Sudden and Catastrophic Carbon Fork Failure

[Markjyost]

Here's my bike and the forks, at least what is left.

On Nov 21, 2013, I was traveling fairly slow (12-14 mph) commuting home on a relatively flat street. I've been riding this Litespeed Icon for five years, never in a crash, never saw any stress fractures in the carbon fiber fork.

I recall hearing a crunching sound, I saw my wheel coming by on the right, then I face planted. The bottom of one fork is undamaged, the bottom of the other has a slight crack on the base. Both are sheered off.

Never lost consciousness, but trip to the ER. Major facial road rash, headaches stopped after two days, rotator cuff strain. I think I was lucky but am wigged out about fast descents, particularly in the mountains.

Any comments?

 

[alienator]

Here's my bike and the forks, at least what is left.  On Nov 21, 2013, I was traveling fairly slow (12-14 mph) commuting home on a relatively flat street.  I've been riding this Litespeed Icon for five years, never in a crash, never saw any stress fractures in the carbon fiber fork. I recall hearing a crunching sound, I saw my wheel coming by on the right, then I face planted.  The bottom of one fork is undamaged, the bottom of the other has a slight crack on the base.  Both are sheered off.    Never lost consciousness, but trip to the ER.  Major facial road rash, headaches stopped after two days, rotator cuff strain.  I think I was lucky but am wigged out about fast descents, particularly in the mountains. Any comments?

Wow. I'd say you're lucky to have gotten away with the injuries you sustained. Your injuries could have been much worse. I don't know what can be inferred about the fork failure and its cause. Did your front wheel suffer any damage?

 

[Markjyost]

I think I'm very lucky, particularly since in another block I would have been descending at 25 mph. And I often ride this bike in the mountains, which is even scarier.

No damage to the wheel that I can see, a Mavic Aksyum. It was free from the remnants of both forks when I picked up the debris off the street.

I initially assumed it was QR failure, but then I'd expect damage to the bottom of both forks. Only one is damaged, which indicates to me it didn't hit the street like it would have if the wheel popped off.

But I'd be more comforted if it were a loose QR rather than carbon failure.

 

[alienator]

Have you tried to contact Litespeed? Even on a 5 year old CF fork, a failure such as yours is not the norm.

 

[CAMPYBOB]

"No damage to the wheel that I can see, a Mavic Aksyum. It was free from the remnants of both forks when I picked up the debris off the street."

Were the two lower sections of the fork blades still clamped to the hub by the quick release when you retrieved the front wheel OR did you pick up the wheel and the two lower sections of the fork blades separately...i.e. three separate pieces laying in the road?

You just made it sound like you retrieved three separate pieces. If that is the case, my guess would be that the QR failed; did not have enough closing pressure and either the wheel slipped free of the dropouts or the QR lever vibrated open or...when you closed your QR the cupped washer under the lever cam was 90° out of phase and vibrated to the correct position, thereby reducing the locking tension. 'Open' style QR's have been known to have that last explanation occur.

If the wheel was still firmly gripping the lower fork blade stubs...that is classic fork failure mode.

 

[Markjyost]

Three pieces, all separate. In a sense, I would feel better if it was the QR. I would have more control over it in the future.

But wouldn't both of the forks been damaged on the bottom in that situation? Only one was, suggesting to me that one fork failed and the other was ripped off in the aftermath.

Thanks!

 

[alienator]

Three pieces, all separate.  In a sense, I would feel better if it was the QR.  I would have more control over it in the future.  But wouldn't both of the forks been damaged on the bottom in that situation?  Only one was, suggesting to me that one fork failed and the other was ripped off in the aftermath. Thanks!

Not necessarily. If the wheel twisted a loose or open QR from one dropout, it could possibly have put enough torque on the remaining fork leg to snap it off. Did your fork dropouts still have the lawyer lips on 'em?

 

[CAMPYBOB]

"But wouldn't both of the forks been damaged on the bottom in that situation? Only one was, suggesting to me that one fork failed and the other was ripped off in the aftermath."

Not necessarily. It is possible that you were falling off to one side as either the fork failed on one side before the other blade failed OR as your wheel came loose from the fork you came down more to one side as opposed to a straight forward fall.

It seems your QR was loose or failed as during most fork blade failures the broken stubs stay attached to the hub. Think of the force necessary to pull a 6"-8" fork blade stub from a properly tightened QR.

Now...if there was only a dropout left attached to the hub and the carbon blade was broken off at the dropout, that would point to fork failure...firstly the fatigue/over-stressed break at the upper separation area and secondly an impact separation at the dropout.