Well, that’s a blow: Got a call back from UC Cyclery, where I’d dropped my bike off for a shakedown after my little car-vaulting excursion last weekend. It turns out that carbon fiber is susceptible to stress risers – bubbles in the frame – that can propagate over time into sudden, catastrophic failure modes. They’ve found flaws in the both the fork and the head tube, ugh:
Unlike steel and aluminum, which will both bend before breaking, carbon fiber just lets go. No warning, no flex, no visible cracks—just a loud crack and failure. The broken seatpost reminded us that more attention has to be paid when working and living with carbon fiber components. Budget extra time for assembly, read instructions carefully and be sure to use a torque wrench. If you scratch a carbon fiber bar, seatpost or stem (and we’re not only talking about crash damage; we’ve seen carbon bars scratched by a tie-down during transportation), trash it.
Thoughts of which would be enough to make your correspondent rather pensive on some of those steep downhills in the vicinity of North County, Coastal. Because Murphy is still on watch, and there’s just no way the head tube or fork would come apart just as he struggled to the top of Torrey Pines park, a-gasping and a-heaving at seven or eight miles per hour, no: They would have to give up the ghost at the bottom, doing thirty-five or so.
Which doesn’t sound like so very much, but really can make all the difference.
The good news is that Trek has a crash replacement program that will provide a new frame and fork at considerable discount. The bad news is that even with a discount, they’re not exactly giving them away, and there’s still labor to pay for. They’ve offered me a good guy discount for buying from there, but mechanics got to eat too.
It’s interesting that of the two carbon-based frames involved in last week’s mishap, the 45-year old one is healing day by day, while the one-year old one is headed for the scrap heap.
Still, count your blessings, yah? Could’ve been worse.
re carbon fiber: Wow, I had no idea. Another reason (aside from cashflow) that I’ll be sticking with aluminum.
I had a nasty crash earlier in the summer; the result of sprinting in worn out cleats to keep up with my dad on a climb (who is 55 years old and an enormously strong rider). Apparently it was quite dramatic – we had something of a paceline behind us, and everyone stopped to gawk. I landed well, spreading the impact over the entire side of my body and didn’t hit my head, so I didn’t break anything, but I did get pretty scraped up. Isn’t it amazing how your skin can be torn to shreads but the shorts over it aren’t even dirty?
Gee Lex. You had to ask about that to find out:
“carbon fiber is susceptible to stress risers”
LOL. You’ve been flying a carbon winged jet for over 20 years…surely you can risk riding on a carbon framed bike!
Good thing the taxpayer pays for new jets once in a while. Do you still have your Communion” money, too?
B2
B2 – in re carbon fiber jets, three words: Final. Flight. Control.
Conspicuous by their absence on road bikes.
And as for my communion money, sadly no: I blew it all on beer and hookers the following weekend. But that was a long time ago, and I was a very different little boy
B2 – as distasteful and painful as it probably is to use, at least a fighter jet has an ejection seat. The bike, not so much…
“…No warning, no flex, no visible cracks?
B2 – as distasteful and painful as it probably is to use, at least a fighter jet has an ejection seat. The bike, not so much…
“…No warning, no flex, no visible cracks—just a loud crack and failure…” Kinda sounds like how my 43 year old frame has operated for the past couple of years.
Lex – Glad to hear at least your 45 year old frame is recovering…
My 39 (almost) year old frame has plenty of cracks- but it has plenty of flex and curves too….
Glad you’re healing, and getting the bike fixed!
Thanks Kris. We all want Lex baby safe! Although I wouldn’t consider the t-handle a flight control!
I just find it funny that all them OTHER pilots (not Lex, of course) overstress their rides trying to win and don’t consider the effect much on their composite-components! Older, aluminum ribs sort of bend first.
F-18 wings, fishing rods, pole vaults, Corvettes, trek bikes- same-same on failure mode.
B2
Don’t forget carbon arrows. Pretty cool when the second arrow smacks the first one…of course you can’t hunt with it…
I once had a piece fail, the guys that were too macho to cower behind the protective screen got a very rude suprise as shards went wandering by.
>>>It turns out that carbon fiber is susceptible to stress risers – bubbles in the frame – that can propagate over time into sudden, catastrophic failure modes.
B2 – not being a pilot (I hate to fly at all actually), I can only imagine that the t-handle would be something any flyer would WANT to use. I’ve only seen video images of what happens; can’t imagine what that actually feels like.
Like going over the roof of a car and landing on the other side, possibly?
Kris,
I don’t know and I’ll (thankfully) never have to find out. I fingered it a cuppla times when things got hairy but I never had to use the final solution…Want and Need being 2 different things, of course!
Perhaps others who visit here can tell you what the sensation is. All mine have been simulations in the ejection trainer. I can tell you that those who accomplish the real thing have a clear memory of the experience broken doen in 20-30 millisecond increments and will usually regurgitate the story quite willingly.
I’m sure Lex has posted on the subject, as only Lex can in his archives.
B2
No, as I mentioned here recently, I’ve sat on a bunch of seats but never operationally checked any of them. All of my take-off’s and full-stops add up to a round number, which is a source of no small pride to your correspondent.
I know a bunch of guys who had to punch out, but I never envied them for it. I am told however, that no matter how bad the ejection is, it’s always better than submitting to certain death.
Which, it’s hard to argue with that.
B2 – glad it never got to that point for you. HAS to be a difficult decision…but as Lex says, choice of an interesting ride or no future, I guess the t-handle doesn’t look so bad after all.
Lex – round numbers in your world certainly sound like a good thing.
Oh, and my last post should have read “…the t-handle would be something any flyer WOULDN’T want to use…” wrong word and emphasis, apologies for any confusion.
Unfortunately on big new commercial jets like the A380 and the 787, there aren’t any ejection seats. Some of these guys are packing about 50% carbon fiber.
And as you say, there is no warning when the part is about to let go. No stress fractures, no test-to-destruction data. It just breaks.
Makes me a little nervous too.
Don’t worry, after two ejections you are back to round numbers again.