bbeasley

Yup, I'm busted. Now back to discussing, what's really important, Assplosions.

sstorkel

Nobody on the planet designs carbon fiber frames that are going to fail just because they got knocked over. It simply does not happen. Ever. Anybody who tells you otherwise is full of sh*t. Lawyers have made sure that Engineers understand the consequences of piss-poor designs...

bigfred 

sstorkel, I agree with you on an awful lot. But, on this subject I'm going to respectfully beg to differ in some regard.

There are a wide range of fiber reinforced plastic frames available. Everything from entry level carbon that is heavier than one could achieve with aluminum and using realatively low modulus reinforcing fiber. On a few occassions I have even enquired of people who would know, "just how low a modulus is used in some of these frames? How would it compare with say a high grade 'glass' like S glass?" and they have always refrained from providing any sort of quantifiable anser. To some of the sub 800gram frames using realatively high modulus reinforcing fiber and as little of as necessary to fulfill the design requirements while be riden. But, which is in no way adequate to suffer a sidways impact from something as simple as being poorly balanced and falling over on a parking curb. Seen it happen and we could all identify the tone change in the carbon top tube with nothing more than our fingers, key from a pocket and an allen wrench from a saddle bag.

Of course, if that frame broke in use, the lawyers would be quick to point out it had been involved in an "incident" prior to the fateful ride. This is sort of what we're suspecting happened with my clubmate's frame. He bought it used from another club racer. To the best of anyones knowledge it hadn't been involved in any major accidents or been repaired in any way. However, it would have spent amost an entire season in the parking lots of race events and will undoubtedly have had other bikes leaned against it, possibly with their pedals contact the down tube, it may very well have been dropped and it rode around on the back of the mates car on a bumper mount. But, the weight bearing point of that mount is much closer to the seat tube than where the top tube fracture occured. And, it is/was quite a light frame.

I would be curious to know how many riders in this and other discussions like it have ever detected a damaged carbon part that had little or no outward sign of damage. I have. Those who followed my proportional crank build up thread will be familliar with the fact that a "donor bike" was used for some of the drivetrain components. I listed the donor frame on a local auction sight with a clear conscious, having already given it a good once over before purchasing. When time came to deliver it to the winner, I went to give it a good wipe and clean. In the process I noticed two very small cracks in the white paint on the inside of one fork leg. The cracks didn't not appear to even penetrate the clear coat and their was no real dark line to them or other insidious look about them. I suspected they were merely indicative of paint shrinkage or something. But, grabbed a screwdiver and gave a quick tap test. Low and behold there was quite a tone change in there vacinity. Anyone who has tap tested a fork will know that their tone does change considerably as you approach the drop outs and the carbon usually gets quite thick. However, in this instance I compared the first test to the other leg and there was no doubt that some degree of delamintion existed. It was that dead and hollow sounding. I was compelled to point this out to the prospective purchaser and was prepared to suffer a loss of sale. But, he was happy with the frame anyhow and drove away smiling. I wonder if that fork will survive, or, for how many miles. Will it provide any further indication that it has earned retirement before assploding? Don't know.

But, I believe that it had probably been involved in some sort of front end impact. I don't know if that was a collission, or hitting a curb or whatever. I believe that because the front wheel also had a bit of a 'hiccup' that I trued out and found that I couldn't get the spoke tension balanced to a standard I would normally accept. So, something had happened to the front end at some point.

I believe that designers are pretty good at designing components to meet their design criteria. But, when that criteria includes reducing weight below a certain point, durability and/or strenght has to be sacrificed to some degree. Brand new, off the show room floor, without having ever suffered an incident, nor accrued repetitive stress from the mass of a clyde, those parts should be fine. But, we don't live and ride on showroom floors and as soon as you roll the bike out the door it starts to accumulate a history. Generally speaking, the lighter the component realative to other like components the less tolerent it is going to be of smaller and smaller incidents. At some point, the simply accrued stress of being ridden by a clyde could be responsible for failure without other significant events. Seatposts, even aluminum, and saddle rails have been subject to this for years. There is a reason Thomson posts are so popular on this and other clyde forums:-) Having said that, I'm currently riding an Easton EC90SL carbon post on Bierwagen. IT FLEXES! A LOT! That makes it comfortable. But, it also concerns both me and my riding companions. So does the EC90SL fork I'm currently using. I'm watching both of them closely and am fully prepared to retire either if I see or hear the slightlest indication that they are suffering wear and tear. I've broken seatposts in the past. It can be really scary.

Anyhow. That's just my take on things. Others will no doubt see things differently.

bigfred 

About a year. Mileage unknown by me. I might be able to find out, but, I don't think 'mileage' is the concern. The bigger concerns are fiber modulus, quantity of fiber in thin sections (like the top tube) and accumulated or discreet but unnoticed events that may cause internal laminate issues that are largely obscured from exterior examination.

I don't know that hanging any bike by it's top tube is 'bad'. But, it came up as a topic of discussion after our mate's accident. He uses a hitch mount that attaches to a hitch ball and has a single 'clamp' on the top tube and which bounces around a bit on rough roads. He swears to have the clamp set very lightly, but, we all wonder about that. Like I said above the actual breakage wasn't immediately adjacent to that point. I think wheel or fork attachment for transport is probably the best bet for light carbon frames.

There are many different "Roubaix" frames and forks made from several different modulus' (or is the plural moduli?) of carbon. One thing this mate did was start riding a bike he could get an actual modulus number for. Many of the big brands(Trek, Specialized, et al) use proprietary names for their various grades of carbon. This prevents the consumer from knowing exactly what we are getting and making apples for apples comparisons between brands, frame weights, material involved, etc. And to a certain degree I can agree with this. Because, even given the modulus of the fiber involved there are a lot of other process that impact on frame strength, weight, stiffness and durability. Number of subassemblies, bladder types, pressure, temperature, resin, adhesives, etc.

If you really want to make an impact resistant frame, simply add a thin layer of kevlar to the exterior of the likely impact zones.

adrien

Am I on the right forum? This reads like escalating language more akin to the road forum. With that in mind, for the record I don't shave my legs.

To clarify (and repeat): I didn't say they would fail because they were knocked over. I said they could be weakened if knocked over, and furthermore that damage may be small but grow to the point of failure under stress. It may in fact be invisible (fork steerer, for example). It won't fail because it got knocked over. But it might be harmed in a way that is not easily visible and leads to big failure in the future. If I had one, I would be very fastidious with it because of that.

On the lawyer point, of course they aren't designed to spontaneously asplode. But I've also seen "previous damage" listed as reasons to deny warranty claims.

Finally, I actually like them, and some of them a whole lot. I just rode a Dogma for a week and it was wonderful, though $15k + is hard to justify. That said, when I get one, I'll buy one directly from a builder who will work with me on what I want, and part of what I want will be the highest possible performance without unnecessary weakening for practical use.

cyclist2000

I have a giant TCR with carbon seat post and carbon cranks, no problems. I have carbon cranks on a couple of bikes with out a problem. I have had these about 7 or 8 years. I have not tried carbon bars yet.

adrien

PS: any radically engineered bike will have compromises. Because of Carbon / epoxy's inherent lightness, those bikes tend to be highly engineered to a purpose. Marketing has driven this notion that lightness is everything, and compromised frames get ridden in a way that was never intended.

Some radically lightened steel bikes, for example, would likely not make good long-term Clyde bikes, either (something like an English).

adrien

If we're getting into parts, I've broken the right side carbon crank on two sets of Force. Was told by two mechanics not to ride carbon cranks.

sstorkel

Exactly! The problem is that you, and bigfred, don't seem to understand the compromises that go into creating a light-weight carbon fiber frame. In particular, you both seem convinced that lighter weight requires less durability. What you're forgetting is that there's a third variable than comes into the equation: money.

In most cases, you do not make a lighter carbon fiber frame by simply removing material and thus compromising durability. What typically happens is you spend more money! You buy a stronger carbon fiber fabric. Or you pay for a better resin. Or you pay for a more advanced manufacturing process. At the end of the day, you end up with a frame that's just as strong (or stronger!), but costs more to manufacture. As an example, just look at the Ridley Helium and Helium SL (= Super-Light). The SL frame is 200g lighter, (and $1100 more expensive) yet Ridley claims that laboratory testing shows the Super-Light frame is 8% stiffer at the bottom bracket, 4% stiffer at the head tube, and the fork has a 20% increase in side stiffness.

If nothing else, common sense should tell you that nobody is going to invest in a frame that becomes useless after the first parking lot tip-over. Luckily, carbon fiber is strong stuff and you'd don't have to baby it....

chriskmurray

8,000 feet of descending starting from 14,000 feet, almost all very rocky and technical on a full carbon (frame and fork with carbon steerer) and me weighing just over 200lbs and the bike was just fine. Carbon can be anything from super sketchy to surprisingly tough depending on how well it is built, same applies to metal bikes. The good news is like mentioned earlier, lawyers generally make sure a bike is tested well to make sure they do not have to worry about lawsuits from injury due to faulty product so truly bad carbon fiber bikes are pretty rare.

bigfred 

I'm not sure where to start with this. You're making so much less sense than I am accustomed to. But, here goes:

You are making the classic mistake of equating "strength" and "durability" as the same thing. They are not.

Higher modulus fibers are stiffer. They are harder. And, per weight they are stronger. However, because of the increased stiffness and hardness, they are less resistant to impact or bending beyond a reduced range compared to lower modulus fibers.

So, how does an engineer get a lighter frame out of the same mold. By moving to higher modulus reinforcing fibers. By using a material of higher modulus value the engineer can use less of that material to create the same strength or stiffness in the final product.

However, this does come with a reduction in the products ability to endure any non engineered for stresses. Like an impact to a top tube. There is less material in that zone and the material that is there is stiffer and more prone to impact related failure.

Strong, Stiff, Durable are not one in the same.

bigfred 

I would be willing to bet that frame weighs a wee bit more than 800 grams? Eh? Any chance it uses low'ish modulus fibers? If so, how low? Any black dyed glass fibers in it's build? Maybe an arimid layer in the down tube?

Can you anwer more than the first of those?

I've ask a few guys that can, and they've respectfully changed the subject.

sstorkel

If you think that carbon fiber needs babying, you should watch this video:

PinkBike Visits the Santa Cruz Test Lab

Start at the 5-minute mark if you want to see how a carbon fiber frame responds when it tips over into a curb

bigfred 

I thought you were of the reasonable group that recognizes that this isn't about the material but how it's used. No blanket statement in favor of or condemning any of the materials that bicycle frames are made from is going to be accurate.

I haven't clicked on your link, but, if its the one of them hammering an MTB downtube against the bench, aren't you attempting to compare apples to gorrillas?

chriskmurray

I will have to do the same, I work for the manufacturer of the bike I was riding and those are details I can not talk about. I can say it is a low 1,300 gram frame but in the fat bike world that is extremely light.

The Santa Cruz test video posted above was actually of Santa Crux running both the aluminum an carbon models of their Nomad through some of their normal battery of tests for frame strength.

bigfred 

Yeh, I've seen the Santa Cruz video before. The battering of the carbon frame is a bit misleading. And my historic reply has been to try that with a Storck Fascenario.

Anyhow. The OP asked about any instance of known CF breakages. And, there are plenty. However, there are also plenty of alloy and steel failure stories in this forum.

The real lesson is that folks need to shop realisticly and reasonably and monitor there equipment for signs of fatigue.

The materials arguement is simply a red hearing that rears it's head every time someone starts talking about failures involving CF.

I'm don't follow the fat tire world at all. So, have no idea about who's producing what sort of frames. And, don't get me wrong. There are plenty of quality carbon products out there. I would even hazard to say, most of them.

PSA: Fellow Clydes, just choose intelligently and monitor appropriately.

chriskmurray

I don't disagree really, it is simply about finding a well designed and executed product that fits your needs. I don't think rider weight specifically is a factor, but rather unrealistic expectations.

I am a full time wheel builder, both with my company and on the side and I deal with the unrealistic expectations thing often with my side business. People want a race wheel that is optimized for both climbing and aerodynamics and a wheel that is good for tens of thousands of miles of commuting. I can do any of the above easily, but not in the same set of wheels!

sstorkel

No, I was writing a quick post on an Internet forum rather than trying to be as precise as I would be in a Ph.D. dissertation. Sorry if you didn't realize that

If the only property an engineer was able to alter was the modulus of the carbon fiber used, I supposed you'd be right. Luckily, frame engineers don't have to labor under such artificial constraints. In the real world, an engineer would use carbon fiber fabrics of varying modulus (and orientation) to optimize strength, stiffness, durability, weight, and cost of the frame. They're also able to select a resin that is appropriate to the design, perhaps choosing a different resin for designs using higher-module CF than they would for a design using lower-modules fibers. A designer might also work closely with a manufacturing engineer to ensure that a design can be manufactured without needing excess carbon fiber or resin (ex: this video from Felt describes how they optimized the manufacturing of their top-of-the-line CF road frame).

And finally, despite the fact that you refuse to believe it, engineers do consider side-impacts when designing frames. Obviously, they don't optimize for side-impact survival but any designer who wants to keep his job cannot deliver a frame that's going to fail the first time the bike gets dropped. A design like that would put the manufacturer out of business between the massive number of warranty returns and the resulting lawsuits. Even a sub-800g frame needs to be able to survive side impacts! You can't win a race if your frame assplodes every time it gets jostled on the team bus...

FrenchFit 

Yawn... Torturing carbon frames v Al frames to failure in the Santa Cruz factory: https://www.youtube.com/watch?v=xreZdUBqpJs

Jarrett2

Well, I'm glad to hear there are so few first hand experiences that the thread devolved into semantic bickering.

That Santa Cruz video is wild.

TrojanHorse

Now ask if you should put clipless pedals on your bike and oh, how about a helmet?

bigfred 

Shall I describe how I lube my chains?

TrojanHorse

Only if you can tell me how you stopped your BB30 from squeaking.

bigfred 

No problem. I didn't buy one. All my bottom brackets thread into their respective shells. No squeaking, no premature bearing failures.

CliftonGK1

I have 2 bikes with CF forks, one of which is my SSCX race bike. I beat the hell out of that bike and the fork is still fine.
I work on plenty of CF bikes all day, from TT/Tri rigs to CX bikes to full carbon MTB race rigs. I've seen quite a few failures on parts and even on frames, but nothing along the lines of the catastrophic "asploded" failures which people worry about.
One of our shop's racers goes by the nickname Trainwreck. For real, the dude is prone to ruining equipment. Even after he admitted that he just plowed into a pothole at a tri in Chicago because he didn't see it when transitioning from the sunlight to the darkness under an overpass, his Zipp 808 didn't explode. The front end of his Speed Concept didn't splinter and murder him. He had a hairline fracture in his wheel, and that was it.
Someone brought in a bike with a damaged chainstay a few days ago. The damage was a straight up puncture to the stay, not from JRA, but obviously from an impact. The whole bike didn't shatter. Heck, the whole stay didn't shatter, for that matter.
I was on a ride with some pals, and one guy ripped his derailleur hanger off. The whole shebang goes and wraps itself up around and slammed the rd into the chainstay. There was a clean puncture, but the stay was intact.

I've only seen photo evidence of 'splody carbon, or heard stories about it from someone who knows a guy who has a friend who saw it happen.