We are DECADES into carbon fiber use in the bicycle industry and the ignorance and hysteria continues.

It is utterly amazing.

Rec riders need to know what they're riding and consider the implications. Debate about better/worse, safe/unsafe, stronger/weaker misses the point which should be suitability for the purpose.

Just as one wouldn't use a sports car for hauling plywood, or running double track in the woods, those who choose to ride ultralight "racing" bicycles need to understand that they weren't designed and built for heavy loads and a lifetime of rough service. That doesn't mean they're weak or dangerous, just that they're not utility bikes.

Unfortunately the marketing pendulum has swung to the lighter is better side again (not the first time) and that's driving the process for now. Hopefully the dust will settle and people will accept that continued shaving of weight undermines the safety margin, while a few wheel placed grams will greatly improve it with no loss in performance.

I agree with this. I'd buy a new carbon bike...no problem. I have often thought of buying a Trek Domane and if I ever get the scratch together, I just might. I would have a hard time buying a used carbon bike off fleabay though.

I didn't take that article as saying carbon was exploding all over the place...just that it doesn't bend like metals so when it does go, it can shatter.
Is that not true?

It's to do with 'how' it fails when it does.

Reread it. The sports medicine MD specifically says that the carbon explodes. I guess he didn't know he was spelling it wrong. :)

Here is the excerpt which I probably shouldn't reprint, but it is for academic purposes and I give full credit to the NY Times:

“Anyone in a team who’s being honest with you will tell you how frequently their bikes are breaking; everybody knows,” said Mark Greve, a physician and assistant professor of sports medicine at Brown University who studied injuries to 3,500 competitive cyclists. “Few people in the public appreciate how many bikes a pro team will go through in a season, because they break for one reason or another. The bikes, they completely explode.”

...I want to file a protest. :notamused:

...I'm OK if you're the winner, so long as you pass the blood screening. I just want to podium. :)

Is the doc wrong?

Certainly carbon fails much differently than steel, aluminium, or titanium in bikes. It's been my personal experience that when carbon fails, it usually looks like it "explodes" in the sense that the failure happens rather rapidly. Usually, the end result looks as though the carbon exploded too.

Well, there are vested interests playing on nostalgic impulses and the need to justify a purchase as "the best" rather than simply as "appropriate".

The difference simply lies within the stress strain curve of carbon fiber versus, steel, aluminum, or stainless steel.

Carbon fiber composites have no yield, they fail instantaneously when they reach their critical load point. The other materials yield, means they survive integrity even although they change dimensions beyond their elastic limit.

In short, carbon fiber gives no warning before it fractures. As some say it just asplodes.:p

As to the original posters question, the life of CF is indefinite, as chemical and photo degradation only affects the surface, leaving the structure in tact. There is no age risk, other than it cannot be recycled leaving an environmental dilemma to some extent.

Another way of looking at this is if you hit a steel frame with a hammer, the material will yield beyond its elastic limit in a spot leaving a dent. The frame will still be intact with good integrity. If you hit carbon fiber with a hammer it will partly fracture and if the fracture is not clearly visible it could present a nice surprise to the unsuspecting rider at some point, by fracturing completely.

http://i300.photobucket.com/albums/n...psb4f549ba.jpg

Ha. Yes...a doctor and he can't even spell asplode properly. :lol:
It's the dramatic word that's always gone with carbon failure. I suppose the aftermath can look like it asploded though. Bent metal doesn't look nearly as dramatic as a shattered bike laying in bits.

I don't have an issue with carbon per se. I'll have a brand new r3 in a few weeks....I just don't expect to be on it in 20 years like I probably will be on my steel merckx corsa extra.

It starts on a variation of the same opening line: "I was just riding around when................"

I've got an article with health and nutrition advice from an engineer that works with composites - wanna read it?

Your reliance on the stress-strain curve of the type shown is problematic. A bicycle will almost never be subject to stress at such a speed at that kind of test is conducted at. I have a problem considering the possibility of yielding in that type of test as a warning of impending breakage. Both can occur sequentially in response to the same excessive stress in so short a time as to be indistinguishable from each other (by humans). So the yielding would not be of any value as a warning. Also your graph shows that CF composite is unchanged up to as high or higher stress than steel, which actually fails in a yield sense at much lower stress. The fact that steel has a lower modulus after the yield point makes it look "stronger", but it isn't. Going to higher elongation before breaking isn't of any warning value in the case of a violent impact.

Your graph is of stress applied relatively slowly, but still over no more than a few minutes. Many failures occur in response to very rapidly applied stress, properly called impact which isn't represented here at all.

Very long term stresses causing creep that may eventually lead to failure are also common, but that isn't represented by your graph either. You are using a short (but not very short) time application of stress in your argument as if it is a realistic mode of failure. That really isn't a likely scenario. The stresses that will cause failure of a bike frame are applied either very fast (impact) or very slow (creep inducing). Nothing can warn someone about an impending impact whether to steel or CF. It is like an earthquake in that regard. But plastic materials like CF composites subjected to very long term applications of stress do exhibit warning signs before failure such as crazing and micro-cracking.

Yeah, it takes an engineer to know that a bike snapped in half. :rolleyes:

Come on man, is the doctor wrong or not?

I'm confused?

A stress strain tester applies load gradually, not fast.

If you hit a steel pipe with a hammer, which is impact, is it going to fracture of dent? If you hit a steel panel on your car in an accident does it fracture, or does it deform? If you hit a carbon fiber panel, will it leave a dent or fracture?

Steel does fail by fatigue, however it is a long process commencing with a tiny crack, which slowly grows until tensile stress causes the final fracture. These can be hidden.

There is no creep in carbon or alloy steels, neither in Aluminum, neither in Carbon Fiber.

With steel, its alloys and carbon fiber, the speed at which you apply tensile force in a tester will always produce more or less the same stress/strain result with no significant difference, fast or slow. Polyethylene will however give different results by a large margin.

...you're blaming this on Grant Petersen ? :wtf: I don't even agree with Grant Petersen most of the time. Wait, is this ironic ? #whoknowsanymore

...if you look carefully at the photo in the OP, you'll see a KG86 Look frame, that was very early on in this use.

I think maybe it was a LeMond ride, or something way back when. I hope you're not gonna follow up with some
sort of comment to the effect that it ought to be fine because it's lasted this long.

The numbers of frame failures in CF tubed glued into some sort of alloy lugs were one of the things that got the
whole phenomenon of "carbon bad" rolling in the first place.

To the OP: you mention that you will have the frame "inspected" to be on the safe side.

I, for one, would be interested to read the results when you go looking for someone to provide that service.

One of the issues with the material, and especially with the generation you are going to build and ride, is that
there seems to be no way to do that short of spending more money than your frame is worth for sophisticated
analysis........at least to my knowledge.

I could be wrong. Someone from the CF racing crowd should now post a link to such services.

And what does knowing that the bike snapped in half tell you?

The basic problem is that on one side you have folks with a vested interest in pretending that carbon bikes are rolling perfection. Those folks are usually either sellers of carbon stuff, or people who just spent ten grand on carbon stuff.

On the other side you have folks with a vested interest in pretending that carbon bikes are rolling deathtraps. These people are usually either sellers of steel stuff, or people who just spent ten grand on steel stuff.

There is actual information out there, but you have to look for it, and you have keep in mind that it doesn't conform well to the wishes of either group.

My point is that neither of the common stress related failure modes are represented by the common tensile test or compression test at a few mm/min head speed. For creep it is too fast. For impact it is too slow. It may represent other conditions for steel well, but not for most other materials. Why refer to something clearly not relevant.

Or you have people that have ridden all sorts of bikes for 40 years, own multipe bikes, including steel bikes, titanium bikes, aluminum bikes, and carbon fiber bikes, and have come to the clear conclusion, that CF is the best currently available material to make a road bike out of.

There's not an industry figure who beats the "ZOMG carbon is gonna asplode!" drum louder than GP. It's certainly understandable. Freds with money is a limited market and now that the majors have coopted his ideas and baked them into carbon Roubaixen and Domanen his interests are even more threatened than before.

Nobody is saying that.

And there's plenty of this. You're setting up a false equivalence.