Disco Stu

A newbie friend said he'd heard that carbon frames become more flexible over time, so he asked me about it. Before I laughed it off and told him it was silly, I thought I should do a quick Google, and found this:

"Carbon-fiber components actually do get softer with use. As the component flexes, the internal fibers break free of the surrounding resin and delaminate invisibly. When TOUR magazine tested carbon forks, they found that after 100,000 test cycles, some forks had lost a significant amount of their stiffness. Today, the European Union standards for fatigue resistance specify how much stiffness a carbon component may lose over the test cycle."
https://janheine.wordpress.com/2012/0...es-going-soft/

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Adrianinkc

You're telling my massive guads are not responsible for the flex on my bike ?

cruiserhead

https://www.bikeforums.net/showthread...Fiber-Lifespan

mpath

Awesome...

Commodus

I've read that as well. I would guess that these standards should be available somewhere online, if someone would go and look for them.

laserfj

So your source is google and someone's blog?

StanSeven

That's right. This is BF and the 41. Everyone's opinion is based on blogs, speculation, and selective filtering of info and facts.

rebel1916

Jan Heine is a well known retro ******. Uh, I mean grouch. And you, of course,are a troll.

Commodus

He asked a question, he did not make an assertion. I'm not sure why he has to have better sources for that.

dstrong 

i would have thought CF becomes more brittle over time...hence the 'sploding.

merlinextraligh

This take from an Alpha Q engineer in Leonard Zinn's column may be a bit more objective. https://velonews.competitor.com/2011/...g-tools_181993

According to him, CF forks can lose up to 5% stiffness after thousands of cycles of high fatigue loading involving forces exceeding what is routinely encountered riding around.

And given that the CF frame is going to be stiffer to start, it's still going to be fine for years and years of riding. Pretty much a non issue as a practical matter.

bigbadwullf

Wow, you mean things wear out? Can't imagine that happening.

Seattle Forrest

You shouldn't be able to ask a question without citing references from a peer-reviewed science journal.

eippo1

Just when I get curious if things have changed and it's safe to post over here again, I come across this stuff...

cale

That would be awesome. Imagine bragging to your friends that your legs are so strong you actually tore the fibers apart and delaminated the frame. It makes me almost want to abuse my CF bike just to see if I can break it. Definitely worth the bragging rights.

Velo Vol 

Someone should blog about this.

ultraman6970

Fibers and all the glue they put in the carbon gets harder with time not softer. Steel for some reason does the opposite. As somebody said it should more brittle not softer.

RollCNY

Cake gets harder over time, while pie turns to mush. Clearly this must be relevant.

oldbobcat

In my experience with an '07 TCR Composite, this is true. Confirmed by a co-worker whose team was sponsored by Giant and a knowledgeable lady I met at a coffee stop. Her TCR Composite turned to mush over time, too. Symptoms were visible sagging of frame when I sat on it, increasingly sloppy handling, increasing susceptibility to speed wobble, increasingly difficult to control in crosswinds, and loss of sprint. Nanofiber and higher compression rates used in the better contemporary frames is supposed to address this.

Think about it. Carbon fiber and epoxy are inert. They can't change chemically, but stress can break them (in theory). I'm going with theory. And my own observation.

Regarding steel, I've heard that a well brazed joint actually gets harder with use.

rebel1916

Yes, steel is so real, that the harder you use it the stronger it gets.

Psimet2001 

This is fun.

Carbon frames are layers of fibers and resins. Over time small voids in the matrix can lead to "localized de-lamination" for lack of a better term. a broken fiber in a mesh of hundreds of thousands...yay. a hundred broken fibers at different points....thousands...over time if the construction techniques (molding and joint making) aren't well designed, thought out or executed they could lead to more microscopic voids or fiber breaks that would lead to a "softening" of the assembly.

In essence though - a non-issue for the vast majority of the frames and racers out there. The changes in layup techniques, frame shape, and resins account for large changes in the stiff "feel" of newer frames. Enough that it can be easy to get off of a frame from 3-5 years ago and get on a new one and mistakenly assume that the old one had "gone soft" because the difference in feel is just that drastic.

Disco Stu

I appreciate all the replies.
I don't know much about tech stuff, especially carbon.
I don't suppose anyone can find a link to the Tour Magazine test? I can't.

Disco Stu

Gee! Thanks. That's very interesting. I wouln't have guess it was that much

StephenH

I had just assumed that it was the riders getting fatter and weaker that was the issue, not that the bikes got weaker and flexier.

topflightpro

So I guess in a few years those big jets that are made of carbon fiber are going to start flapping their wings to take off?