# Same experience with Easton forks?



## bahueh (May 11, 2004)

sadly, catastrophic failure of a new Easton fork last night on the local circuit...
don't know the rider, but am often at the venue..

http://www.cyclingrocks.com/viewer/2006_PIR/0821/crash/


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## AlexCad5 (Jan 2, 2005)

A previous crash is most likely the culprit.


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## 52-16SS (Dec 16, 2002)

Agree with Alex, I haven't seen a fork spontaneously fail that hadn't been in a previous crash. Would I swap my fork if I'd been in a crash? not unless it had any visual scars that would make me worried! If I did I'd have to get a couple of new bikes every year.


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## tigoat (Jun 6, 2006)

*crash*



bahueh said:


> sadly, catastrophic failure of a new Easton fork last night on the local circuit...
> don't know the rider, but am often at the venue..
> 
> http://www.cyclingrocks.com/viewer/2006_PIR/0821/crash/


It looks like the fork fail in the mid section, which usually a head on collision would have done it. The mid section of the fork is the least stressed area so it is unlikely that it fail from fatigue as result of normal use.


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## Mark McM (Jun 18, 2005)

*Carbon fatigue?*



tigoat said:


> It looks like the fork fail in the mid section, which usually a head on collision would have done it. The mid section of the fork is the least stressed area so it is unlikely that it fail from fatigue as result of normal use.


Why would a head on crash cause a failure in the mid section?

Where do carbon forks fail in fatigue? (And what is mechanism of fatigue in carbon?)


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## tigoat (Jun 6, 2006)

*stress and fatigue*



Mark McM said:


> Why would a head on crash cause a failure in the mid section?
> 
> Where do carbon forks fail in fatigue? (And what is mechanism of fatigue in carbon?)


Why not? Mount a frame with the front wheel off on a roof rack of a vehicle and then drive it into the garage.  

Carbon forks or any other fork for that matter would likely to fail where high stress is concentrated, which would probably be around the crown area. Mechanism of fatigue? In general fatigue failure will likely to be caused by stress from repeated bending load. A fork mounted on a bike is like a moment arm and if you keep flexing and bending it and eventually it will fail. Fatigue failure also can be caused by micro stress cracks, which sometimes can be difficult to detect until it fail. Fatigue analysis is a very complex engineering topic and it is difficult to describe it here without getting into the math.


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## Kerry Irons (Feb 25, 2002)

*Oh baby!*



tigoat said:


> Fatigue analysis is a very complex engineering topic and it is difficult to describe it here without getting into the math.


You just can't imagine how deep in the grease you are  I can't wait to watch this play out!


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## tigoat (Jun 6, 2006)

*cool!*



Kerry Irons said:


> You just can't imagine how deep in the grease you are  I can't wait to watch this play out!


Should I be nervous?


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## bahueh (May 11, 2004)

*Fatigue analysis =*



Kerry Irons said:


> You just can't imagine how deep in the grease you are  I can't wait to watch this play out!


bike fork impacts solid surface at low speed.
materiails is "fatigued"
rider gets on with his final sprint one day.
weight transfer into the direction of "fatigued" carbon
fork breaks.
rider hits head on pavement (I'm sure MarkMCM would say no way to prove helmet did anything to protect his head though).

there, no math.


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## Mark McM (Jun 18, 2005)

*Math?*



tigoat said:


> Why not? Mount a frame with the front wheel off on a roof rack of a vehicle and then drive it into the garage.  .


That's a very specific type of crash. Is it possible to damage the fork legs in their mid-span without direct impact on the fork?



tigoat said:


> Fatigue analysis is a very complex engineering topic and it is difficult to describe it here without getting into the math.


Why is math required? I am much better versed in metal fatigue than carbon fiber fatigue, but metal fatigue can easily be descibed without math.


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## Kerry Irons (Feb 25, 2002)

*Be afraid*



tigoat said:


> Should I be nervous?


Given that you have made some rather specious statements, and that Mark is a pretty good engineer who really knows his stuff, and now he is playing out some rope for you to get tangled in, yes, you should be afraid. You're going down, my friend.


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## tigoat (Jun 6, 2006)

*crash, fatigue, carbon fiber, metal*



Mark McM said:


> That's a very specific type of crash. Is it possible to damage the fork legs in their mid-span without direct impact on the fork?
> Why is math required? I am much better versed in metal fatigue than carbon fiber fatigue, but metal fatigue can easily be descibed without math.


How did you know that is a very specific type of crash? 

You can describe anything all day long but math is required if you are going to do any analysis. 

How verse are you with metal fatigue percentage wise compared to carbon fiber fatigue? Why would fatigue be different between metal and carbon fiber? How does metal fatigue work and what metal are you talking about? Please describe it in such terms so we can understand it.


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## tigoat (Jun 6, 2006)

*Who is this guy?*



Kerry Irons said:


> Given that you have made some rather specious statements, and that Mark is a pretty good engineer who really knows his stuff, and now he is playing out some rope for you to get tangled in, yes, you should be afraid. You're going down, my friend.


Why would my statements be specious? Could you clarify? Why should I be afraid of his engineering knowledge? Why would you want me to go down? Why would you want another cyclist who you don't know to go down? Going down means to loose? What is it that I have to loose? Are we having some sort of war going here? Did you offend you somewhere?


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## Mark McM (Jun 18, 2005)

tigoat said:


> How did you know that is a very specific type of crash?
> 
> You can describe anything all day long but math is required if you are going to do any analysis.
> 
> How verse are you with metal fatigue percentage wise compared to carbon fiber fatigue? Why would fatigue be different between metal and carbon fiber? How does metal fatigue work and what metal are you talking about? Please describe it in such terms so we can understand it.


This line of discussion sounds like you are just trying to avoid backing up your original statements. Why don't we get back to the matter at hand.

It is true that metal fork blades most typically fail near the blade/crown junction, or sometimes at the dropout - not surprising, as these are stress concentrating features. But carbon forks don't seem to have as regular a pattern for failure. I've seen carbon forks broken at a variety of locations, up and down the length of the blades. And not all of them have been run into garages. So how can you determine from the photos that it was not fatigue related?


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## tigoat (Jun 6, 2006)

*a pissing contest?*



Mark McM said:


> This line of discussion sounds like you are just trying to avoid backing up your original statements. Why don't we get back to the matter at hand.
> 
> It is true that metal fork blades most typically fail near the blade/crown junction, or sometimes at the dropout - not surprising, as these are stress concentrating features. But carbon forks don't seem to have as regular a pattern for failure. I've seen carbon forks broken at a variety of locations, up and down the length of the blades. And not all of them have been run into garages. So how can you determine from the photos that it was not fatigue related?


Avoid backing up my statements? Didn’t I explain adequately from my side of the story about your inquiry about fatigue? Would it be possible that the fork could fail from a head on collision on the side? Why not? Unless you want to get into pissing contest about engineering, failure, and fatigue, I don’t think there is nothing meaningful to debate bout on these photos. Also, unless you and I are there at the scene and have a chance to examine the failure in person, there is no way anyone can say for certain what would likely be the cause of the problem. Are you telling me that you can conclude what happened from the photos based on what you have seen from your previous experience? If you really were an engineer, you wouldn’t be a very good one, if that is the case. Where did I say for certain what happened in the photos? No, I cannot determine from the photos the cause of the failure. Let me examine the fork and then I might be able to come up with a failure scenario from an engineering stand point. With that, anything said here from the photos will be purely based on speculation and nothing else. :mad2:


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## Kerry Irons (Feb 25, 2002)

*Backing up?*



tigoat said:


> Avoid backing up my statements? Didn’t I explain adequately from my side of the story about your inquiry about fatigue?


So, do you have any clue how different the fatigue failure mechanism is between a plastic composite structure and a metal?


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## tigoat (Jun 6, 2006)

*what a joke!*



Kerry Irons said:


> So, do you have any clue how different the fatigue failure mechanism is between a plastic composite structure and a metal?


You ass boys are making me sick!


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## BShow (Jun 30, 2006)

Are there no warning signs of an overly fatigued carbon part? Fork, seatpost, stem, handlebars? 

Without really any knowledge of carbon fiber and its resistance to stress, it seems unlikely that sombody can be "just riding along"(be it in a race, training ride, spin around the parking lot) and the fork just snaps in half on both legs.


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## Insight Driver (Jan 27, 2006)

I see a pissing contest here. I looked at the pics for the second time. It occurs to me that you see the other biker holding his wheel. What if his wheel came out and in the sprint, pulled up on the handlebars, wheel comes out and forks hit the ground at speed. Seems if the fork failed the wheel would still be attached to dropouts.

Simple materials scienc: carbon composite structures do not suffer from fatigue failure mechanisms. They do, however, have failures caused by notch damage causing stress-risers and clamping damage if over-torqued. For point of fact, Easton takes 15 to 18 production forks at random and tests them to destruction. I have much more confidence with the quality of construction of Easton forks over the other brands.


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## Insight Driver (Jan 27, 2006)

bahueh said:


> sadly, catastrophic failure of a new Easton fork last night on the local circuit...
> don't know the rider, but am often at the venue..
> 
> http://www.cyclingrocks.com/viewer/2006_PIR/0821/crash/



How do you know it was a NEW Easton Fork? New as put on the bike for this particular race? New as you know the history of this bike and rider and it's a pristine fork that failed? Inquiring minds want to know.


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## SuperSlow (Feb 11, 2005)

its not a new fork it has silver dropouts


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## bahueh (May 11, 2004)

*must everyone be "right" on this forum?*



SuperSlow said:


> its not a new fork it has silver dropouts


this holier-than-thou thing is getting pretty old on this forum...

the rider told us it was about four months old...relatively NEW in terms of bike life. he's probably been racing on it all summer. With that, there was no mention of previous accident, contact, or collision...but whatever...point is, fork failure.


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## Mark McM (Jun 18, 2005)

*Loose skewer?*



Insight Driver said:


> I looked at the pics for the second time. It occurs to me that you see the other biker holding his wheel. What if his wheel came out and in the sprint, pulled up on the handlebars, wheel comes out and forks hit the ground at speed. Seems if the fork failed the wheel would still be attached to dropouts.


Upon looking at the photos again, I have to agree that this is the most likely explaination. If the forks had snapped, it seems likely that the fork ends would have remained attached to the hub (I've seen other broken forks where this was the case). In the second photo, the wheels is partially obscurred, but I can't see the fork legs near the hub. However, there is something on the road to the left of the rider that looks like it could be the missing left fork end. Finally, the close-up of the broken fork, the right fork end is still attached to the fork, and the drop-out appears to be completely intact, with none of the damage that one might expect from a hub/skewer being torn forcefully from the dropout.

Anecdotally, I was at a race this weekend where a racer on the start line was trying to tighten her front skewer. Unfortunately, she was turning the lever the wrong way, and no matter how she adjusted the skewer nut, she couldn't get the skewer to tighten down when closing the lever. After she stopped trying to adjust it, and appeared as if she thought it was "good enough", I finally stepped in and showed her the error she was making, and tightened down the skewer properly. I wonder if the racer in the photo didn't have a similar issue in improperly tightening his skewer.


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