patentcad

...is amazing at times. Yesterday in Prospect Park (circuit race in Brooklyn NY), I'm carrying my Cervelo back to the car (I had punctured with 3 laps to go and didn't want to ride the flat tire on my Zipp any further). I see another guy doing this with a new Trek Madone. His rear chain stay was cracked. How did this occur I ask.

He's riding up the 3-4% Col du Prospect in the 5 race, maybe going 18 mph (or whatever speed they go over that rise at) and a guy behind him runs into the back of his Trek. So how fast was that impact? 2-3 mph? They were going in the same direction on an upgrade. Neither of them fell over. His wheel starts rubbing. His chain stay is cracked.

CF is certainly the best frame material from a performance standpoint, but it sure breaks when you crash it. Even when you bump it sometimes.

He was bummed. His bike was only six months old, beautiful ride. I wonder what Trek's crash replacement program is.

Soil_Sampler

it is great stuff until/if it fails.

Grumpy McTrumpy

Just because he said it went a certain way doesn't mean it actually did. He might have squeezed the brakes at the wrong time. The chainstay might have already been weakened from a previous impact.

lung

I love my CF bike. But if/when it dies... I will go back to titanium. I never had to worry about it... and an hour with a scotch brite pad makes it look like new. But for now... my carbon frame is amazing.

DaveSSS 

I've owned two Colnago and four LOOK carbon frames since 2000. I've been down six times while riding these frames, including two car/bike accidents and none of the crashes caused any damage to the frames. My 2004 LOOK KG461 has been through two slideouts and one car/bike accident - all without a scratch on the frame.

BillyD

You blasphemous heathen . . . how DARE you cast dispersion on the almighty, great, indestructible carbon fiber!!!!!

Don't you realize that any and every other bike material is JUST as fragile?? How do I know? Well, a bunch of guys around here have been saying that for years, no?

SpongeDad

Not sure what that means. That he touched the brakes and caused the impact? Or that touching the brakes put stress on the frame, causing the crack?

rdtompki

A climbing situation probably represents the highest compression load on the chainstays. They simply weren't designed for the combination of loads (additional impact load). I think this is more of a problem with buyer expectation than design. Maybe titanium is a better frame material at some price, but racers and others driven to high performance/low weight will still cause frame manufacturers to design out the margin that enables these frames to survive these mishaps.

Matt Gaunt

A friend and I recently did some fairly unscientific strength tests on some CF tubing he had lying around. Essentially, vicing it up at various points and either leveraging it or just crushing it with the vice to destruction.

It is amazingly strong in some directions and fairly unimpressive in others. Even so, from the guy with the Trek's story, I would say something else must have contributed to that failure other than the 2-3mph impact described by Pcad.

FlashUNC

How does this story dovetail with your theory that everything breaks, pcad?

Grumpy McTrumpy

By squeezing the brakes at the wrong time he could have set up a situation where the impact speed was far greater than just 2 MPH. Having been behind someone on a climb who locked up his brakes (bringing both of us down) I can say that sometimes people freak out and really brake hard. He may not "remember" it that way.

Drag

The Force is strong with this one...

Jynx

Please elaborate. I am very curious.

jdon

I am sure all you NY riders remember the Airbus that crashed in Queens a few years back. CF tail came apart. CF is great when you are moving in the designed fashion. Add a side load or an impact and she comes apart pretty good.

Fixitman

La la la la la la la la Just bought a full carbon bike .. not listining.

rc51crazy

i'm following this discussion closely..considering a new bike purchase ( the ol' steel steed is getting old) and can't decide between the Ti or CF frames. So i'm reading as much as i can on both, to help make my decision ... soooo.. carry on

BillyD

Frunkin

I've seen so many carbon bikes crashed, and immediately hopped back on without a second thought that I'm really not too worried about it. When you watch the way some people treat and race their bikes, you realize that a lot of people buy into the "carbon explosion" wayy too much.

dgasmd

Well, from looking at some of the crashes in the pro peloton, you would think carbon fiber is the Ultimate Indestructible Material. Everything fails at some point I guess..............

patentcad

Oh stop Grumpy.

Doohickie

I'm an engineer, and a product should be designed for the way it will be used. If it is to be used for racing, and a little bumping is not unheard of, it should be designed for that exact combination of loads.

DESIGN FAIL.

patentcad

It's worth it. Nothing beats CF in the performance dept.

You don't see any pros on anything else these days do you? Let that be your guide.

Doohickie

When the directions of loads are known with a good amount of certainty, carbon fiber excels because the carbon fibers can be arranged to handle the loads in those directions and the composite material (carbon fibers plus resin matrix) can be tailored to the loads. By their very nature, composite materials are orthotropic- tailored to take loads in certain directions, as opposed to isotropic- having the same mechanical properties in all directions.

So if you used a composite bike for a spin bike, it would last forever, because the loading would be very uniform and predictable. But out in the real world, you don't have that kind of control on how, exactly, your CF bike frame will be mechanically loaded.

mtnroadie

I am also an archer. I shoot carbon arrows at nearly 300fps, often hitting one with another, and seldom ever break one. I can't believe that the carbon fiber bikes are any weaker.

Brian Ratliff

Lightest, stiffest material you can find to build bike frames out of. Name any metal bike and I'll name a CF bike that is both stiffer and lighter.

Everything is built for a purpose. If you want an indestructible race bike, go with my steel, 21lb crit bike I have built up. If you want the lightest climbing bike, then you will have to deal with the fact it's not going to take crashing very well. It is a marketing fail if anything. The engineers did their job.

Besides, it's likely that this story isn't complete.