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Old 08-21-11, 07:49 PM   #1
jimmyw
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carbon fiber failure- How durable is carbon fiber over bumps?

I've had a Quintana Roo cd01 for just over a year now and have been impressed with carbon fiber performance thus far. My only question is about the durability and likelihood of failure. I ask this because the other day, I decided to take a ride down a paved bike path and unknowingly went over a huge drop at the end of a bridge. I never hit a bump so hard and I'm concerned that it may weaken the frame internally. I didn't fall or anything, I just heard a load bang as may back wheel dropped. How likely is it that the force from impact traveled up my back wheel to my carbon frame causing internal damage? When I inspect my bike, I don't see any signs of cracks or anything and I didn't brake any spokes on my aluminum wheels either (they only went a little out of true which i quickly fixed). thanks

Jimmy
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Old 08-21-11, 07:59 PM   #2
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Old 08-21-11, 08:29 PM   #3
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Carbon fiber is very strong, obviously. What it doesn't do well is withstand cuts, scrapes and other abrasions that can lead to weakness and ultimately, failure. There is small likelihood that there is any "concealed" damage within the frame. Any damage would probably evidence itself on the exterior of the tubing.

So if everything looks pretty good from the outside, you should be fine. If there is any doubt whatsoever, take it to the LBS for a once-over.
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Old 08-21-11, 08:40 PM   #4
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I'm not a fan of carbon, but there's no denying how strong it is. My objection is that there's no reliable way of verifying the integrity of the construction or checking for shock damage.

However, in your shoes I wouldn't worry. The only high inertia part of your bike that might cause high stress on a bump is you. If you acted as the the hammer or dolly,to load the frame, your ass would have told you.

I'd be more conservative if the impact were to the fork because there's no safety net for fork failure. But frame or rear triangle failure (if it should happen) tends to have far lower consequences, so you can live with a higher risk level.

Meanwhile, keep an eye on it, look for any cracks or ripples, and listen for any sounds indicating movement of any kind.
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Old 08-21-11, 10:45 PM   #5
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How durable over bumps?, Real Bumps, for some portions of the day
The single day race, Paris to Roubaix , the Pro racers
after that one, have a new bike to ride the next weekend.
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Old 08-22-11, 07:41 AM   #6
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How durable over bumps?, Real Bumps, for some portions of the day
The single day race, Paris to Roubaix , the Pro racers
after that one, have a new bike to ride the next weekend.
I'm pretty sure the Teams don't discard their P-R bikes after one day. Other classics don't need the same level of "cush" so the P-R bikes are special but certainly not throwaways.
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Old 08-22-11, 07:53 AM   #7
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I'm pretty sure the Teams don't discard their P-R bikes after one day. Other classics don't need the same level of "cush" so the P-R bikes are special but certainly not throwaways.
I read something to the contrary. I'm not saying the bikes are literally thrown away after P-R, or maybe they are, but I remember reading that they are never raced again. And that's not the case with other races.
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Old 08-22-11, 08:54 AM   #8
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I read something to the contrary. I'm not saying the bikes are literally thrown away after P-R, or maybe they are, but I remember reading that they are never raced again. And that's not the case with other races.
I have zero knowledge about whether they change the bikes out or what they do with them if they do change them. But it seems plausible that the professional bikes might be built differently (i.e. lighter, thinner) to save as much weight as possible and therefore aren't as robust. Just a theory.
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Old 08-22-11, 09:01 AM   #9
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The P-R bikes are probably not thrown away because they would be unreliable, but because there are no other races on the pro tour that needs a similar bike, and they will almost always get a new bike the following year to show off new technologies.

It is quite likely they get sold or used for training for the rest of the season, not sawed up into bits to scavenge carbon.
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Old 08-22-11, 10:03 AM   #10
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If you have a general concern about carbon fiber and bumps, watch the Belgian Grand Prix (Formula 1) on August 28th,

The suspensions on every vehicle in the case is almost all carbon fiber. Just because they cab, Speed TV will show closeups of the suspension and front tire hitting curbs and bumps at speeds you'll never exceed on a bike.

From watching formula 1, it appears that carbon fiber is extremely strong - though it may be highly directional. About the only way they break carbon fiber struts in a Formula 1 race anymore is by running them into a wall or another car.

Your bike is clearly not built to the same specs, but watching a race may give you some confidence in the basic technology.
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Old 08-22-11, 10:32 AM   #11
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to scavenge carbon.
you cannot un catalyze cured epoxy..
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Old 08-22-11, 10:36 AM   #12
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The P-R bikes are probably not thrown away because they would be unreliable, but because there are no other races on the pro tour that needs a similar bike, and they will almost always get a new bike the following year to show off new technologies.

It is quite likely they get sold or used for training for the rest of the season, not sawed up into bits to scavenge carbon.
I don't remember where I read about it, if I find time I'll try to find it. What you say is true in that some of those bikes are unique for P-R, etc etc. But I brought it up in my earlier post because in what I read, the subject was how much abuse the bikes get in one P-R, and because of this they simply don't feel that the bikes are safe afterwards. Basically a lifetime of abuse in one day of racing. I mentioned it within the context of the thread.

In the case of the OP, I'm sure everything is okay. Keep in mind, too, that pros ride the lightest carbon usually, and there is more inherent concern with those than with most carbon bikes out there. We see carbon frames that have been bounced off of light poles, crashed into ditches, run head-on into other bikes, etc, and they just keep on ticking......... Wait, do I hear a tick coming from that carbon frame?
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Old 08-22-11, 03:44 PM   #13
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To see a carbon frame fail spectacularly, check that video link I posted earlier.
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Old 08-22-11, 04:05 PM   #14
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To see a carbon frame fail spectacularly, check that video link I posted earlier.
Everybody look at me! Why aren't you looking at me?!?!? LOOK AT ME!!!!!

Are you going to keep posting until someone finally responds? The OP isn't riding down the side of a mountain at 150mph.
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Old 08-22-11, 04:13 PM   #15
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If you have a general concern about carbon fiber and bumps, watch the Belgian Grand Prix (Formula 1) on August 28th,

The suspensions on every vehicle in the case is almost all carbon fiber. Just because they cab, Speed TV will show closeups of the suspension and front tire hitting curbs and bumps at speeds you'll never exceed on a bike.

From watching formula 1, it appears that carbon fiber is extremely strong - though it may be highly directional. About the only way they break carbon fiber struts in a Formula 1 race anymore is by running them into a wall or another car.

Your bike is clearly not built to the same specs, but watching a race may give you some confidence in the basic technology.
I agree, CF is very strong, but I think what worries some people is how they fail when they do reach their limits. CF parts tend to shatter and break up instantly at the point of failure, unlike steel which tends to yeild and bend quite a bit before total failure, so there is a bit of warning before failure. As for history of CF usage in FI cars, CF hasn't been perfect in F! car applications either. Wasn't it a CF suspension arm that mysteriously broke on Senna's car that made his car crash, penetrated his helmet's face shield and killed him some years ago? I know that one was an extreme case but it does show how engineers sometimes could not entirely predict how some materials might perform at most extreme conditions. If anything, CF is not as forgiving as steel when it comes to designing striuctural items to the "edge of the envelope". In the end, it all comes down to how an engineer uses the materials in his design and how he iunderstands the materials properties and behavior through its design service parameters.
Don't get me wrong, I love CF bikes I own a 1985 Vitus Carbone and I love the way it rides and performs. It's "only" 26 years old this year and I bet it's ready for another 26.
JMOs

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Old 08-22-11, 04:41 PM   #16
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you know they use carbon fiber in cars and motorbikes too and not only as cowling, but structurally too.
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Old 08-22-11, 07:16 PM   #17
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If you are worried about the durability of CF then best not ride on the new Boeing airliner.
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Old 08-22-11, 07:32 PM   #18
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If you are worried about the durability of CF then best not ride on the new Boeing airliner.
There's a difference between CF on bikes and on airplanes. Airplanes have highly controlled service and inspection protocols, where there's nothing comparable on a bike.
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Old 08-22-11, 07:42 PM   #19
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Wasn't it a CF suspension arm that mysteriously broke on Senna's car that made his car crash, penetrated his helmet's face shield and killed him some years ago?
I'm not 100% certain, but reasonably close to it, that F1 cars had carbon fiber monocoques but were still using steel suspensions back in 1994. Also, I think the going theory is that lowered tire pressures due to the safety car period lead to his car running too low and bottoming out, which essentially makes the spring rate infinite, leading to a complete loss of control, not suspension failure. However, you are correct that the suspension then penetrated his helmet and killed him, which I'm thinking is also less likely with carbon than it is with a steel spear.
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Old 08-22-11, 07:58 PM   #20
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Carbon vs steel failure rate at the shop I work for is 8 to 1. I started working there last September. That's enough for me to keep riding steel. I am not a pro racer anyhow, so I don't need that kind of ridiculous overkill. 99% of cyclists don't need it either, but it's what sells.,,,,BD

Oh, and.....

http://www.bustedcarbon.com/

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Old 08-22-11, 09:01 PM   #21
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And ...

http://www.youtube.com/watch?v=JLRDRzMWIsg#t=85s
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Old 08-23-11, 10:13 AM   #22
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Carbon frame + carbon rims + DH course = ??

http://www.youtube.com/watch?v=tVtg283HbRQ
http://www.youtube.com/watch?v=UxkX5EeFQys

No worries, mate!
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Old 08-23-11, 02:26 PM   #23
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I've had a Quintana Roo cd01 for just over a year now and have been impressed with carbon fiber performance thus far. My only question is about the durability and likelihood of failure. I ask this because the other day, I decided to take a ride down a paved bike path and unknowingly went over a huge drop at the end of a bridge. I never hit a bump so hard and I'm concerned that it may weaken the frame internally. I didn't fall or anything, I just heard a load bang as may back wheel dropped. How likely is it that the force from impact traveled up my back wheel to my carbon frame causing internal damage? When I inspect my bike, I don't see any signs of cracks or anything and I didn't brake any spokes on my aluminum wheels either (they only went a little out of true which i quickly fixed). thanks

Jimmy
Rule of Carbon – The carbon on your bike is not the same as carbon on a Ferrari F-1 car, is not the same carbon on a Boeing 787. The blanket term carbon needs to be used very carefully, as it encompasses all composites, much as the word steel encompasses all alloys, thereof.

Carbon composites (fiber) are pretty cool things, and they even make whole airplanes and satellite structures (yes, they do) out of the stuff. They are light, strong, can withstand ridiculous temperature variations, positive and negative atmospheres, and are moisture impervious. They do not, however, take stress loads very well.

While amazing stuff to work with, what has bothered us in the aerospace industry is sub-surface delaminations cannot be detected until a catastrophic failure of the structure. Think the American Airlines Airbus A300 in New York which shed its vertical stabilizer in-flight. Regardless of what “Officials” say about the First Officer stomping a rudder pedal (rudder hard-over), the real cause was delamination of the load bearing fin attachment points, which were all carbon composite. A host of other manufacturers use a Titanium/Carbon combination to insure lightness, strength, longevity, and most of all, serviceability. Our shop keeps a 1948 Cessna 140 as a parts fetcher/lunch wagon/play toy. I can rudder hard-over on it all day and the tail will not fail. Then again, it is made out of aluminum.

So, what does this have to do with bicycles? Well, the grade of composites used is good stuff, but is designed for a ground based vehicle, thus supreme strength and redundancy of load paths are not built in. They work well, do the job, and in many cases look awesome, but stress loads are not their forte. Now, the stress loads I refer to are compression, tension, torsional and bending loads. As a bicycle frame, the carbon will work fine. Ride the bike out of its design load and it will fail. This is where the quality of the carbon comes into play, and unless the company you bought it from tells you so, you have no idea where it came from or its grade.

I personally ride an aluminum frame, but that is due more to cost consideration then a fear of carbon. Carbon composites are damn cool things, and you can do a whole lot of things with them. My next bike will be carbon.

Bottom line, just keep an eye on your carbon bike for any viable damage, and by all means, avoid extreme loading conditions like Volkswagen sized pot holes, jumps from second story buildings and most of all, collisions with vehicles. With this in mind, a decent carbon component should last you a life time.

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