How robust are carbon frames?
Discussion
Hi all, my cube agree has been holed up over the winter and now the sun has come out I'm looking to get out and enjoy the roads again. Unfortunately last time I went out on it (November last year) I fell off...
My question is, how would any cracks manifest themselves? Are they easy to spot? To give you an idea, it was a low speed fall, front wheel slipped out on some railway lines. Am I worrying too much?
I should have taken it to the shop when I fell off, but I've been out of the country with work and unable to do so.
Cheers in advance
My question is, how would any cracks manifest themselves? Are they easy to spot? To give you an idea, it was a low speed fall, front wheel slipped out on some railway lines. Am I worrying too much?
I should have taken it to the shop when I fell off, but I've been out of the country with work and unable to do so.
Cheers in advance
Carbon frames are built in different ways, some are just a set of tubes created separately then bonded together. Some frames have the front triangle built as one piece, the chain stays and seat stays bonded together afterwards. Top end stuff like Look and Time are created as one section and they are ultra stiff as a result, the frames use long strands of carbon which run from the chain stays through the bike to the headtube and back.
If the frame has separate tubes bonded together cracks will commonly appear at the joints that take the most pressure, the top tube/headset or at the top tube/seat tube joint. Bottom Bracket areas are quite beefy so its rare a crack would appear there. Frames with minimalist seat stays (for comfort) may also have cracks but again its rare.
You do have to really punish a carbon frame to crack it. A lot of CX bikes are carbon, they use them in the Spring Classics and give them punishment. I cant recall seeing a frame crack for ages on a pro tour event. Some people are very unlucky and hit a pothole or something just as they are moving their weight onto the saddle or something but they are strong frames and wont generally crack.
Its hard to check on the joints as the frames are painted but just keep an eye on it all, you'd spot a crack so if you cant see anything its 99% fine, give it a good squeeze at the area of impact, listen out for any creaks which may be an indication however I've used mine throughout the winter and the roads I usually ride are dire, in short, stop worrying and ride it....
If the frame has separate tubes bonded together cracks will commonly appear at the joints that take the most pressure, the top tube/headset or at the top tube/seat tube joint. Bottom Bracket areas are quite beefy so its rare a crack would appear there. Frames with minimalist seat stays (for comfort) may also have cracks but again its rare.
You do have to really punish a carbon frame to crack it. A lot of CX bikes are carbon, they use them in the Spring Classics and give them punishment. I cant recall seeing a frame crack for ages on a pro tour event. Some people are very unlucky and hit a pothole or something just as they are moving their weight onto the saddle or something but they are strong frames and wont generally crack.
Its hard to check on the joints as the frames are painted but just keep an eye on it all, you'd spot a crack so if you cant see anything its 99% fine, give it a good squeeze at the area of impact, listen out for any creaks which may be an indication however I've used mine throughout the winter and the roads I usually ride are dire, in short, stop worrying and ride it....
Edited by anonymous-user on Saturday 27th April 15:10
ben_h100 said:
Hi all, my cube agree has been holed up over the winter and now the sun has come out I'm looking to get out and enjoy the roads again. Unfortunately last time I went out on it (November last year) I fell off...
My question is, how would any cracks manifest themselves? Are they easy to spot? To give you an idea, it was a low speed fall, front wheel slipped out on some railway lines. Am I worrying too much?
I should have taken it to the shop when I fell off, but I've been out of the country with work and unable to do so.
Cheers in advance
Low-speed fall? It'll be fine My question is, how would any cracks manifest themselves? Are they easy to spot? To give you an idea, it was a low speed fall, front wheel slipped out on some railway lines. Am I worrying too much?
I should have taken it to the shop when I fell off, but I've been out of the country with work and unable to do so.
Cheers in advance
I was knocked off last year, car hit me about 30 mph from behind, no obvious damage to bike and no 'contact' to bike either, in fact it was fine to cycle the 5 miles home.
It wasn't until the next day and the shock had worn off that I properly inspected the bike, on the top tube opposite side to which I was struck there was a one inch mark, not a crack per se but similar to what you get if you scuffed car paintwork.
Fortunately I have access to CF testing at work and they had a look at it for me, it hadn't delaminated but on microscopic inspection the fibres had cracked - game over
My theory is that the force created a shockwave and effectively cracked the carbon from inside, whether that is right or wrong I decided the frame wasn't safe to ride anymore.
It wasn't until the next day and the shock had worn off that I properly inspected the bike, on the top tube opposite side to which I was struck there was a one inch mark, not a crack per se but similar to what you get if you scuffed car paintwork.
Fortunately I have access to CF testing at work and they had a look at it for me, it hadn't delaminated but on microscopic inspection the fibres had cracked - game over
My theory is that the force created a shockwave and effectively cracked the carbon from inside, whether that is right or wrong I decided the frame wasn't safe to ride anymore.
TheFungle said:
I was knocked off last year, car hit me about 30 mph from behind, no obvious damage to bike and no 'contact' to bike either, in fact it was fine to cycle the 5 miles home.
It wasn't until the next day and the shock had worn off that I properly inspected the bike, on the top tube opposite side to which I was struck there was a one inch mark, not a crack per se but similar to what you get if you scuffed car paintwork.
Fortunately I have access to CF testing at work and they had a look at it for me, it hadn't delaminated but on microscopic inspection the fibres had cracked - game over
My theory is that the force created a shockwave and effectively cracked the carbon from inside, whether that is right or wrong I decided the frame wasn't safe to ride anymore.
Given what normally happens when a car tIt wasn't until the next day and the shock had worn off that I properly inspected the bike, on the top tube opposite side to which I was struck there was a one inch mark, not a crack per se but similar to what you get if you scuffed car paintwork.
Fortunately I have access to CF testing at work and they had a look at it for me, it hadn't delaminated but on microscopic inspection the fibres had cracked - game over
My theory is that the force created a shockwave and effectively cracked the carbon from inside, whether that is right or wrong I decided the frame wasn't safe to ride anymore.
ts something/someone at 30mph, how on earth did you or the bike emerge with no obvious damage, and indeed, ride 5 miles more?!Jimbo. said:
Given what normally happens when a car tts something/someone at 30mph, how on earth did you or the bike emerge with no obvious damage, and indeed, ride 5 miles more?!
It was more a 'push off' rather than 'knock off', I was moving to the centre in order to right turn, driver decided at this point to overtake, impact to me was half way along passenger wing so I in effect fell along the side of the car before hitting the deck once the car had 'passed'.ts something/someone at 30mph, how on earth did you or the bike emerge with no obvious damage, and indeed, ride 5 miles more?!Shock does funny things, thankfully I only had (soon to be very sore!) cuts & bruises and no other way of getting back.
Carbon is tricky.
As above people can fly around fields jumping and bouncing about with absolutely no trouble, they are extremely strong when loaded in the way they were designed.
But on the flipside you can knock a tool off the shelf in your garage and damage the frame to the point its worthless in a split second.
As above people can fly around fields jumping and bouncing about with absolutely no trouble, they are extremely strong when loaded in the way they were designed.
But on the flipside you can knock a tool off the shelf in your garage and damage the frame to the point its worthless in a split second.
Vladimir said:
I did a MatEng degree and while carbon can be ideal (road bike frames, bars, etc), I also think it's not a great idea for MTB frames, seat posts, etc. It has superb stiffness, is light, etc but any impact will cause serious problems.
So why do the manufacturers make them? And why isn't there a return pile the size of everest at the back doors of every top end bike shop?BadgerBenji said:
So why do the manufacturers make them? And why isn't there a return pile the size of everest at the back doors of every top end bike shop?
They stick so much resin on them that they do fare better than they could do but fundamentally, I just don't think it's the "right" material unless your sponsored and can replace frames without worries.There are a lot of incidents where they have failed fairly dramatically but like any material, it's a lot to do with HOW they are made rather than just WHAT they are made from. I personally am not keen despite being a bit of an MTB tart.
I was worried about the robustness of carbon when I recently parted with cash for the Colnago, so did quite a lot of reading to satisfy myself that it was not an expensive paper mache - which as it turns out it is!
I am no engineer, don't have a degree in resistant plastics so can only form an opinion from what I have read, but in a very condensed nutshell the layup of the carbon fiber, type and consistency of the resin, and method of forming the tubes play a huge part in determining the strength of the CF.
'Generally speaking' a well made CF frame is incredibly resilient due to the way it distributes shocks and load - as long as the shocks and load are applied to the frame as designed (which is why you will rarely see a cracked BB shell). However where CF does not perform well is when it takes a direct impact in a small area, or an area not designed to distribute shocks or load - which is why an innocuous bump in the garage when the bike falls over and catches the edge of the top tube on the workbench can cause a catastrophic failure of the tube. As far as I can tell from my reading it is very rare to find a crack on a frame from a direct impact, the force of the impact usually travels to the other side of the CF and causes internal de-lamination, the first the rider knows of it is when the frame is put under stress and snaps at the point of de-laminiation, this could be instantaneous to the shock, or take ages before it fails.
As a footnote I know someone who raced a Giant TCR and was hit side on by a deer while out training which put a hole in the seat-stay, he was able to ride home with no ill effects. He had the frame repaired and raced for another 2 seasons on it before he had enough money to upgrade to a newer bike.
I am no engineer, don't have a degree in resistant plastics so can only form an opinion from what I have read, but in a very condensed nutshell the layup of the carbon fiber, type and consistency of the resin, and method of forming the tubes play a huge part in determining the strength of the CF.
'Generally speaking' a well made CF frame is incredibly resilient due to the way it distributes shocks and load - as long as the shocks and load are applied to the frame as designed (which is why you will rarely see a cracked BB shell). However where CF does not perform well is when it takes a direct impact in a small area, or an area not designed to distribute shocks or load - which is why an innocuous bump in the garage when the bike falls over and catches the edge of the top tube on the workbench can cause a catastrophic failure of the tube. As far as I can tell from my reading it is very rare to find a crack on a frame from a direct impact, the force of the impact usually travels to the other side of the CF and causes internal de-lamination, the first the rider knows of it is when the frame is put under stress and snaps at the point of de-laminiation, this could be instantaneous to the shock, or take ages before it fails.
As a footnote I know someone who raced a Giant TCR and was hit side on by a deer while out training which put a hole in the seat-stay, he was able to ride home with no ill effects. He had the frame repaired and raced for another 2 seasons on it before he had enough money to upgrade to a newer bike.
MadDad said:
However where CF does not perform well is when it takes a direct impact in a small area
Worth a watch.http://www.youtube.com/watch?v=Y_O9PLorYPA
BadgerBenji said:
Worth a watch.
http://www.youtube.com/watch?v=Y_O9PLorYPA
Not the best representation: every time he thttp://www.youtube.com/watch?v=Y_O9PLorYPA
ts the forks with the hammer, it moves away (i.e. his arm absorbs some of the impact). A, ahem...rotund...STW reader clattering his frame/forks against against a hard, immobile object (tree/rock/the earth), however...BadgerBenji said:
MadDad said:
However where CF does not perform well is when it takes a direct impact in a small area
Worth a watch.http://www.youtube.com/watch?v=Y_O9PLorYPA
Either way, personally I love my new CF bike, it is responsive, quick, compliant and soaks up lots of road buzz!
BadgerBenji said:
Worth a watch.
http://www.youtube.com/watch?v=Y_O9PLorYPA
To me that's an advert for the metal forks.. He doesn't recommend using the carbon fork after that abuse, although it doesn't look badly damaged. The metal shows up the damage and so you know that there is damage.http://www.youtube.com/watch?v=Y_O9PLorYPA
I was concerned about this whilst buying a new bike in 2011.
I opted for a Cannondale Supersix, as it's covered by a lifetime guarantee.
I'm glad I did just that, as at the ripe old age of 13months the headtube cracked vertically, during last years CARTEN100. It was replaced under warranty.
One thing that concerns me is the ever worsening state of our cart tracks, sorry I mean "roads". A typical ride now is like 3hours riding on a vibrating ball bearings. No wonder frames give in. I would go for a lifetime guarantee, and nothing less.
I opted for a Cannondale Supersix, as it's covered by a lifetime guarantee.
I'm glad I did just that, as at the ripe old age of 13months the headtube cracked vertically, during last years CARTEN100. It was replaced under warranty.
One thing that concerns me is the ever worsening state of our cart tracks, sorry I mean "roads". A typical ride now is like 3hours riding on a vibrating ball bearings. No wonder frames give in. I would go for a lifetime guarantee, and nothing less.
russy01 said:
Carbon is tricky.
As above people can fly around fields jumping and bouncing about with absolutely no trouble, they are extremely strong when loaded in the way they were designed.
But on the flipside you can knock a tool off the shelf in your garage and damage the frame to the point its worthless in a split second.
A carbon frame that's loaded the right way can be very strong...As above people can fly around fields jumping and bouncing about with absolutely no trouble, they are extremely strong when loaded in the way they were designed.
But on the flipside you can knock a tool off the shelf in your garage and damage the frame to the point its worthless in a split second.
http://www.pinkbike.com/video/243228/
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