Carbon Fibre frames are so weak...

[JonB]

https://www.pinkbike.com/video/243228/


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Be careful whose advice you buy, but, be patient with those who supply it. Advice is a form of nostalgia, dispensing it is a way of fishing the past from the disposal, wiping it off, painting over the ugly parts and recycling it for more than it?s worth.

[stinkwheel]

What would happen if you put your knee in the middle of the crossbar and pulled on either end?

It always struck me that the carbon was like a slightly stronger version of a cardboard tube in that it will support an enormous weight along its axis but will collapse if subjected to significant sideways force while under load.

None of those tests showed that. The "concrete block" test came closest but the members weren't under load.

I'd also be interested to see how it compares to steel. I wouldn't be any more likely buy an aluminium frame than a carbon one.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
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[JonB]

[stinkwheel]

I was being somewhat disingenuous in my criticism for the point of a discussion because I actually know very littel about carbon fibre (other than I really didn't like riding a carbon framed bike) but even so, they were careful to stress that frame only along its axis and only from the "working ends" of the frame.

It's like a longbow. Pull on the string and it will curve evenly from either end and the fibres in the wood will bend in unison giving it a massive amount of strength. Grab one limb halfway up and you could snap it between your hands.

I say it is, I don't actually know. I'm building a rigid mountain bike and I've passed over several carbon forks, mainly because I have no confidence in the material. Also because I want some flex in them. The carbon forks are all straight tubes and a tube is strong along it's long axis but weak to bending moments. The steel forks are curved and tapered, they just LOOK right.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[drzsta]

I wouldn't buy a carbon frame unless it was dirt cheap.

That splintering sound waaaay before it eventually snaps, that's irreversible damage.

[JonB]

[chris-red]

Road bike party was filmed using a bike with a carbon frame and he didn't break that.

I'm 18 stone and have a chinky Carbon Frame that has held my fat arse.
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[Seb]

Carbon frames and forks have come along a long way, most older stuff seemed more of a bullet point offering very little in the way of compliance or weight saving. My carbon road bike is a revelation compared to any alu frame I've borrowed or owned, the BB and chain stays are like an iron girder and I have to attack it like an ape to get the rims touching the brake pads on a climb, but yet it still manages to absorb bumps without jarring like Alu and without the weight of steel.

The gotcha of course is Carbon's longevity over consistent small hits. It's generally obvious when a Alu, Steel or Ti frame has had it's fill and is ready to let go, you get no such warning with Carbon. Ti is still king imo, but imperfections in the wielding are just as big a worry.
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2010 Triumph 1050 Sprint ST

[Kickstart]

[Rigga]

I wonder what grade of carbon fibre the frame was in the videos? I've been toying with the idea of a cf planet x bike but keep hearing stories about it been a low grade carbon fibre?
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Current bike: Honda CBR 1100xx

[sidewinder]

Does the strength of carbon also involve the type of weave to?

[carlosthejack...]

[AndyB1989]

Having seen several carbon fibre frames snapped (and way more ally ones snapped mind) Two were after Accidents involving cars and one a rider error accident with a wall.

The Accident with the wall was a planet x frame and comparing the quality of the carbon construction with the other two One from Giant and one from Merida the quality of the carbon construction was POOR on the planet x frame.

There are many different ways to lay up carbon and i think the nicest carbon road frames come from TIME because instead of being laid up as flat carbon into a mould they are woven into tubes that are then inflated before being impregnated with resin.

[Seb]

That's bladder molding and appears to be the norm despite what anyone's marketing says these days, you'll more likely find that the Giant and Meridia used a finer weave of carbon fibre and hence looked 'neater' when they failed due to the denser smaller strands.
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2010 Triumph 1050 Sprint ST