For comment: "Why It's Impossible For Steel Frames To Be More Comfortable..."

[colker]

Those carbon seatposts flexing as much as shown on video are scary. A catastrophic failure there is baaad. Thank you but i rather have a traditional aluminium post.
If your saddle is in the right place and you can pedal smoothly there is no need for flex on seatposts. Sometimes the less flex you have the less energy you spend and less energy spent is comfort.
A bike saddle is not a sofa; it´s a point of balance just like the handlebar and pedals. Your body is sustained by your entire set of muscles: legs, back, abs. The more you move your muscles the more they sustain the body.

[fa63]

The opposite is also true; the more comfortable your bike is, the less energy loss towards the end of a long ride due to fatigue.

I wouldn't worry about those carbon seatposts flexing; they have been engineered to flex like that and will not break under normal circumstances.

Originally Posted by colker

Those carbon seatposts flexing as much as shown on video are scary. A catastrophic failure there is baaad. Thank you but i rather have a traditional aluminium post.
If your saddle is in the right place and you can pedal smoothly there is no need for flex on seatposts. Sometimes the less flex you have the less energy you spend and less energy spent is comfort.
A bike saddle is not a sofa; it´s a point of balance just like the handlebar and pedals. Your body is sustained by your entire set of muscles: legs, back, abs. The more you move your muscles the more they sustain the body.

[colker]

Originally Posted by fa63

..they have been engineered to flex like that and will not break under normal circumstances.

Untill they do. Like almost every bicycle part. Carbon+ lightweight+flex+seatpost+ (not me).

[colker]

Originally Posted by fa63

The opposite is also true; the more comfortable your bike is, the less energy loss towards the end of a long ride due to fatigue.

NO ever said integrated seat post Speedvagens were unbearably stiff/uncomfortable. Not even the ones made all steel.
A big saddle like the san marco regal or brooks damps a lot of noise from rough grounds but .. they are heavier. Look old. Then comes the flexy seatposts.

[martl]

Originally Posted by fa63

I wouldn't worry about those carbon seatposts flexing; they have been engineered to flex like that and will not break under normal circumstances.

I admire your faith in humanity.

[fa63]

Originally Posted by martl

I admire your faith in humanity.

I am an engineer myself, and not worried about using what I perceive to be well-engineered products (not the Chinese knock-off kinds) :-)

[vincenz]

Originally Posted by martl

Erm, no. If we define comfort in a technical way as "ability to absorb road imperfections" we of course can put numbers on it. This isn't rocket science either. It can be calculated and it can be measured. It's just physics.



The physics are the same ragardless of the parameters you name. Their dimensions vary.

You can feel a difference between the frames of different materials, but you won't feel a difference between the frame materials in terms of what amount of the road profile arrives at the riders butt and hands (contact points) because it needs to "travel" through almost all of the bicycles parts. Several of these are softer/more springy than the frame, some by a factor of 10-20. A handlebar will "flex" under a given load of 80kg in the millimeter range, most seatpost/saddle rails as well. The frame will "flex" between 0.1 and 0.3mm under the same load. It just drowns in the noise.

Erm, no. You cannot define comfort solely using ONE parameter. Unless you ride bicycles in some alternative universe that has only ONE dimension. Maybe you do. Even if you did, assigning a number to a quality doesn't tell you everything about that quality, or the material for that matter. As with the clothing analogy, you cannot assign comfort based on just stretchiness. Go ahead and wear a rubber shirt for more than a few minutes and tell me how comfortable it is compared to your cotton tees. It's just as stretchy, if not more.

I'm not sure what your bolded sentence says. Obviously you would control for all the other components other than the frame. Different frame materials will also transmit the feedback from the road differently, regardless of what the vertical deflection numbers are. A steel frame's mass and the property of the metal itself will transmit feedback much differently than a carbon frame with the same stiffness. All that accounts to the comfort equation. Defining a bike's (or a material for that matter) comfort based on one number is ridiculous. Trolled and clickbaited. I get it though, he's looking to make a living so he has to find some way to get eyeballs so he can solicit Patreon donations in the comments section.

[colker]

Originally Posted by martl

Definitely marketing. A bike frame is 11 tubes connected. If someone sees a whiff of a chance to do something a tiny bit different than the competition which does 99.9% the exact same product, they will. The bull****ters from marketing will explain the customer why "different" has to be better.
Its a common thing ever since the market changed from "lets sell this person a bike and sell him another one in 20 years from now" to "market sesearch says the average consumer is willing to fork out $$$ for a new item on average every 3 years if we give him enough incentive to lie to himself that theres a noticeable improvement (works in other fields of the hobby/consumer market as well, skis, cars, tv sets, etc. etc...)

Can you explain how any of the variations Clancy mentioned should do anything to "brake efficiency"?

Well... i happen to have one of those curved stays mountain bikes and there is significant difference.

[martl]

Originally Posted by vincenz

Erm, no. You cannot define comfort solely using ONE parameter.

Unless you ride bicycles in some alternative universe that has only ONE dimension. Maybe you do. Even if you did, assigning a number to a quality doesn't tell you everything about that quality, or the material for that matter. As with the clothing analogy, you cannot assign comfort based on just stretchiness. Go ahead and wear a rubber shirt for more than a few minutes and tell me how comfortable it is compared to your cotton tees. It's just as stretchy, if not more.

You're right, because there are 2. One is the resulting spring rate of the bicycle, the other is the damping ratio. I have no idea what you want to prove with your textile example, no one denied steel has other properties in which it is different from Aluminum, Titanium or CFK, but those other properties do not matter in this context.

When we talk about "comfort" of a bike, it can be narrowed down to: When you hit a bump of sixe x on the road, how much of that arrives at the riders contact points (spring rate) and how fast does it go away (damping ratio).

Now, Each part of a bicycle has its own set of those two parameters. The frame is one of the "hardest" springs involved, other parts have a spring rate that is c1/10th or 1/20th of that.

Hook found out that a series of springs, as we have here, can be described in the formula

1/K(resulting) = 1/K(1) +1/K(2) etc...

it shows that the springs in the compound that are the softest "dominate" the behavior of the compound. The frame is one of the hardest, so its influence is the least.

[Dino Suegiù]

Originally Posted by Clancy

If a double diamond frame cannot flex in a vertical plane then why.....

S shaped seatstays/chainstays?
Dropped seatstays?
Ultra small diameter seatstays
Specific shaped chainstays?

I’m very curious.

It is not that the "double diamond frame cannot flex in a vertical plane". It can, but the degree of flex is so small, regarding quantifiable improvement, as to be imperceptible by a rider. People claim they can feel it, and yet nobody is able to translate that feeling into measured data, even after all these years. If it remains a personal feeling, that's totally fine. A lot of our appreciation for components in this sport is purely sensual. But, it is not then any kind of universal data.

Opposite of the double-diamond bicycle frame, in our sports equipment world, are planar tools such as skis/boards/rackets/etc, where flex is paramount, and can be both measured and tuned.

Skyscrapers, bridges, aeroplanes, etc. are all designed to flex, and the degree of flex is so significant, regarding improvement, as to be extremely perceptible by an occupant. People can absolutely feel and measure it, to the degree that the data is so quantifiable that it forms a backbone of engineering building codes.

Otoh, despite endless claims both pro and con, nobody has demonstrated that a straight-legged fork is perceptibly stiffer than a curved-legged fork built to the same specifications.

So, yes, those shaped bits are really about appearance, image, marketing. They look sexy, and we know what sells. Forget even the back-end minutiae of a skinny Cervelo or English stay versus any standard old banal and mundane straight stay; has anyone really defined and measured (convincingly) the "increased performance attributes" of a Lynskey Helix frame versus a standard old banal and mundane round tubed frame?

How many frames did Dario Pegoretti build for Marco Pantani that one year, in Pantani's quest for the perfect frame? 25 or so? Not even one of those frames involved manipulating the shape of the stays, etc. And those two guys knew sexy like few others.

If someone really loves their curved stay frame, great.
But, marketing.

[vincenz]

Originally Posted by martl

You're right, because there are 2. One is the resulting spring rate of the bicycle, the other is the damping ratio. I have no idea what you want to prove with your textile example, no one denied steel has other properties in which it is different from Aluminum, Titanium or CFK, but those other properties do not matter in this context.

When we talk about "comfort" of a bike, it can be narrowed down to: When you hit a bump of sixe x on the road, how much of that arrives at the riders contact points (spring rate) and how fast does it go away (damping ratio).

Now, Each part of a bicycle has its own set of those two parameters. The frame is one of the "hardest" springs involved, other parts have a spring rate that is c1/10th or 1/20th of that.

Hook found out that a series of springs, as we have here, can be described in the formula

1/K(resulting) = 1/K(1) +1/K(2) etc...

it shows that the springs in the compound that are the softest "dominate" the behavior of the compound. The frame is one of the hardest, so its influence is the least.

OK, so why make an entire video about how comfortable a bike is using only one measurement, if not for clickbait? Assigning an OBJECTIVE number to stiffness is one thing, but then equating that to a SUBJECTIVE feeling is wrong. Not only that, but the context in which he is making that judgment with his equipment choices also doesn't cover all cases to make the blanket statement he does.

I'm not sure how you can say they have different properties, but it not mattering. Different materials at different masses would have different dampening qualities then. That should play into comfort as well, as it is compounded over a long ride. What can you say about the numbers for the damping ratio of steel versus carbon fiber frames? All I know is you would not be able to fool me with a steel vs carbon/aluminum frame comparison, all else being equal. Steel and titanium, maybe. Direct hits to road imperfections at speed will tell me right away.

[martl]

Originally Posted by vincenz

I'm not sure how you can say they have different properties, but it not mattering. Different materials at different masses would have different dampening qualities then. That should play into comfort as well, as it is compounded over a long ride. What can you say about the numbers for the damping ratio of steel versus carbon fiber frames?

I can say that they don't matter in the context of a bicycle frame for the same reason the spring rate doesn't. In order to dampen something, it has to oscillate. The frame hardly oscillates because even when you hit the mother of all potholes, it will elastic deform by a fraction of a millimeter and swing about 2-3 times. Almost all other bike parts are more significant.

[vincenz]

Originally Posted by martl

I can say that they don't matter in the context of a bicycle frame for the same reason the spring rate doesn't. In order to dampen something, it has to oscillate. The frame hardly oscillates because even when you hit the mother of all potholes, it will elastic deform by a fraction of a millimeter and swing about 2-3 times. Almost all other bike parts are more significant.

And are there no things that humans can perceive and corroborate that cannot be measured simply with a number? Using a scientific approach to make a subjective judgment is flawed.

Maybe you just are not as discerning then if you cannot tell a difference between frame materials. In that case, you can ride whatever and have it all feel the same. Kudos to that.

[Mark McM]

Originally Posted by vincenz

A bike does not only flex up and down. How do you ride your bikes? Do you "ride" them by stripping them down to the frame and stand in one plane on the top tube and exert force perfectly vertically? The truss analogy is flawed, which the entire video is based on.

Okay, maybe we need to narrow down what the video means by "comfort." Since it also talks about seat post flex, I'm pretty sure what is being addressed is comfort at the saddle. Frames can vary quite bit in flex to out-of-plane forces. But does applying large out-of-plane forces really affect comfort? I know I that "comfort" has no meaning when I apply large out-of-plane forces.

Originally Posted by vincenz

If comfort includes vertical compliance, it also doesn't end there. Let me make a shirt of rubber with the same stretchiness as cotton and say it's as comfortable as cotton.

To make this a closer analogy to a bicycle, say you were wearing either rubber or cotton under a suit of armor. There could be a large difference in comfort between the the cotton or rubber layers between you and the armor, but it wouldn't make a whit of difference whether the armor was made of steel or iron.

[spoonrobot]

The frame is the fork. Ride long enough and all the conventional wisdom is true.