kickstart

Auto racers have a saying, "cheap, fast, reliable, pick any two but you can't have the third. Everything is a compromise, CF bicycles are no exception.

spare_wheel

nice aphorism but i'm still waiting for a single citation.
anyone? anyone? bueller?

kickstart

Well, you spent a few hours the internet and know-it-all now, the folks who paid me to work with those materials to their specifications knew nothing. Thanks for clearing up the confusion.

howsteepisit

Show me the facts, and I am 58, not nearly a whelp. But if you can show me any facts other than your opinion I will happily stand corrected. At least I took the time to try to find some relevant research, did you?

prathmann

One test along these lines was conducted for 'Tour' magazine back in '97. A rough english translation of their findings is here:
EFBe Biketest: TOUR-Frametest
The CF frames tested at that time did quite well in this test. Although some questions have been raised about the test procedure it does appear to at least represent a good faith effort to simulate the stresses a frame might experience during a hard, out-of-saddle sprint by a strong rider.

kickstart

Like I stated earlier, I'm not an engineer and haven't done any internet research the subject so I cant provide you the "facts" as you put it. I'm not stating my "opinion", I'm simply sharing what I was taught in the use, maintenance and repair of composites.
I'm not an expert, I did the dirty work for those who were.

Typo fixed, the p is too close to the l for my fat fingers, sorry.

yugyug

A few minutes searching. None of these relate to use of CF-epoxy composites in bicycles. I would be cautious in drawing any conclusions from such research relevant to CF bikes. I’m not a scientist and I’m not making any claims by posting these references other than to indicate that research exists on CF composites failing under certain conditions - none of which may be relevant for CF bikes, though it might. There are, probably, hundreds more similar studies, indicated by the bibliographies of these articles.

Effects on carbon fibre epoxy composites from:

weather/temperature cycles
Li, H., Xian, G., Lin, Q. and Zhang, H. (2012), Freeze–thaw resistance of unidirectional-fiber-reinforced epoxy composites. J. Appl. Polym. Sci., 123:*3781–3788. doi:*10.1002/app.34870

Effect of Thermal Cycling on Hardness and Impact Properties of Polymer Composites Reinforced by Basalt and Carbon Fibers
Reza Eslami-Farsani, Seyyed Mohammad Reza Khalili, Moslem Najafi
Journal of Thermal Stresses
Vol. 36, Iss. 7, 2013

humid environments
J. I. Cauich-Cupul, E. Pérez-Pacheco, A. Valadez-González, P. J. Herrera-Franco
Effect of moisture absorption on the micromechanical behavior of carbon fiber/epoxy matrix composites
Journal of Materials Science, October 2011, Volume 46, Issue 20, pp 6664-6672

B.C. Ray, Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy composites, Journal of Colloid and Interface Science, Volume 298, Issue 1, 1 June 2006, Pages 111-117, ISSN 0021-9797, https://dx.doi.org/10.1016/j.jcis.2005.12.023.
(Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy composites)

creep (slow deformation from mechanical stress over time)
W.K. Goertzen, M.R. Kessler, Creep behavior of carbon fiber/epoxy matrix composites, Materials Science and Engineering: A, Volume 421, Issues 1–2, 15 April 2006, Pages 217-225, ISSN 0921-5093, https://dx.doi.org/10.1016/j.msea.2006.01.063.
(Creep behavior of carbon fiber/epoxy matrix composites)

spare_wheel

The hygroscopic study showed a small effect on strength (~5-15%) but did not perform statistical analysis. However, this study used non-structural single weave laminate with no clearcoat/paint. Laminates used structurally for bike frames typically use multidirection lay ups, a variety of fabrics, and are always clearcoated or painted.

The creep behavior manuscript use two plys of unidirectional weave of unknown modulus. They used a low pressure "painted on" method which is never used for structural carbon fiber. Moreover, their model suggested that 50 years of exposure at 86 F resulted in only a ~18% reduction in modulus. A more significant effect was seen at much higher temperatures but I don't consider this to be realistic. Who stores their bike at 122 F for 50 years?

The final paper looks to be more interesting but it's pay-walled for me so I could not assess the test conditions.

I really don't find much to be concerned about. In fact, I'd be far more concerned about rust or oxidation of metal frames over a 50 year period than any hypothetical CF fatigue.

meanwhile

Did anyone here not know of the delamination/hidden damage risk for CF bikes? Or that they're more likely to suffer sudden rather than slow failure? I hope not.

Otoh, most people buying CF hybrids probably have no idea. The risk is low, but people should be warned before they buy out of fairness and so they can evaluate crash damage intelligently.

spare_wheel

Got a link to go with that statement or are you also relying on anecdote to support your fear mongering.

I've had multiple metal frames fail suddenly but I would never wander around uttering dire warnings about "hidden damage" and "metal fatigue". There will always be failures when frames are crashed or subjected to high stress. The irony is that I actually switched to carbon fiber, in part, because it's more fatigue resistant than metal. In fact, my second carbon frame was a Trek warranty replacement for the two aluminum frames I broke in the span of 3 years. Evidently Trek believed that I won't crack a carbon frame as easily...and they were right.

rebel1916

Piffle, pure piffle.

meanwhile

Ok: so we do have at least one completely ignorant person.

Read

Carbon fiber composite inspection procedures

Pound for pound, carbon fiber is stronger that steel or aluminum. But it behaves differently when it is overloaded in an accident or impact. An overloaded metal part will bend or deform before it breaks, showing evidence of the load (Figure 1). An overloaded carbon fiber part will not bend or deform, so a damaged carbon part (with reduced strength due to the damage) may look normal�even after the same load that bent the metal part. But when the sum of the forces finally exceeds the strength limit of the carbon fiber, the carbon fiber part breaks, it does not bend (Figure 2).

In an accident or impact that does not visibly break the carbon fiber part, the carbon fiber could still have internal or hidden damage. If there is any possibility of hidden damage, please carefully read these instructions and examine the carbon fiber. The following tests are not conclusive. If you are not sure a part is safe, replace it. We offer a very generous crash replacement program. If you crash your carbon bicycle or part, you should visit your dealer to learn more about this program.

Warning�Carbon fiber parts with damage can break suddenly, causing serious injury or death. Carbon fiber can conceal damage from in impact or crash. If you suspect your bicycle has had an impact or crash, immediately stop the bicycle. Replace the part before riding or take the bicycle to your Gary Fisher dealer for service.

It's not that CF is worse than steel or alu - in many ways good CF is better (there's a lot of mediocre CF around, of course) than metal - CF bike frames undoubtedly hold up to professional racing better than lightweight metal ones.

But you do have treat CF differently with regard to accident damage - you inspect it yourself using the "tap" technique and then, if you have any doubts, go to a really competent bike store.

..And if you're buying a used CF bike, then you go over inch looking for loose fibres and doing the tap test (that link to Fisher explains how.)

Then you must be doing something very wrong indeed. Which shouldn't surprise anyone, given that you got angry about a subject you obviously know nothing about and didn't have the wit or patience to check for yourself.

Anyway, bottom line:

- CF generally good - better than metal in some contexts

- But has to be treated with respect and knowledge

..Just like fire and antelope femur clubs, really. No one should be put off buying a CF bike, especially a performance one, they should just know how to treat it. (So I suppose the habitually and determinedly ignorant should be put off buying a CF bike.)

meanwhile

..And we have another "expert" who doesn't know the first thing about his elected area of expertise. Go read the information provided by the nice people at Fisher who actually make CF bikes and have engineering degrees.

spare_wheel

Nice job responding with ad hominems and an irrelevant link. I posted multiple comments (and links to cf repair shops) that covered the need to inspect crashed parts and frames above so you have brought nothing new to this conversation.

You made a blanket statement about delamination and hidden damage and still haven’t supported it.

LOL! According to "meanwhile" metal frames and parts are impervious to being "crashed or subjected to high stress."

meanwhile

I said that delamination was possible after a crash and that it was invisible and needs inspecting for using techniques that metal frames don't require. Which is what Fisher say. If you think I made a statement other than that delamination is a problem and needs a knowledgeable eye to look for it, then quote that part of what I said. If I did say that, I was certainly wrong and will say so. (But I didn't; you just made a childish error in reading.)


Nope: I didn't say that. I said the opposite - that except that the need for more sophisticated inspection CF frames are superior, notably in strength per weight:

me:
It's not that CF is worse than steel or alu - in many ways good CF is better (there's a lot of mediocre CF around, of course) than metal - CF bike frames undoubtedly hold up to professional racing better than lightweight metal ones.

But you do have treat CF differently with regard to accident damage - you inspect it yourself using the "tap" technique and then, if you have any doubts, go to a really competent bike store.

..If you read this as "METAL FRAMES CANNOT BE DESTROYED!!!" then you have a problem and should seek professional help. Again, if you differ, quote the relevant part of what I said.

meanwhile

Oh - there's one other problem with CF bikes: strength in CF is directional so stresses have to be planned for. A CF crit bike will probably resist a head-on impact better than an alu one, but it will more easily damage by a minor impact from above to the top tube or chainstays. This problem gets worse in more expensive bikes because they put very high modulus but brittle CF there (there are four or 5 different categories of CF in regular use, and high end bikes use 3 or 4 in their frames.) Unlikely to happen and nothing that should stop anyone from racing one, but again, more complex than "spare wheel" (whose profile name pre-ad homs him, although he doesn't use the word correctly) and the like think.

Again, CF is an excellent material for performance bikes but knowledge is your friend (although other people's stupidity can be a rich source of amusement.)

spare_wheel

No you did not:

https://www.bikeforums.net/advocacy-s...l#post17036675

rebel1916

Balderdash. Pure balderdash.

meanwhile

But you've agreed with that - delamination is a risk for CF bikes. You've said that elsewhere in the thread you told people how to inspect for it, so obviously you agree!

Yes: if a CF bike suffers a structural failure then it will probably be fast - as Fisher says - rather than slow.

So I made two statements you object to. One is one you made yourself; the other is baked up by Fisher....

Realistically, you're (probably) not insane, so I presume the problem is that you can't read at an adult normal level and interpreted "Did anyone here not know of the delamination/hidden damage risk for CF bikes?" as "CF bikes are LIKELY to delaminate" and "Or that they're more likely to suffer sudden rather than slow failure?" as "CF bikes are more likely to fail than metal bikes". (In fact it makes no statement of the relative likelihood of failure at all - the only comparison of likelihoods is between the modes possible for a CF bike.)

So, very simply, you got angry and made a big fuss because you can't read quite simple sentences. Now, we can't all be the sharpest knife in the draw, but when we're not, then we should use our words to ask people questions until we are sure that we understand, yes? Instead of ranting...

spare_wheel

More ad hominems and more patronizing comments.

And let me quote my comment immediately above:
It is always amusing when someone attempts to "educate" me by repeating the gist of comments I made earlier in the same thread.



WTF? Does the fact that I happen to ride crabon bikes for every day utility offend you or something.

Here is my first repair ('08 Calfee):



The small ding is recent and at some point I will sand it down and re-apply clearcoat. I sure hope my frame does not "delaminate" "meanwhile".

spare_wheel

Dudette/Dude, this is not 4Chan.

meanwhile

Good: if I was you I'd need something to laugh at.

I'm sorry: I can't understand the level of poor reading skills required to reach your conclusion. I commented on your lack of understanding of the engineering of CF frames; what does this have to do with sort of bike you ride or my feelings about that? You can ride whatever sort of bike you like, my interest is (out of kindness) correcting your reading errors.

..And nowhere did I say that CF frames can't be repaired. Again, learn to read, young man, learn to read!

(Otoh, I really wouldn't want to ride a bike that you think you've repaired...)

Once again:

- CF bikes have many advantages

- They do have the disadvantage of having hidden delamination damage, which is hard to detect, and can lead to sudden failure

- If anyone reads this as "CF bikes break more easily!"... then they should go back to their high school and demand their parents taxes back. Unless the problem is genetic, in which case they should apologize to the teachers instead

...That a bike is harder to inspect is NOT the same as it being weaker or more failure prone! However much this may confuse some simpler minds.

spare_wheel

the repair was performed by calfee.

calling this "hidden" is pure FUD because the chances of this happening without a crash or blow are infinitesimally small.

moreover, companies like calfee have a 20+ year track record of repairing carbon frames. it's not @#$%ing rocket science.

https://calfeedesign.com/repair/

Pibber

I know people with steel frame bikes that have broken, too. The thing that makes it worse for C-dale is that the stupid name rhymes. I own four from 84 to 99. No problems. And, yeah, gt's have broken too.

BigSkyFatGuy

I'm 260 pounds. I ride a carbon fiber bike every day.
If it doesn't break with me on it, you little fellas have nothing to worry about.