based upon their moment of inertia have a resonant frequency. There maybe a relationship between stored and applied energy that can be used as a synergy to propel a bicycle. This was implied in the pod cast and why the less stiff bike was faster for some strong amateur riders tested...which belies the stiffer is better mantra. The problem for mfr's is where to place this sweetspot which maybe be different for Peter Sagan than it is for me with probably less than 1/2 his power. Stiffness is based upon force. An object doesn't deflect without a force and a large force will deflect an object more. So an idealized stiffness is most likely different for different riders which creates a great challenge for mfr's which perhaps contributes to what some believe that stiffness doesn't affect speed. To them based upon their experience, it doesn't. But to a pro who cruises at 300 watts based upon a given frame stiffness sold to the public, stiffness may matter because they flex a frame more than the average rider.


My further thoughts.

I have a Spooky Skeletor and I love it. They don't make this model anymore but they make others.

In the past I had a custom Tsunami (small builder from AZ). Also a great bike. Mine was stolen though :(.

Good luck!