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Australian Olympian

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Except in this case it was  3D printed titanium.

well now, more confusion, as this photo clearly shows the basebar in one piece. so i'm not sure what the material of the 'stem' that appears to have failed..

Very educational. I just assumed there was carbon fiber involved. I'll admit that I had no knowledge whatsoever that people are using 3d-printed titanium parts on bikes. Whichever, some exotic material failed really spectacularly.

Comments of this type about "carbon fiber" are almost always uninformed, and this one is. Carbon fiber-reinforced plastics and other composite materials are simply a (family of) materials that one designs for just as with any other material. It is not inherently more dangerous than, say, steel. Neither ie titanium, whether it is stamped, machined or 3D printed. 3D-printed metals are relatively new but they are no longer 'exotic', and titanium as a material certainly isn't.

Of course, any material can fail. But the ease of damaging carbon fiber, the particular ways in which it fails, and the difficulty in telling when it's going to fail make it an especially dangerous material for bicycles. A minor impact from a bike lock or coming hard off a curb off can fatally compromise carbon fiber. A small crack, dent or even scratch that would not affect a steel bike can lead to failures in carbon fiber parts. Also, damage and small fissures in carbon fiber can be hard to detect without some kind of ultrasonic scan. Worst of all, when carbon fiber does fail, it fails spectacularly. While other materials might bend, carbon fiber can shatter into pieces, as is evidenced by the carbon fiber debris field at the site of every crash in a bicycle race. The more bike parts made of carbon fiber, the greater chance of it shattering. Both because of faulty design and the inherent characteristics of the material, carbon fiber is a poor choice for most people who ride bicycles in the real world.

How do you say you're old and can't adapt to the changing times without saying you're old and can't adjust to the changing times?

This was a stupid post to start with and you are set to make it even dumber by just barfing up the same old bullshit everyone who doesn't like carbon spews when it comes time to pretend steel is better.

Materials are a tradeoff and yes, carbon has some undesirable characteristics compared to steel but it also has a weight/strength ratio that makes it worth the penalties to many people.  It is also infinetly more easily 'tuned' as a structure allowing bikes to be stiff where desired and compliant in other areas beyond what can be achieved with steel.

Crack doom steel, or any other material just as they do carbon.

You can find delamination and other issues without anything more complex than a pocket change.

The sort of impact that would "fatally compromise" a carbon structure would also compromise a steel bike of a comparable performance level; a dent in the butted section of a tube is absolutely a serious issue.

Yes, carbon can fail catastrophically but it also doesn't do it without any warning in most cases.  Steel, and especially aluminium, can also do the same thing. It's also worth mentioning that carbon is pretty simple to get repaired these days as well, often even easier than a steel frame and you cannot even really repair aluminium...


If carbon fibre was truly a material that could unexpectedly fail catastrophically with no warning and was difficult to determine the condition of do you think it would be used to such a high degree in aviation of high-level motorsports?  Both fields where strength and reliability are pretty important...

You don't like it, that's cool.  I personally prefer steel bikes myself for a variety of reasons.
But don't go around talking about it like it's inherently bad material when you obviously know very little about it.

So which specific statement that I made do you think are incorrect?

It's amazing how indignant you fans of carbon fiber get. 

I will tell you the specific statements you made that are incorrect:

     1. It does not take nearly the same impact or damage to destroy a carbon bike as a steel bike. A scratch or a jolt while falling over and carbon fiber can be compromised. So no, it does not take the same kind of impact to damage a steel bike. Not even close;

      2. The whole problem with carbon bikes is that yes, they do fail catastrophically, and without warning. They break in half. The seatposts splinter. The handlebars snap. Look at any crash in a biking event, like the two that happened at the beginning of the Tour de France this year. Pieces of carbon bikes are everywhere. Steel bikes do not break into pieces like that. Feel free to cite some examples. Not even the most hard-core carbon fiber lovers try to argue that carbon bikes can take a hit like steel bikes and survive.

     3. It's way harder to detect damage to a carbon frame than a steel frame. That's why you're supposed to have the dealer check them out or send them back to the manufacturer and have them checked out ultrasonically. Delamination is often hidden under paint. And yes, carbon fiber can be repaired, but a trustworthy professional repair is going to cost hundreds of dollars. Don't trust everything you see on YouTube. 

     4. The (partially) carbon fiber wings of airliners are constantly being checked by trained professionals for any signs of damage. They are also reinforced with different materials. Finally, they are not subject to the sharp impacts that bicycles are. When those happen, your carbon fiber wings break and everybody usually dies. In other words, there's no comparison to be made between an airplane wing and a bicycle. Motorsports is another area where pieces of carbon fiber shatter everywhere when there's a collision.

You make claims about carbon fiber that even its own manufacturers don't make, interesting. And could you point out where I said carbon fiber is a "bad material"? I just said it's not a material for most people who ride bikes in the real world. 

 

 

           

1. A steel bike can be damaged just by falling over but nothing is ever going to convince you of that so have fun there.

2. So wait, do they fail without warning or in a crash?  Because failure in a crash isn't a failure without warning.  Just because a steel bike doesn't break into pieces does not mean it survived the crash...

3. It is not hard to detect damage, you literally tap on it with a quarter and you can tell by tone if you have a crack or delamination. Repair is hundreds of dollars but have you checked into having a steel frame repaired lately? Because it is not exactly cheap either.

4. How often do you think that stuff really gets checked? That is the industry I came out of and I can tell you for a fact that it's not checked with the kind of frequency you seem to imagine.

I would say all the stuff you described earlier is implying it is a bad material.

I ride a bike with a carbon fork literally everyday, in the real world...

Jim, you just don't know what you're talking about, and I'd have to agree with Doug that you seem to largely be repeating talking points that you've read on the internet. My career as an engineer (BSME Georgia Tech, 1998) has been centered on things like technical problem-solving and vehicle evaluation, but I have studied the behavior of composite materials, I generally keep up on it, and I have designed and constructed composite components. Like other materials, fiber-reinforced composites are perfectly usable for 'real-world' cases if you design for the material and use normal safety factors.

Scratches on carbon fiber aren't a problem unless it gets through the top (protective) layer.  And a scratch that's goes through that layer is something that you're going to notice if you're riding or if you see it.

I think the best example of how tough carbon fiber on bikes are downhill bikes that have carbon fiber frames and wheels.  These bikes have been around for a long while and are pretty common for consumers.  We haven't seen a rash of carbon fiber failures on bikes bombing down a mountain at 30+mph while going through rock gardens and taking jumps.  If the average person can use one of those bikes for multiple years without problems, it's clear that carbon fiber can be used in other bike applications provided that they are designed and built properly.

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