Gravel bikes with horizontal (trad geo) top tubes?

[ChristianWong]

Originally Posted by colker

What vertical compliance are you talking about? Some frames by measure of tube diameters, longer chainstays or even a taller handlebar make for a more comfortable bike when riding over rough roads. Low profile rim wheels. Less air on fatter tires. These make sense. Now you can call "cognitive dissonant" (an elegant way to call others dumb) all day but that won´t be vertically compliant too.

If low profile rim compliance makes sense, why doesn't seatpost flex?

I ride big bikes with long seatposts and I'm not a lightweight. If I look down (usually on my trainer), I can see my seatpost flexing. Switching from an aluminum Thomson to a titanium Firefly post, I can absolutely feel the difference. There's a reason titanium seatposts are popular on mountain bikes, where there is a significant amount of exposed seatpost.

[Clancy]

5 pages on level top tubes?

Must be winter

[Mark McM]

Originally Posted by colker

What vertical compliance are you talking about? Some frames by measure of tube diameters, longer chainstays or even a taller handlebar make for a more comfortable bike when riding over rough roads. Low profile rim wheels. Less air on fatter tires. These make sense. Now you can call "cognitive dissonant" (an elegant way to call others dumb) all day but that won´t be vertically compliant too.

Looking for extra compliance in low profile rim wheels makes the least sense of anything. No spoked bicycle wheel has been shown to have any significant compliance (in the Cervelo test referenced previously, wheels had the smallest compliance of any of the components [1]). When measured in the lab, low profile rim wheels actually tend to have less compliance than deep profile wheels (this is because low profile wheels tend to have more spokes [2]). In blinded tests, riders have been unable to distinguish between wheels with low and high profile rims [3]. Believing that low profile wheels make a difference in compliance but seatposts don't is definitely a case of cognitive dissonance.







[1] https://www.cervelo.com/en/ride-quality




[2] https://blog.silca.cc/road-to-roubai...lete-story-1-0

Like the athletes, we believed that the real hurdle to bringing carbon wheels to Roubaix was going to be comfort. The entire world believed that there would be no way to achieve the ‘comfort’ or ‘compliance’ of box section wheels in deeper wheels. After-all, we all KNEW that deeper wheels were stiffer, and therefore harsher, it had been written a thousand times and was therefore true. So in late 2007 we set out to understand the baseline standards for both durability and comfort in these ‘classics’ wheels.

An Instron machine, is generally the cornerstone of any good mechanical testing lab. Instron is the company most widely known for making this type of machine which looks like a large H sitting on a steel table. The machine works by driving a crossbar up or down at a very controlled rate, in the center of the cross-bar is a load cell and a gripper, or a pusher (anvil) which either stretch or crush the object being tested. An Instron can be used to test the strength and stiffness of most anything provided you have clever engineers to build the fixturing.

The initial testing was conducted with about a dozen wheels including prototype Roubaix wheels, vintage Mavic Roubaix aluminum box section wheels, and the 2007 race favorite 32 spoke Ambrosio Crono box section rimmed wheels. After the first full day of testing, crafting new anvil geometries, re-thinking the fixtures, re-thinking everything we could be doing wrong, we realized that we weren’t doing anything wrong at at all: The box section wheels were in fact, radially stiffer than most of the deeper carbon wheels!

[3] https://www.slowtwitch.com/Tech/Thou...tion_4571.html

One of the major discoveries was that after controlling for seat post (round post shimmed into aero frame so as to not give it away) not a single rider found the aero road bike to be less comfortable, less compliant, etc, than the identically setup 'endurance' or 'roubaix' bike (clearly this leaves room for the aero seat post to be why people feel aero bikes are less compliant..seatposts generally have more effect on bike compliance in the lab than frames do, but that's another story). We ran blind wheel tests a couple of times a year at Zipp to benchmark competitive wheels and our own prototypes, and we also found that blinded riders were generally unable to tell the difference between stiffness and inertia, had no reliable feedback on weight, lateral stiffness, or comfort in general, and in the end were generally only able to pick out the aero wheels because they were riding laps around a closed park environment using power, so the more observant ones would notice speed differences. In the end, we sort of determined that when riders didn't know what they 'should' feel, they really struggled to find differences in stiffness, compliance and weight between frames or wheels.

[Smitty2k1]

Guess that's a good reason to live the #supplelife

[colker]

Originally Posted by Mark McM

Looking for extra compliance in low profile rim wheels makes the least sense of anything. No spoked bicycle wheel has been shown to have any significant compliance (in the Cervelo test referenced previously, wheels had the smallest compliance of any of the components [1]). When measured in the lab, low profile rim wheels actually tend to have less compliance than deep profile wheels (this is because low profile wheels tend to have more spokes [2]). In blinded tests, riders have been unable to distinguish between wheels with low and high profile rims [3]. Believing that low profile wheels make a difference in compliance but seatposts don't is definitely a case of cognitive dissonance.







[1] https://www.cervelo.com/en/ride-quality




[2] https://blog.silca.cc/road-to-roubai...lete-story-1-0





[3] https://www.slowtwitch.com/Tech/Thou...tion_4571.html

I see: cognitive dissonance is not accepting anything you or cervelo say as wisdom.
Sorry but a lot of people won´t. I have a titanium seatpost and it does not move. Btw; it´s campagnolo. Sometime later campa changed it to carbon. It does not move as well. It´s a freaking single tube almost vertical in any bike.
Wheels otoh are complex structures and every single element from rim, tire to any of the 32 spokes are acting as a shock dispersing unit. Wheels are the most complex structure on a bicycle. You can rinse and repeat the words cognitive dissonant but my experience says a seatpost holds a saddle in place and does nothing else. It also says there are harsh wheels and comfortable wheels.

[Mark McM]

Originally Posted by colker

I see: cognitive dissonance is not accepting anything you or cervelo say as wisdom.
Sorry but a lot of people won´t. I have a titanium seatpost and it does not move. Btw; it´s campagnolo. Sometime later campa changed it to carbon. It does not move as well. It´s a freaking single tube almost vertical in any bike.
Wheels otoh are complex structures and every single element from rim, tire to any of the 32 spokes are acting as a shock dispersing unit. Wheels are the most complex structure on a bicycle. You can rinse and repeat the words cognitive dissonant but my experience says a seatpost holds a saddle in place and does nothing else. It also says there are harsh wheels and comfortable wheels.

Perhaps your sample size is too small. As mentioned earlier, seat post flex varies as the cube of free length. Short seat posts flex very little, and long seat posts can flex quite a lot. I've got two bikes (with horizontal top tubes) with very little exposed seat post, and seat post flex can't be seen by the naked eye. But I've also got two bikes (MTBs with steeply sloped top tubes) with very long exposed seat posts, and seat post flex is quite visible by eye.

Your explanation of wheel compliance is putting the cart before the horse. Before you try to explain wheel compliance, you first have to confirm it exists. Those who have tried to confirm wheel compliance have found that there is almost none.

[kingpin75s]

Originally Posted by Mark McM

Perhaps your sample size is too small. As mentioned earlier, seat post flex varies as the cube of free length. Short seat posts flex very little, and long seat posts can flex quite a lot. I've got two bikes (with horizontal top tubes) with very little exposed seat post, and seat post flex can't be seen by the naked eye. But I've also got two bikes (MTBs with steeply sloped top tubes) with very long exposed seat posts, and seat post flex is quite visible by eye.

Your explanation of wheel compliance is putting the cart before the horse. Before you try to explain wheel compliance, you first have to confirm it exists. Those who have tried to confirm wheel compliance have found that there is almost none.

As someone who runs Ti seat posts from Eriksen, Potts, Black Sheep and Dean along with a number of Thomson posts, I would agree with your statement. I run long posts (mountain) and short posts (road) and the above rings true. I would also add that wall thickness (and diameter) plays a key part in flex. As such, not everyones experience will be the same. As an example, my Dean posts from the 90s have more flex than my current posts from Eriksen, Potts and Black Sheep. I notice it most when riding my rigid Dean where it is very obvious.

[nmrt]

I have a Ti bike that I run with Enve 3.4 carbon wheels (rim depth: Front 38 mm, rear 42 mm; 20/24) The bike feels so stiff.
Then I swap the wheels to another carbon rim (rim depth 21 mm; 20/24) and the bike feels so much more complaint. Both wheels have the same tire.

I am only a sample size of one. I am the first to admit bias or placebo. But in this case, the difference between the deeper Enve 3.4 and the shallower (18 mm depth) carbon wheel is night and day. I just cannot begin to tell you how different they ride and how much more comfortable the shallower rim feels.

Originally Posted by Mark McM

Perhaps your sample size is too small. As mentioned earlier, seat post flex varies as the cube of free length. Short seat posts flex very little, and long seat posts can flex quite a lot. I've got two bikes (with horizontal top tubes) with very little exposed seat post, and seat post flex can't be seen by the naked eye. But I've also got two bikes (MTBs with steeply sloped top tubes) with very long exposed seat posts, and seat post flex is quite visible by eye.

Your explanation of wheel compliance is putting the cart before the horse. Before you try to explain wheel compliance, you first have to confirm it exists. Those who have tried to confirm wheel compliance have found that there is almost none.

[Mark McM]

Originally Posted by nmrt

I have a Ti bike that I run with Enve 3.4 carbon wheels (rim depth: Front 38 mm, rear 42 mm; 20/24) The bike feels so stiff.
Then I swap the wheels to another carbon rim (rim depth 21 mm; 20/24) and the bike feels so much more complaint. Both wheels have the same tire.

What mode of stiffness/compliance are you sensing? Wheels can behave differently to lateral, radial, and torsional loads.

Wheels can have significant flex laterally. Wheel lateral stiffness is most commonly sensed when pedaling hard out of the saddle (particular if the bike is rocked side to side), or when doing rapid steering maneuvers. On the other hand, all wheels have very little radial (vertical) flex. So there should be no difference in compliance to vertical forces (such as road bumps). Wheels with crossed spokes also very little torsional flex (although lateral flex can sometimes be confused for torsional "wind-up").

[DreaminJohn]

Originally Posted by polar8

Great build. Who makes that frame?

If that had an internal hub I'd marry it.

Just sayin'.

[nmrt]

One difference that I feel between the two wheels is that with the Enve when I go over road imperfections, it is jarring. But with the other wheelset, the result is not even close to jarring. the bike just seems to float over it. It feels comfortable, relatively.

Originally Posted by nmrt

I have a Ti bike that I run with Enve 3.4 carbon wheels (rim depth: Front 38 mm, rear 42 mm; 20/24) The bike feels so stiff.
Then I swap the wheels to another carbon rim (rim depth 21 mm; 20/24) and the bike feels so much more complaint. Both wheels have the same tire.

I am only a sample size of one. I am the first to admit bias or placebo. But in this case, the difference between the deeper Enve 3.4 and the shallower (18 mm depth) carbon wheel is night and day. I just cannot begin to tell you how different they ride and how much more comfortable the shallower rim feels.

[JAGI410]

Surly Cross Check!

[Mark McM]

Originally Posted by ChristianWong

I ride big bikes with long seatposts and I'm not a lightweight. If I look down (usually on my trainer), I can see my seatpost flexing. Switching from an aluminum Thomson to a titanium Firefly post, I can absolutely feel the difference. There's a reason titanium seatposts are popular on mountain bikes, where there is a significant amount of exposed seatpost.

This is why seat post flex should be undeniable - it can be large enough for anyone to see with the naked eye, as in the above example. This is in contrast to frame and wheel compliance, which is so small it can't be seen by the unaided eye.

[Mark McM]

Originally Posted by nmrt

One difference that I feel between the two wheels is that with the Enve when I go over road imperfections, it is jarring. But with the other wheelset, the result is not even close to jarring. the bike just seems to float over it. It feels comfortable, relatively.

You may be sensing a difference between the wheels, but with exception of the tires, it is unlikely that it is any difference in the wheels. Here's a personal anecdote of this: Many people assume that wheels with deep section rims will ride more harshly. But after I got my first set of deep section wheels, my first riding perception of them is that they had a smoother ride than my shallow section wheels. Intellectually, I knew that there really shouldn't be a difference at all. As I wondered about this while riding the deep section wheels, I realized that my new deep wheels were also quieter than my shallow wheels. My mind had been associating quietness with smoothness, so the smoothness I was experiencing was merely what my subconsciously had been expecting.

Back to the wheel compliance: The vertical stiffness of a variety of wheels has been measured several times, and its been found that wheels typically have stiffnesses in the range of 10,000 - 20,000 lb/in. One of these tests by Josh Poertner at Zipp wheels was already referenced above, and here's another test that shows vertical wheel stiffness. This means that even large vertical forces result in little wheel compression (compliance). Even at the low end of wheel stiffness, a "hit" that generated a force of 100 lb. on the rider would compress the wheel only about 0.010" - about the same as the the thickness of 2 sheets of paper. This is far less than the compression of handlebar tape, for example, let alone the much larger compression of the tires. The amount of wheel compression is so small, that it is unlikely that a rider could sense this amount of compliance at all, let alone the even smaller difference there might be between two different wheels.

Of course, I'm not the only one who's reached this conclusion. Josh Poertner's experience at Zipp wheels led him the same conclusion, just as it did the engineers and wheel designers at Nox Composites wheels:

Let’s talk a bit about vertical compliance. We often get questions like “are carbon wheels too harsh?” or “I heard carbon wheels make the bike really uncomfortable, is that true?" The short answer is no, you will not be able to tell any difference in vertical compliance between a carbon wheel and an aluminum wheel. In short, changes in vertical compliance between two wheel setups can be contributed to other factors like tire volume, tire casing, tire pressure, frame flex, handlebar flex etc., not the wheel setups. No spoked bicycle wheel, even super-light alloy wheels with thin gauge spokes, have enough vertical compliance for you to feel a difference.

Needless to say, the late Jobst Brandt had already written about this in his seminal book "The bicycle wheel", written over 40 years ago:

Stiffness, in its various forms, is a subject often discussed by bicyclists with a regard to components as well as frames. Stiff wheels are often mentioned with approval. However, it should be noted that a bicycle wheel is so rigid that its elasticity is not discernible because the tires, handlebar, stem, frame and saddle have a much greater combined elasticity. Therefore, the differences between well constructed wheels are imperceptible to a rider. The “liveliness” attributed to “stiff” wheels is an acoustic phenomenon caused largely by lightweight tires at high pressure and tight spokes with a high resonant frequency. This mechanical resonance can be heard, and possibly felt in the handlebars, but it is not related to the wheel stiffness.

There are some people who are convinced that they can feel the difference in vertical compliance between wheels. But its likely those people have never tested this ability in a blinded test (a test where the wheels were hidden from the rider). Those who have tested wheels in blinded tests have found that they couldn't feel differences in wheel compliance (see the reference to the Zipp blind wheel test previously referenced).


(Side note: It's amazing to find how many obvious differences disappear when test subjects are blinded. There is plenty of information available on blind tests of other things, such as wines and violins, but there are a few on bicycle products as well. Here's an interesting one: You'd think that riders would be so sensitive to different saddles that they should easily be able to tell them apart by sitting on them, but in this blind test of Fizik saddles only half the riders could actually distinguish between two different saddles.)

[nmrt]

Mark,
Thanks for the response. I appreciate it. As a scientist, you do not have to convince me of what you are saying. I really wish I could do a blind test here. But I cannot. And I know the tests say that I should not feel a difference between the two wheelsets. Maybe it is, as you said, a case of confirmation bias. But it is not a case of tires, as you propose. Both the wheels have the exact same tires at the same pressure.

I am convinced that I am feeling something. Because there are many cases where I think I feel something (stiffness in the BB because of O/S tubes etc etc) but I tell myself that I am imagining it. But here in this case, I am feeling something for sure. While I do not doubt studies that reveal minimal/imperceptible difference in stiffness between wheels, I want to think that there is something else that I human mind can perceive in the totality of the riding experience and notices subtle differences that studies have not yet identified and hence have not quantified.

Or maybe this is a classic case of confirmation bias. I cannot discount this. Just as I cannot discount that I notice a night and day difference between these two wheels.

Originally Posted by Mark McM

You may be sensing a difference between the wheels, but with exception of the tires, it is unlikely that it is any difference in the wheels. Here's a personal anecdote of this: Many people assume that wheels with deep section rims will ride more harshly. But after I got my first set of deep section wheels, my first riding perception of them is that they had a smoother ride than my shallow section wheels. Intellectually, I knew that there really shouldn't be a difference at all. As I wondered about this while riding the deep section wheels, I realized that my new deep wheels were also quieter than my shallow wheels. My mind had been associating quietness with smoothness, so the smoothness I was experiencing was merely what my subconsciously had been expecting.

Back to the wheel compliance: The vertical stiffness of a variety of wheels has been measured several times, and its been found that wheels typically have stiffnesses in the range of 10,000 - 20,000 lb/in. One of these tests by Josh Poertner at Zipp wheels was already referenced above, and here's another test that shows vertical wheel stiffness. This means that even large vertical forces result in little wheel compression (compliance). Even at the low end of wheel stiffness, a "hit" that generated a force of 100 lb. on the rider would compress the wheel only about 0.010" - about the same as the the thickness of 2 sheets of paper. This is far less than the compression of handlebar tape, for example, let alone the much larger compression of the tires. The amount of wheel compression is so small, that it is unlikely that a rider could sense this amount of compliance at all, let alone the even smaller difference there might be between two different wheels.

Of course, I'm not the only one who's reached this conclusion. Josh Poertner's experience at Zipp wheels led him the same conclusion, just as it did the engineers and wheel designers at Nox Composites wheels:




Needless to say, the late Jobst Brandt had already written about this in his seminal book "The bicycle wheel", written over 40 years ago:



There are some people who are convinced that they can feel the difference in vertical compliance between wheels. But its likely those people have never tested this ability in a blinded test (a test where the wheels were hidden from the rider). Those who have tested wheels in blinded tests have found that they couldn't feel differences in wheel compliance (see the reference to the Zipp blind wheel test previously referenced).


(Side note: It's amazing to find how many obvious differences disappear when test subjects are blinded. There is plenty of information available on blind tests of other things, such as wines and violins, but there are a few on bicycle products as well. Here's an interesting one: You'd think that riders would be so sensitive to different saddles that they should easily be able to tell them apart by sitting on them, but in this blind test of Fizik saddles only half the riders could actually distinguish between two different saddles.)