I will say in the automotive world, you are much more correct as tires run at much higher slip angles. In the biking world, its primarily the tradeoff of rolling resistance to grip, not alot of technology in bike tires comparively.

In about 15 minutes I could, it's all ideal gas you know. Introducing slip angle means either you're trying to throw up smokescreens or you just wandering all over the place. In either case, that's where I stop reading.

The original post raised the question of effects of frame material on ride quality, but showed no thought on how to separate design effects from material ones. There is plenty of factual information on material properties of common bicycle materials. The problem is interpreting them in light of the infinite possible design space.

Unfortunately, there just isn't a lot of data out there. Or at least, there isn't some sort of established methodology to which a manufacturer or 3rd party adheres. I.e. it seems that the scientific data just isn't there.


1) Precise, repeatable, credible, consistent methods -- particularly ones that work in the field, rather than in a testing environment -- are not particularly easy or cheap.
2) You'd have to test specific framesets, not frame materials. A given frame material can be stiff or compliant -- especially CF, which has a huge possible range of characteristics, which will be determined in actual use by the designer's goals (and skill with the material).
3) You'd have to test a pretty large sample of frames. Again, not easy or cheap.

So in the absence of published scientific tests, unfortunately it seems like your only options are to a) trust the manufacturer's descriptions and/or b) trust the expertise of anyone who has time to review the specific bike you're interested in and/or c) hope your subjective judgments aren't overwhelmed by your expectations.

And then that would only tell you how that frame performed, not a measure of "goodness." That's because there is no single standard of performance for frames. Some designers are trying for a very "soft" or "compliant" frame others want "stiffness" above all else. For the vast majority, the goal is some balance in the middle. To that end, they will specify frame geometry, tube geometry, thickness, material, gussetting, and the list goes on and on. All these factors will influence the performance of the final product. As consumers, the best we can do is find the frame which most closely matches out personal preferences and not worry about how the designer accomplished that result.

thats fine if you dont care, there are plenty of other threads to discuss the subjective nature.

How does the "designer" accomplish his final result? he knows the influence of the design parameters, precisely what we are trying to discuss here. The designer is truly an engineer because he understands the objective factors to create the final 'subjective' feel.

Or - and I know that this is crazy - we could get people to actually listen to materials scientists/engineers (and no, not just any old engineer... too many engineers out there think that their fancy degree means that their intuitions are correct) when they describe the actual effects that material has on structural design. There's no need to do some complicated and probably utterly confounded test when:

a) the properties of the materials in question are known. That is to say, if an appropriately qualified engineer were to design a frame with X material in Y dimensions and Z geometry, the exact flex, stiffness, etc of any given frame can be determined strictly by application of theory. There are little details that are difficult to account for that contribute to feel, but those are not much easier to measure than they are to design. C'mon. Do you think that the engineers who design those fancy pants carbon bike are able to make them stiffer each year through guesswork? No, it's the specific application of a material with known properties. The same thing can be done with steel, aluminum and titanium, in principle, though frame design need not be done in such detail.

b) No one will care or pay any attention to the results. People's prejudices and preconceived notions are far more powerful than mere data. See a), above: the information needed to demonstrate that frame materials only change the parameters of design rather than having some essentialist effect on the ride of a given frame is already out there. The problem is that no one pays it any attention, they just cling to their beliefs. Collecting yet data on this would only be a colossal waste of time. There is no shortage of fact out there. There is also no shortage of credulous people.

Actually, no. Let's go to the text:
You say this is easy, but you have not presented any test which would separate out the influence of design from material. A simple example shows why this is not only difficult but unrealistic. Compare and contrast the ride characteristics of a Vitus 929 and a Cannondale CAAD 3 with special attention to the role of frame material.

:rolleyes: ah the joys of BF...

so how do you suppose they design automobiles? or are bicycles that much more complex? Yes that is a rhetorical question. Ah! too many variables

So you're claiming there's an inherent difference in the ride quality between steel, aluminum, and fiberglass bodied automobiles?

Ride quality depends on flex at least as much as material damping. Steel for example, doesn't damp very well but many people laud the ride quality because the typical steel frame, made with small diameter tubes, flexes in response to road inputs. Aluminum on the other hand, is a more flexible material than steel but because of fatigue related concerns, the typical Al frame is designed to reduce flexing in order to preserve frame life. Bottom line is that trying to measure frame characteristics would be relatively meaningless unless the testers are prepared to measure many many variables to quantify the various differences between all the frames given both design and material considerations. Good luck with that.

:roflmao2: no... i was just making fun of you and your negative comments. (just being honest)

and you completely missed the point of my post...;)

So to stay away from the ad hominem, why should there be an inherent difference in ride characteristics of a bicycle based on material of construction?

well actually the material that vehicles are made of does play a role in ride quality. The chassis stiffness both beam and torsional rigidity plays a role which is a function of geometry and material properties. However, vehicles have suspension and the % influence on ride quality from chassis material is minor.

On a bicycle, there is no suspension, thus the chassis(frame) stiffness will be a much larger portion of the overall ride quality.

did you really need me to explain that for you?

O.K. If you want to play, you're really going to have to pay attention. When I wrote, "why should there be an inherent difference in ride characteristics of a bicycle based on material of construction?" That's what I meant; I used the word inherent for a reason. So do you believe a car with a steel body would have ride characteristics resulting purely from the body being made of steel which could not be replicated with a body made of another material?

I do like the way you shift back and forth between automobiles and bicycles in your examples depending on which you think you can better twist to suit your argument.

I dont have an argument.... you have an argument. I dont understand what you are trying to prove by nit picking wording on an internet forum. Yes materials have different properties? is that what you want to hear?

I really could care less what you think, my post was intended to inspire a slightly higer level of thinking on BF compared to the typical "carbon rides better" comments. If you think we should go back to that, by all means, feel free.

If you could refrain from posting again in this thread, it would be greatly appreciated.

No, he isn't.

F1 tyre guys - back when they had multiple brands - would engineer their tyres so the rubber left on the road was sticky to their brand but slippery to the other brand.

You can overcome anything except being on the wrong tyre.

DG

Except the subject was not road-tire interaction but tire deformation, and the application was bicycles not cars. For bicycles, this is purely a function of the inflation pressure not the construction of the casing (or the gas used to fill the tire, within reason). So to introduce tread compounds into the discussion is either a joke or a total misreading of the governing physics.

Alright mister king of the world, it is your internet.

But it might be in your own interest to stop and think about what you're writing. You began this thread by proposing an easy, simple experiment to demonstrate how material of construction alone controls ride characteristics. I, and others, have repeatedly tried to point out that this is a fools errand since ride quality depends on design and construction and these two cannot be separated. Even if identical frames were made of different materials, this would not prove the point you are searching for since the design could be optimized for only one material, at best.

So let me end with the following question - since I seem to be too simple to follow your experimental plan, explain how the data you gather from measuring accelerations on frames leads to correlation of comfort level to material of construction?

Hi,

Would you do a standard DOE or a Taguchi DOE? You need to determine the relative sensitivities of the output, vibration, against you variables at different levels. It would be interesting to see if frame geometry is a greater influence on ride comfort than material.

Also for a given geometry, how much influence does bottom bracket and chainstay stiffness have on comfort? Are seat stays the primary influence on comfort as Cervélo would have you believe with their R3 design?

Wounds like a challenging analysis even with a relatively simple system.

no doubt a challenging analysis to do properly

but even if it is just a simple analyisis it would provide some data for better (more interesting) discussion.

Cripes. People keep saying this. It is wrong. There is no need to make an aluminum frame stiff to preserve frame life.

... and still it would mean nothing because of people's self-reporting bias, selection bias, need to please the test administrator, variations due to their health, etc.

You keep thinking that if you control for enough data and variables that the people part will naturally fall into place. That's a fallacy.

Our brains only process an approximation of actual events, our memories are faulty and have predictably unpredictable oddities, and what people say is never what they mean. If you require any information that they filter then it's unreliable. People just aren't rational, at the core. That's why marketing is more about emotional appeal, presentation and manipulation than objective information clarity.

Now, if I misunderstood you and you just want to measure frequencies and pop them into a spreadsheet, sure, go for it. But that still won't tell you anything about people.

A) Testing frame materials alone would be impractical to the point of impossible and/or meaningless.
B) You can characterize a huge number of ride characteristics with this type of analysis if you want.
C) It wouldn't be all that expensive (<$10k), especially for a manufacturer.
D) Cars are much, much more difficult to characterize and it's done every day.
E) Car chassis construction plays a huge part in ride characteristics and NVH concerns even with a suspension. Modal analysis of a car chassis is a big part of the design and development of any car.
F) Tires are a huge component. The compound is less important than the construction of the carcass, but they're both players.
G) Rider impressions aren't perfect, but they're a good starting point and when correlated with numerical data can be surprisingly accurate in a qualitative sense.
H) Any manufacturer that isn't doing this isn't serious about building a good bike. Having said that, I don't think it's common practice.

It may be a fallacy, it may not. You can record a person's opinion on ride qualities against the vibration frequencies. If you have a large enough sample size you can statistically determine if there is a correlation between the opinions and frequencies or if there is not.

Your hypothesis is that there is not a correlation. The opposite of your hypothesis may be true.

More like an impossible analysis to do properly.

Your suggestion for an analysis of comfort as a function of material assumes that there is such a function that is based on the inherent material properties. But the evidence is that such an assumption is wrong. The example given earlier of the Vitus 929 vs. Cannondale CAAD frames is instructive in this regard.

The Vitus frames were almost universally reviewed as being very flexible and giving a cushy, highly comfortable ride. Racers liked them for the light weight but some claimed that the flex made them inefficient. Nevertheless, they were raced successfully, so the efficiency can't have been all that bad. [And, BTW, the Vitus frames disprove the idea that Al frames must be stiff to be durable enough for bicycle use; some did have failures but those were almost all at the bonded joints.]

The Cannondale (and Klein) frames got exactly opposite reviews. Praised for being extremely stiff with no wasted energy going into flexing the frame. But some claimed that the lack of compliance made them too harsh riding and uncomfortable. Nevertheless, many were successfully used on long endurance event rides, so apparently the comfort can't have been that bad for everyone.

So two frames, made of the same material, can have diametrically opposite evaluations on the qualities of comfort and stiffness. Good luck on finding that 'comfort function' that's determined by choice of frame material.

...and you know this how?

Almost every Al frame in the marketplace uses thick large diameter tubes to reduce flex in the interest of reducing frame fatigue. Are you suggesting that almost every Al frame builder/tubing manufacturer/OE builder doesn't know what they are doing?

Dr. Cox: I heard "I know I'm being annoying," and then...white noise.

exactly

Quantifying ride quality for whom? For the measuring device (the engineer) or for the discriminating rider who may be a pro rider on a race. In the Tour, a rider may have 3 different bikes. On the Paris Roubaix, the bikes may change out forks for different wheels because of the cobblestones.

In the end, its not about a debate, its about the riders and their race situation. The two engineers who started a bike company in Toronto started a new team and called it Cervelo Test Team. Guess what they were testing and who do you think they were asking to test them?

I'd like to see a list of relevant parameters. It will be a very, very long list.