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  1. #1
    Senior Member Unagidon's Avatar
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    Carbon cross bike: anyone ever break/crack one?

    So many people claim - carbon road bike, fine. You're not going on any trails, less likely to crash, etc. etc. But for a CROSS BIKE, it has to be steel, ti or aluminum. Carbon - you're gonna crack the thing in two minutes.

    Well, I'm somewhat in love with the Ibis Hakkalugi, and yes, it's carbon. So, apart from just a gut feel that "plastic" is more brittle than metals, and not as "strong," has anyone ever actually experienced breaking a carbon cross bike? If so, did you break it in just a normal crash, or a crash that resulted in some broken bones with serious injury? And, if you weren't riding a carbon bike, do you think there would have been some damage - maybe a dent or worse - even if you were riding a metal bike?
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  2. #2
    Senior Member hocker's Avatar
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    Don't have a carbon cross bike, but a lot of people here in Colorado do. I've never heard of one breaking, at least not yet and I see a lot of X Nights and Scott RCs out there. The Hakkalugi is one sweet frame, definitely on my wish list. You could send an email to Greg from MudandCowbells.com as I know he and others on the Boulder Cycle Sport team have carbon frames.

  3. #3
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    My only data point is that when I hit a car quite fast last year, it was the aluminium part of my carbon/alu fork that snapped.

    CF is, in principle at least, ridiculously strong. Look at F1 cockpits and the testing they're put through for an example. But I guess it depends how it's applied to the specific case. Plenty must have been written about this though.
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  4. #4
    Yes, I have the memo. nickelbus's Avatar
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    I got one its as strong and stiff as ant Ti, steel or Alu frame. Also there are a fair amount of carbon fiber mountain bikes out there which take a lot more abuse than a cross bike.
    "Just remember, if you hang in there long enough, good things can happen in this world. I mean, look at me." - Tom Smykowski

  5. #5
    Senior Member
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    They make military aircraft and commercial passenger jets with carbon fiber and they are subjected to greater stress than bicycle frames. Carbon fiber is perfectly fine for cyclocross racing. Look at what the top riders are racing. The goal for all cycling equipment is strong and lightweight. Carbon fiber excels at that.
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    I race a Ridley X-Fire (2nd season on it) and have had no issues but have not really tested it with big crashes though do have a couple smaller ones. I have ridden it pretty hard though and it is still fine. For that matter so are my Reynolds carbon wheels.

    A couple of the locals have broken the Stevens carbon frames though. They seem to be built on the thinner/lighter side as compared to the Ridley.

    Mike

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    The only failure that I heard about the carbon frames was the early versions of the Specialized Tricross had problems with the derailleur tab. I guess they didn't use the bolt-on type and so a couple of Cal Giant riders broke off the tab and had to get another frame. Other than that, I haven't heard of a frame failure in the Norcal area.

  8. #8
    Mitcholo CrimsonKarter21's Avatar
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    It's not a 'cross bike, but I crashed my '09 Giant TCR Advanced headfirst into a turning rider at 35 mph. My shifter, bars, seat, both wheels, rear quick release skewer and helmet broke.

    My frame came away with a chip in the clearcoat. The fork was perfect, too.

    I raced that frame until September when I sold it.

  9. #9
    Senior Member hocker's Avatar
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    The rear brake mount on the Hakkalugi is pretty cool, and the Flanders symbol is a nice touch. The price isn't bad either for what you get.

  10. #10
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    Quote Originally Posted by stevage View Post
    CF is, in principle at least, ridiculously strong.
    No. That's not how materials work! There is no such thing as a single strength metric. Plus when a material is "strong" in a relevant way then less of it is used - that's how lightness is achieved.

    Look at F1 cockpits and the testing they're put through for an example.
    The concern with CF bikes is crash damage writing off an expensive frame after a comparatively low speed spill. This is almost irrelevant to F1.

    But I guess it depends how it's applied to the specific case. Plenty must have been written about this though.
    That's correct. CF is a great material in many ways - or rather it can be, because there is a lot of variation in the qualities of the CF tubing used - but it really is more susceptible to crash, and the failure mode really is a problem. I.e. CF can look fine and then CRACK! it's gone while in the same circumstances chromolly would be visibly dented but still perfectly safe to ride.

    Otoh - cross races take place (mostly) on soft ground. Even if crossers are crashed more frequently than road bikes, this has to count for something. Plus I'd argue that a catastrophic failure of a crosser frame is less serious than that of a road bike or MTB frame. I'd rather have a fork fail on me riding moderately sloping grass or gravel than on a car filled road or during a severe descent.
    Last edited by meanwhile; 11-03-09 at 12:22 PM.

  11. #11
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    Quote Originally Posted by pharding View Post
    They make military aircraft and commercial passenger jets with carbon fiber and they are subjected to greater stress than bicycle frames.
    This is voodoo science. Jets are not frequently crashed! But they are frequently inspected by professional engineers. And even a minor crash can impose more stress in a relevant dimension than an aircraft will ever take in flight.

    If you want to understand what cf is and isn't good for, then use the Internet the way it was meant to be used and do some actual research. Try reading this article - which I'll excerpt - in full:

    http://spokesmanbicycles.com/page.cfm?PageID=332

    Since carbon-fiber structures are not very fault tolerant (unlike metal structures), the design and execution plays an even more important role. And sometimes the fault is not in the design or execution of the structure - the fault may be a big rock coming in contact with the downtube. While the tube might not fail from such a large impact, the repercussions are usually hidden on the inside of the laminate, or within the laminate. Microcracks can then spread through the matrix, decreasing the ability of the fiber to transfer load. Metal tends to do a bit better in these situations - but you can make metal frames that break without warning, too...

    Now for the bad news: carbon's weak link is elongation. Elongation is your safety net, but with carbon it's low, low, low. Depending on lay-up, it's possible to get some elongation out of carbon. For example, there is a scissoring of layers in the 45-degree plies, but in general we're dealing with a material that doesn't have an overabundance of ductility. Composite designs are not meant to permanently bend. And when they fail, they fail all at once, so designers build in a big safety net. This is similar to what the aluminum designers do, in order to overcome the low elongation of that material.Most manufacturers are very secretive about their lay-ups, so getting good info isn't always easy. Reading through the Trek technical manual yields numbers for the specific modulus of that company's lay-up, which measures the modulus divided by the density. Backing these numbers out yields an 8 MSI modulus for the Trek OCLV lay-up.
    There are a lot of positives for carbon too - which the article also discusses. But an important part of riding a carbon bike safely is understanding the material and the greater seriousness with which you have to take the risk of crash damage, even no damage ia apparent to the naked eye. "But they use it for stealth bombers!!!" isn't really relevant. A bicycle is its own demanding engineering realm, not a subset of aviation engineering - assuming that anything "strong" enough for an aircraft can be adopted into a frame without thought is no more reasonable than assuming that anything ligh enough for tank armour would make a great frame too. Although a Chobham bike would have cachet...

  12. #12
    Carpe Diem bdcheung's Avatar
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    Quote Originally Posted by pharding View Post
    They make military aircraft and commercial passenger jets with carbon fiber and they are subjected to greater stress than bicycle frames.
    They make shopping carts out of steel and they are subjected to greater stress, and more frequent impacts with immovable objects, than bicycle frames.
    "When you are chewing the bars at the business end of a 90 mile road race you really dont care what gear you have hanging from your bike so long as it works."
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  13. #13
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    Quote Originally Posted by nickelbus View Post
    I got one its as strong and stiff as ant Ti, steel or Alu frame. Also there are a fair amount of carbon fiber mountain bikes out there which take a lot more abuse than a cross bike.
    The number of CF mtbs is TINY. I doubt if one MTB in a thousand is CF, precisely because of the risl of crash damage. Even at the high end only MTB in a hundred - probably a lot less - is carbon. Compare that with better than 50% of road bikes.

    Or look at:

    http://answers.yahoo.com/question/in...9213430AAK6xzA

    Carbon's weakness is damage.....you can scratch them up, but if you get any strong impacts or deep gouges, the frame is basically toast. (You can have some cracks/damage repaired, but it's very expensive and not usually worth doing it.)

    Several years ago, Trek did a warranty replacement for me on an aluminum Fuel 95 frame that cracked. Since they didn't have that frame anymore and refused to downgrade me to a cheaper frame, or upgrade me to the newer Fuel EX.....and this is odd.....they gave me a beautiful Top Fuel carbon fiber frame with a special finish. They didn't ask me or run it through the shop first....they just sent it.

    It was a beauty, and nimble and lightweight.....but on the third ride I laid the bike over in a rocky turn and put a big gouge with running cracks in the top tube. Trash. And, of course, with carbon fiber there basically is no warranty for damage.

    It actually takes quite a bit to fatally damage a carbon frame, but when you do, you'll find yourself shopping for a new frame. I think aluminum is the way to go for most mountain bikes.
    But again - I do think CF might make more sense for crossers than MTBs, because the ground that we (or at least *I*) tend to use them on is less rocky. Plus weight really counts if you're running with a bike. I'd just say - again - understand the material, consider the ground you use the bike on, how often you crash, how easily you can afford to replace the frame, what weight loss you might get and how much it will mean to you. If you're spending thousands of dollars a year on equipment and travelling to races anyway and riding an expensive lightweight frame that you will burnout in a couple of seasons, then risking a couple of grand on a CF frame that might move your race placings up even slightly could make a lot of sense, even if there is 1 chance in, say, 100 - or even 10 - that you'll lose the frame to crash damage.
    Last edited by meanwhile; 11-03-09 at 12:57 PM.

  14. #14
    Senior Member the pope's Avatar
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    my mind is buzzing from an informed and intelligent reply

  15. #15
    Senior Member hocker's Avatar
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    Quote Originally Posted by meanwhile View Post
    The concern with CF bikes is crash damage writing off an expensive frame after a comparatively low speed spill. .
    Actually, Calfee and others have had a lot of success fixing carbon frames, and some will argue that fixing a carbon frame is sometimes easier than steel/alu/ti because you don't have to replace a whole tube. There may be cases where you have to "write off" a carbon frame, but this isn't the rule.

  16. #16
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    Quote Originally Posted by hocker View Post
    Actually, Calfee and others have had a lot of success fixing carbon frames,
    That's VERY useful to know - thanks:

    http://www.calfeedesign.com/howtosendrepair.htm

    And in the UK

    http://www.fibre-lyte.co.uk/

    And I found a repair service and a home repair kit at:

    http://www.carbonology.com/repair-mo...8dc50fc4bf410f

    But that still leaves the problems of carbon damage being hard to spot by visual inspection, and of the dreaded catastrophic - ie sudden and total - failure mode. A set of guidelines and ideally tools to make inspecting would be really nice to have. Any suggestions?

  17. #17
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    ..And here's a thread reporting on the use of the repair kit:

    http://www.roadcyclinguk.com/forum/f...last=1&V=5&SP=

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