Just how fragile is carbon fibre?

biondino
biondino Posts: 5,990
edited July 2008 in Road beginners
We all hear that carbon bikes are more prone to catastrophic failure from knocks that would be barely noticed on a metal frame and damage that remains insidiously invisible until BAM, your ride shatters. But how true is this? How often do such things happen? How much is the manufacturers covering themselves? As a new owner of a carbon framed bike I want to find out as much as possible (i.e. facts, or at least informed opinion, not hearsay) about this subject and it would be great if people in the know provide info and links.

Thanks very much in advance!

Comments

  • Nuggs
    Nuggs Posts: 1,804
    I think the fact is that CF doesn't just disintegrate. The problem is that in the event of a big shunt, catastrophic damage may not be noticeable. This in turn may lead to riding a seriously damaged/weakened frame.

    It's certainly strong enough to cope with the average pothole etc...
  • andy_wrx
    andy_wrx Posts: 3,396
    CF is the most fragile material ever invented and if you so much as look at it in a funny way you'll have to bin the frame.
    Titanium's the answer.

    There, that's saved a dozen or so posts ! 8)
  • redddraggon
    redddraggon Posts: 10,862
    CFRP is brittle not fragile, this doesn't mean it's not very strong, brittle just means CFRP will fail via a low energy mechanism (i.e. v. little deformation).

    A knock that would write off a CFRP bike, would probably do the same to an Al-alloy bike.
    I like bikes...

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  • biondino
    biondino Posts: 5,990
    andy_wrx wrote:
    CF is the most fragile material ever invented and if you so much as look at it in a funny way you'll have to bin the frame.
    Titanium's the answer.

    There, that's saved a dozen or so posts ! 8)

    Haha! Funnily enough the reason I asked is because when me and two mates decided to do this charity ride, we all used it as an excuse to upgrade our bikes. So while they went from MTB/hybrid to £800 alloy bikes, I went from an alloy bike to a carbon monster, and they constantly take the piss about how a strong breeze will cause the frame to spontaneously combust etc.
  • topdude
    topdude Posts: 1,557
    Having just shortened my carbon steerer tube i decided to see how strong the waste bit of tube is.
    I put a 1cm section of the tube in a vice and tried to crush it across it's diameter. It deformed to an oval shape and with a lot of pressure started splitting shards off the inner surface. When the pressure was removed it sprang back to it's original shape and is still strong enough to resist deforming by hand. If that had been aluminium or steel it would be a flat bit of metal now :lol:
    I imagine the carbon tubes in a frame are quite a bit thinner so would not fare so well in a vice but i was impressed with the strength and resilience of it.
    I would say a carbon frame is a lot stronger than it feels and is no more likely to fail than any other frame material.
    However, i have a titanium frame just to be on the safe side :wink:
    He is not the messiah, he is a very naughty boy !!
  • andy_wrx
    andy_wrx Posts: 3,396
    We have been here before... 8)
    http://www.bikeradar.com/forums/viewtop ... t=12569354
    http://www.bikeradar.com/road/forums/vi ... t=12568629

    And there's an even worse one on CycleChat
    http://www.cyclechat.co.uk/forums/showt ... hp?t=14479
    - whole lot of 'I have a friend who says'-type bollox spoken here !
  • giant_man
    giant_man Posts: 6,878
    Oh for gods sake, such drivel being said in this thread.

    There is nothing wrong with carbon, it's a great frame material simple as that. And it's comfier over long distances than alloy or poss steel (wait for the barrage).

    It doesn't just collapse on you, and bits don't just break off. Yes if you do have a crash it will fail of course, but so will any bike tubing, but overall it's a wondrous material.

    Don't think it isn't strong when you tap it and you hear the hollow tubing, it's strong believe me!!
  • gkerr4
    gkerr4 Posts: 3,408
    topdude wrote:
    Having just shortened my carbon steerer tube i decided to see how strong the waste bit of tube is.
    I put a 1cm section of the tube in a vice and tried to crush it across it's diameter. It deformed to an oval shape and with a lot of pressure started splitting shards off the inner surface. When the pressure was removed it sprang back to it's original shape and is still strong enough to resist deforming by hand. If that had been aluminium or steel it would be a flat bit of metal now :lol:
    I imagine the carbon tubes in a frame are quite a bit thinner so would not fare so well in a vice but i was impressed with the strength and resilience of it.
    I would say a carbon frame is a lot stronger than it feels and is no more likely to fail than any other frame material.
    However, i have a titanium frame just to be on the safe side :wink:

    Yes - I did some "testing" on the top of a steerer tube too - it was enough to convince me that it is proper tough stuff!
  • Spinner28
    Spinner28 Posts: 58
    I've been using carbon bikes for a few years now, so far I haven't had any problems with them, and, touch wood won't, cos they're not cheap. I'm also on my 2nd carbon mtb. When I first bought a carbon mtb I admit that I was sceptical as to just how much stick a carbon mtb could stand?!! But was convinced at the time by a friend & by the fact that the demo bike performed so damn well. So if a carbon mtb can stand up the stick it gets, then I wouldn't worry about a road frame.

    A local LBS told me when I bought my first carbon road bike that carbon was a very delicate material & shouldn't be kept/ridden for any more than 18-months max with normal riding usage. This(apparently) is because carbon frames are designed for extreme performance in racing & wouldn't normally be kept for years & years, & unless I wanted to put my safety at risk I was recommended to trade it in, in 12-months(to be on the safe side you understand). Ok, so why then if a carbon frame is so delicate why would the bike shop be happy to put my well used bike on sale to someone in the quality used bike section?!!!!!! Wouldn't that be negligence? Or maybe they're genuinely worried about my safety, but couldn't care less bout anyone else out there?!!! :roll:
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  • gavmac
    gavmac Posts: 22
    As someone who has raced high performace dinghy's where carbon fibre has replaced metal alloys for masts and other tube type sections a good few years before it happened in bikes I would have little hesitation to switching. In the early days (about 10 years ago) breakages were more common but construction and bonding techniques have improved a lot and now that carbon fibre is almost exclusively used breakages are less common that the days when alloys were exclusively used. Contrary to what the uninitiated might think masts, bowsprits tillers, tiller extensions and all the other tube sections that are in use do suffer a fair bit of impact abuse. Early failures were mostly down to poor engineering and as these isues have been resolved reliability is very good. I'd probably go with one of the manufacturers with bigger R+D budgets for now though or who have been doing carbon fibre for a few years and avoid smaller manufacturerrs first or second attempts.
  • Belv
    Belv Posts: 866
    My understanding of carbon fibre is that it is very strong along specific lines of resistance. So doing whatever it was designed for it's fine but when it has a crash, for example, the CF is put under stresses it wasn't designed for and is more vulnerable than alloy.
  • il_principe
    il_principe Posts: 9,155
    FFS they make planes, boats and cars out of the stuff. It is very strong. My Pinarello Prince uses carbon that can take a pressure of 50 tonnes per square cm. The Airbus A400M has wings made of the stuff...
  • idaviesmoore
    idaviesmoore Posts: 557
    Your legs'll fall off before the carbon frame falls apart. The roads in a 45 mile radius where I live are like they've been taken from the Paris Roubaix and I've never had a problem in 10 years with a carbon frame. Exceptions are always around but as most people have said here......carbon's like garlic bread...it's the future :)
    'How can an opinion be bullsh1t?' High Fidelity
  • redddraggon
    redddraggon Posts: 10,862
    Your legs'll fall off before the carbon frame falls apart. The roads in a 45 mile radius where I live are like they've been taken from the Paris Roubaix

    Where am I going wrong? I've done most of my cycling in N. Wales and haven't found any decent stretches of cobbles yet........
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  • idaviesmoore
    idaviesmoore Posts: 557
    :lol: Try Harder!!!
    'How can an opinion be bullsh1t?' High Fidelity
  • synchronicity
    synchronicity Posts: 1,415
    Spinner28 wrote:
    A local LBS told me when I bought my first carbon road bike that carbon was a very delicate material & shouldn't be kept/ridden for any more than 18-months max with normal riding usage. This(apparently) is because carbon frames are designed for extreme performance in racing & wouldn't normally be kept for years & years, & unless I wanted to put my safety at risk I was recommended to trade it in, in 12-months(to be on the safe side you understand). Ok, so why then if a carbon frame is so delicate why would the bike shop be happy to put my well used bike on sale to someone in the quality used bike section?!!!!!! Wouldn't that be negligence? Or maybe they're genuinely worried about my safety, but couldn't care less bout anyone else out there?!!! :roll:

    What kind of rubbish place are you going to? :idea: Might I suggest finding another bke shop?
    They seem like all they want to do is make $$$. Some businesses care more about their reputation, then in turn more make more money out of that.

    I've had my beautiful Kestrel 500EMS since 2001, and there are riders around still on the old Kestrel 4000. That's nearly 2 decades...! :shock:
  • bahzob
    bahzob Posts: 2,195
    I posted thread re this a while backhttp://www.bikeradar.com/forums/viewtopic.php?t=12547276&highlight=carbon

    Pretty much came to conclusion carbon is every bit as strong as any other material and tougher than most.

    My personal experience: a Spec Roubaix bought start 2006 that has since:
    - done a 5000km solo tour of France + several more week/two weekers
    - Raids Pyreneen/Dolomite + lots of sportives 2006/2007/2008
    - Marmotte last week.
    - Been crashed (very badly) 3 times
    - total km to date around 30k

    Still looks/rides good as new.
    Martin S. Newbury RC
  • There is nothing wrong with carbon, it's a great frame material simple as that. And it's comfier over long distances than alloy or poss steel (wait for the barrage).

    and there we have carbon fibre myth number one. A carbon fibre frame is only comfy if the frame has been designed, and the carbon layered in a way, to make the frame comfy. For instance a Spesh Roubaix. A full on hardcore racing carbon fibre bike has very little extra comfort over an alu racing frame.

    Sorry but you were waiting for the barrage :lol::wink:

    As for strength issues if they were really that naff people just wouldn't buy them would they.
    Cycling - The pastime of spending large sums of money you don't really have on something you don't really need.
  • Mark Alexander
    Mark Alexander Posts: 2,277
    My Felt F4 has a disclaimer saying not to place on a roof rack with a brace at the down tube. Apparently it can crack from the inside :shock:
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  • andy_wrx
    andy_wrx Posts: 3,396
    My Felt F4 has a disclaimer saying not to place on a roof rack with a brace at the down tube. Apparently it can crack from the inside :shock:

    A brace at the downtube is basically a vice, yeah ?
    Would you put a bike tube made of any material in a vice and tighten it up really, really, really tight ?

    No, but I'll bet some f*ckwit will put their bike on their roofrack and be concerned about it blowing off and will do this.
    Do it on a carbon frame and you might crack it.
    Do it on a thinwall aluminium, steel or titanium frame and you'll put a dent impression of the clamp in it.
    A 25kg £59.99 MotorWorld-special MTB wouldn't mind, but I wouldn't like to do it on any lightweight high-performance bike and ride it afterwards.

    Felt's lawyers are putting this disclaimer on it in the way you get warnings on electrical items not to poke your fingers inside in case you get electrocuted.
  • penugent
    penugent Posts: 913
    I've been riding a CF for the last 3 years and love it - no problems.

    I agree with the poster who suggested that frame geometry has the greatest impact on comfort.
  • meagain
    meagain Posts: 2,331
    I doubt that any frame material would take as many impacts as the number of times this seemingly never-ending and totally non-resolvable topic has been aired.

    On and on and on....
    d.j.
    "Cancel my subscription to the resurrection."
  • de_sisti
    de_sisti Posts: 1,283
    edited July 2008
    Did you see that (Gerolsteiner?) rider in tour today whose bike was snapped in half after
    colliding with a street sign? I think he was riding a Specialized bike. (Nice bikes though).
  • richa
    richa Posts: 1,631
    It was a Specialized. Just snapped in half. That's Carbon Fibre for you :twisted:
    Rich
  • andy_wrx
    andy_wrx Posts: 3,396
    Oh Golly, I'll try to remember not to crash into street signs in future, because I ride a Spesh.

    I thought it was an OK thing to do :?