nycphotography

Oh give me a break. Typical company town mentality right there.

noglider 

I'm glad Dengfu is sending you a complete replacement! Did they say how long it will take for you to receive it?

We're not privy to failure statistics, but is there an educated guess as to what fraction of failures are the dangerous kind? This one looks relatively safe, as opposed to, for example, the fork separating from the steerer tube.

I'm not opposed to buying a carbon frame for myself, but I haven't had one yet. These stories show me that the failure rate is a lot higher than those of metal frames, even though the risk level may be acceptable. I'm not so much worried about injury or death as I am about getting my money's worth. The dollars per year ratio seems to be a lot higher for carbon than for all kinds of metal frames.

f4rrest

Same mold.

PepeM

Same hands.

draganm

they should have , could have ,said something to that effect when I called, but didn't. They said" it's state banking regulations" total bull****, they are not a bank and certainly don't follow any regulations. The truth is they have no friggin idea why it's frozen, something done by an algorithm in software PP hired someone to write for them. Anyway, I'm done with it, it's ancient history and a technological dinosaur. Just a matter of time before we look back at PP the same way we see paying bills by licking a stamp. For those of you who use it , do NOT leave money in there and think twice, 3 times, about accepting very large payments thru them.
Rant off

good question, but it doesn't look like the type of damage you would get from clamping it in a stand. Looks like a failure from the type of bending moment you get from a rider bouncing in the saddle, in other words, normal seat tube loading.
I had a Trek Domane demonstrated to me at a shop, when the guy leaned on it , the seat tube flexed/bowed inwards towards the head tube in that approximate area. Maybe a little further down, but that bike was designed to do that

rpenmanparker 

Quite likely.

Grasschopper

Actually my thinking was that if it was clamped either just above that point or just below that point and held while force was applied either up or more likely down on the front end of the bike it could create a stress riser in that region. I've seen people building bikes and use the pivoting head of the repair stand by simply pulling up or pushing down the front end which could put some decent stress on the tube being held depending on how tight the pivot is.

This is actually why I decided to get the Park PRS-20 when I was shopping for a stand. And the few times I've used the repair stand on my Küat NV I don't clamp any tube...just use one side of the clamp as a cradle and the other side barely touching and just to hold the bike in place loosely.

nycphotography

1) put bike in stand, clamping to seat tube or top top.

2) spin up wheels and adjust gears.

3) grab rear brake

4) watch the momentum transfer into a torque at the clamp location!!

I tell everyone, don't clamp the tubes, and don't grab the brake, ease the brake on gently to slow the wheel. Oh, and I don't torque bottom brackets on the stand either.

67stang

it was never clamped there.

BillyD

cderalow

It's been done.

Not all frames are created equal. A look deep inside the carbon in counterfeit bikes | VeloNews.com

rpenmanparker 

Right, but we aren't talking about a counterfeit. Dengfu is a brand.

67stang

Good point.

Abe_Froman

Also, the article doesn't say what the real world differences are. For example, what is a tensile modulus test? Does it matter? Should I care about the discrepancy in PSI readings? Why?

Maelochs

Not surprised but quite gratified that Deng Fu is willing to stand by its warranty. I guess they realize that their name is all they have ... while Trek and Specialized know they can afford to deny legitimate warranty claims because their sales are so high.

Maelochs

This article was dissected at length in other threads back when it was new, and again every so often when it is brought up.

I see it basically as a PR piece designed to scare people into paying four times as much for a frame which won't be warrantied because the manufacturer is rich enough to laugh at claimants.

No one knows how many knock-off frames they sawed through to find the worst ones to make their points, or how many of their own frames they sawed through to find the best ones. No one knows if the whole piece is fact or fiction, or how much spin it contains.

No one argues that QC is Probably a lot more reliable at the really major factories ... but anecdote and observation seem to indicate that the better-known China-Direct dealers (many of which seem to use (I forget, what a dolt I am) I think it is FlyBike as a manufacturer)) seem to be holding up at least as well over time as the frames from the big brands (many of which likely come from the same factories and are likely made by the same workers, though not necessarily with the same post-production QC.)

Workswell in particular has video of its frames passing some very rigorous impact tests .... but are the test rigged? Who knows. But when a Specialized or Cervelo frame fails, the story doesn't spread in ripples through the online cycling community the way Chinabomb failures do (which used to be worse.)

No one knows if the knock-off frames, the Workswell/HongFu/DengFu/Flyxii frames are strong enough for the highest loads---or how the Giant, Trek, or Specialized or even Bianchi frames might fare---or if the tests have anything to do with real-world usage.

The lesson here seems to be that beyond all the hype, CF frames fail more frequently than any other kind, no matter what the source--but not with the kind of life-threatening "asplosions" people used to speak of. I have seen and heard about frames from all different makers, from the largest and richest to the boutique to the cheap Chinese, failing from collision and sometimes from general usage.

My takeaway is that CF is indeed more brittle than metal in many cycling applications, and people who want the CF benefits need to be realistic about potential CF drawbacks.

Meanwhile, I am planning the order of my second Workswell Chinabomb.

deepakvrao

My Deng Fu after I t-boned an idiot motor cyclist. Not sure if a 'regular' brand would have suffered the same degree of demolition.

67stang

Hi Deepak -
I'd lean towards the answer being yes - most carbon frames will break like that on a straight on impact. What is good to see is that the fork steerer tube looks intact.

Maelochs

I am amazed the frame broke and the front wheel looks fine.

Great thing there is the frame is probably the easiest and cheapest thing to replace and everything else looks perfect.

deepakvrao

Everything else looks perfect? Should have taken pics of myself

deepakvrao

What would that imply? The steerer tube being intact?

Reynolds 

Call me a retrogrouch, but I bought my steel frames cash-in-hand.

67stang

In my opinion only it suggests that the fork is built properly.

Without obviously knowing all the details of your accident, I am assuming that if you T-boned into something straight on with the bike, leading with the front wheel, that the force is directly on the fork and at the axle - the fork blades are now a significant lever against the head tube. Something has to give in this scenario and often you see the fork and steer tube separate in those accidents. In this case it appears the fork/steer tube held up and transferred the force to the frame, and it broke/separated at the top tube and downtube joints to the head tube. I'm not a frame builder, I have no idea if this is where/how you'd expect the failure. Because under normal riding conditions, hitting potholes and such, there is similar direction of force (but not magnitude) at the front axle, it to me is a good sign that the fork is built strong enough to take that load.

In any case, I have seen worse frame breaks from various accidents, and there is nothing specifically that I see here that says/shows the deng fu frame handling a crash any better or worse than others. Carbon frames will simply break somewhere in accidents like this, and steel/alum/ti frames will bend or break.

noglider 

It's quite common in a crash for only one of the frame or fork or wheel to be destroyed and the other two to remain totally intact. It's hard to predict which way a crash will leave a bike.

Maelochs

I guess I need to crash more often to gather more data.