Strength of Carbon Vs Aluminium for the doubters...

[VamP]

That looks like great fun

 

[Scruffmonster]

Say what you like... this has opened my eyes somewhat.

Cheers for posting.

 

[Rob3rt]

Unfortunately it doesn't always take the amount of force shown in the video to break, though. We've all seen the pictures of broken carbon steerers, handle bars, chain stays etc. Nasty stuff, and they haven't taken 1000+ lbs force as shown in this video.

Be that due to bad layup during manufacturing, cheapness, abuse, I don't know, but I believe it's still relevant.

It might not take as much force or impact as shown in this video (bare in mind these bikes are MTB's and are built to withstand harsh riding, a road bike will be less robust, but still not puny), however an uncompromised and well made (two criteria that should be considered regardless of material) carbon frame will take a hell of a force to fail outright, one that will result in a nasty incident regardless of material.

As for these broken steerers etc, well yes, shoot happens, steerers, chain stays and handlebars made from other materials also fail. Components such as handlebars in their alu form still generally fail suddenly and catastrophically as well.

I primarily ride an aluminium road bike (with carbon forks, I also have have an alu track bike with carbon forks and a full carbon TT bike), but would have few reservations about riding carbon day in day out. The reason I have not "upgraded" to a carbon frame on my road bike is simply because my alu frame is as light and stiff as most carbon frames within my budget.

 

[GrasB]

I think it's also worth considering how the frame breaks. Yes, carbon fibre is extremely strong, but when it fails it does so with a bang!

I fail to see how a carbon steerer suddenly giving is any advantage over a steel quill stem suddenly bending over 90 degrees... both dump you on the ground with 0 warning.

Unfortunately it doesn't always take the amount of force shown in the video to break, though. We've all seen the pictures of broken carbon steerers, handle bars, chain stays etc. Nasty stuff, and they haven't taken 1000+ lbs force as shown in this video.

I've seen broken aluminium, steel, titanium & carbon bike frames. Your point is?

 

[HovR]

It might not take as much force or impact as shown in this video (bare in mind these bikes are MTB's and are built to withstand harsh riding, a road bike will be less robust, but still not puny), however an uncompromised and well made (two criteria that should be considered regardless of material) carbon frame will take a hell of a force to fail outright, one that will result in a nasty incident regardless of material.

As for these broken steerers etc, well yes, s*** happens, steerers, chain stays and handlebars made from other materials also fail. Components such as handlebars in their alu form still generally fail suddenly and catastrophically as well.

I primarily ride an aluminium road bike (with carbon forks, I also have have an alu track bike with carbon forks and a full carbon TT bike), but would have few reservations about riding carbon day in day out. The reason I have not "upgraded" to a carbon frame on my road bike is simply because my alu frame is as light and stiff as most carbon frames within my budget.

All valid points - I like a well reasoned response.

I think the bold is a key factor - No one is arguing that carbon frames aren't extremely strong - but what leads to a carbon frame becoming compromised causing the kind of failures we see, and is it always fairly obvious to the owner upon inspection (such as a crack in steel/alu might be)? Is it due to abuse, the owners lack of knowledge regarding what a potential flaw in the carbon may look like, cheap/poor quality layup?

I guess one of the things I'm working from is the number of "My carbon frame suddenly snapped in half" type posts on the internet which I have come across far more than other materials, compared to the lesser number of threads on metal failures which tend to be on an older bike, and spotted early on as a crack.

Not the most scientific approach, I'll grant you, but I have yet to see a real world study of the longevity and durability of carbon bikes (if there is one I'd be interested to see it).

To clear the table, I'd also have no reservations riding a carbon bike day in, day out - I know many people do with no issues, I just like the security of a tried and tested metal frame where cracks can often be spotted before a potential failure.

I also like the idea that if I'm spending big money on a bike that it's an investment that will last me a life time (life time frame warranty anyone?)

 

[HovR]

I fail to see how a carbon steerer suddenly giving is any advantage over a steel quill stem suddenly bending over 90 degrees... both dump you on the ground with 0 warning.

Interesting, I've never seen the latter - Would be interested to perhaps see some images of a failure of this kind so I'd know where to inspect and check for fatigue.

I've seen broken aluminium, steel, titanium & carbon bike frames. Your point is?

My point was, exactly as I wrote, that it doesn't always take the amount of force shown in the video to break a carbon frame (for what ever reason).

I'm not arguing that other frame materials are perfect and don't break.

 

[RecordAceFromNew]

IMHO, when one can conduct a learned discussion on how to clamp a carbon frame on to a workstand or a car bike rack because otherwise it can be badly damaged, any debate on whether steel or carbon frame is more susceptible to damage becomes moot - who is to say some kid is not squeezing your carbon frame tubes with his fingers where you left it (or are we saying carbon bikes shouldn't be left out of sight?), let alone it being knocked/dropped/crashed as bikes do.

Sure extraordinarily thin walled alloy may buckle if squeezed, but the damage will at least be visible.

 

[Hacienda71]

Best thing to do is not to ride at all if you are worried about something breaking.....

 

[black'n'yellow]

who is to say some kid is not squeezing your carbon frame tubes with his fingers where you left it

do you really think that finger pressure would be enough to damage carbon tubes..?

 

[RecordAceFromNew]

do you really think that finger pressure would be enough to damage carbon tubes..?

I suspect it depends on the tube. I am pretty sure it won't damage the carbon tube of my Record seatpost (which is of course designed to be clamped, albeit with strict specification), but then at 200g it is about the same weight as some carbon forks including steerer, and over 20% of the weight of some complete frames!

The outstanding strength of carbon fibre is, shall we say, somewhat one*-dimensioned, which presumably is why lay up design and manufacturing are so critical.

For bikes an important durability issue is compared to metal how susceptible to cut and scratch resin/epoxy/fibre are.

* actually half, not one, because the fibre is strong only under tension, not compression

 

[NorthernSky]

cool, thanks
my carbon frame is going to last FOREVER! now i can never have an excuse to get a new bike

 

[Sittingduck]

Somebody should show the thread to the geezer from this vid. Something tells me he wouldn't approve

 

[Hacienda71]

cool, thanks
my carbon frame is going to last FOREVER! now i can never have an excuse to get a new bike

Yes, I have been telling SWMBO that I need to replace my carbon frame for a nice new shiney one every year or two. Now I am going to have to keep it if she reads this......

 

[musa]

carbon is weak..alloy steerer (but carbon fork)

 

[musa]

dental cavities
ass is gonna get bigger