Carbon fork question

[CNY rider]

Last summer, out riding my Hors with an Easton all carbon fork, JRA you know :) and maybe not paying attention for just a second. WHACK, direct hit on a nice pothole. Was able to stay upright but heard a very loud snapping sound from the front end. Was sure I was going to be left holding snapped handlebars or a sheared fork steerer. Did a quick once over, it all looked and felt Ok and managed to gently get back home.
Pulled the fork out, looked it over and found nothing wrong. Same with the bars. Rode the Hors maybe 5 more times last summer, had no problems.

That incident still bothers me though and has left me uncomfortable with the fork. So yesterday I again pulled the fork (because really, once you've skiied a couple of hours and the wind chill is way below zero what else are you gonna do but go to the basement and play with your bicycles?) and I have been over every mm of it. Nothing I see wrong with the steerer, no cracks in the clear coat. It all looks just fine. I wonder though if there can be a structural problem that is not visible with the naked eye and if I'm at risk of some sudden catastrophic failure happening due to damage I can't see.

Anyone with experience with this kind of thing?

I'll also add that I grabbed a Pro by Shimano fork with aluminum steerer off bonktown yesterday just in case. :) Anyone have one?

[Lifelover]

I'm not a carbon expert but I play one on the internet.

ATMO, there is very little chance that an external impact would cause a failure that can only be seen internally.

However, if you have lost confidence in the fork you should probably replace it. Riding should be about de-stressing.

[SamIAm]

I had a similar incident where I hit a large pothole and heard a disarming cracking noise. Now I had a steel fork, but I never understood what made that noise until about 2 months later when I noticed that the handlebars had rotated down a bit relative to their normal position. I ultimately attributed the noise to that.

[Dave]

Most likely the sound was from a loose integrated headset. If the bearings are not adjusted to be as tight as possible without actually restricting the fork from self-centering, then a bit hit will create a nasty noise. Buying a new fork was a waste.

A hit that's hard enough to break a fork would usually render wheel unrideable first.

[David Kirk]

There a few things that could make the noise......... like others said a headset shifting in the frame, a fork crown race shifting on the fork, a handlebar rotating in the stem.. etc.

The fork is probably fine. That's small conciliation if you approach the bike with skepticism each time you head out for a ride or if you wince at every crack in the pavement. Like was said before, if you feel nervous about the fork you should replace it with something you feel better about. This is supposed to be fun and when it's not it doesn't make much sense.

Dave

[1centaur]

I have heard nasty noises from sharp hits but it really was something to do with the fork/headset junction adjustment, not the fork. I agree with others here - you have inspected it as well as it needs to be inspected, and it's fine.

[regularguy412]

Most likely the sound was from a loose integrated headset. If the bearings are not adjusted to be as tight as possible without actually restricting the fork from self-centering, then a bit hit will create a nasty noise. Buying a new fork was a waste.

A hit that's hard enough to break a fork would usually render wheel unrideable first.

+1 on this assessment.

I had a similar incident to the one you described - going fast, on the hoods, went through a railroad crossing that had developed a bump on the far side. I heard the big 'crack', too. I checked the fork steerer and decided that the compression plug in the Ouzo Pro fork had slipped up just slightly and allowed the King HS to have just a slight bit more play than it should have had.

I tried to really tighten the compression plug and then reset the bearing preload. I had no more trouble.

The frame and fork are now back at Serotta for a repaint and some brazing work on the seat stays. I'm sure they'll check everything over. During my inspection of the fork, I could see no issues.

Mike in AR:beer:

[pdxmech13]

Forks are cheap. Hospital visits however are not. I've always found that if your skeptical about something there is probably a good reason.

[djg]

What Dave Kirk said . . . both because he knows lots more than I do and because it seems to me that he's hit the nail on the head: if you're nervous about your fork every time you get on the bike (you've pulled it twice now?), then maybe it's just not worth it, especially as there are good forks available for relatively small sums of money. I don't have any particular reservations about all carbon forks, but I'll mention that AlphaQ makes a road fork with an OX Platinum steel steer tube -- it's relatively inexpensive, it doesn't weigh a ton, and it's a pretty good fork IMO.

[RPS]

Anyone with experience with this kind of thing?If you are not going to have it inspected professionally anyway, there is another test you can do yourself beyond the obvious visual. I asked an expert once about a fork that appeared OK after a crash that destroyed the frame (I expect a more severe incident than what you describe here), and he said to “hold it by the steerer tube and strike it against your knee to try and get a tone out of the fork, like a tuning fork. If it sounds "dead" with no sustain, then the fork is not safe to ride.”

I tried it on a new carbon fork (except I used the palm of my hand instead of a knee to strike it) and got a nice tone out of it that remains for a few seconds (I’d guess about 3 to 5 seconds). I’m assuming that if the fork had internal cracks it would be more “likely” to sound dead (more like a thud), or for the vibration to die down much quicker.

This may not prove that it’s good, but may prove that it’s bad. ;)

[CNY rider]

Thanks everyone for the responses.

You've all made me feel much more comfortable about the fork yet there's still just something in my head that feels glad I bought a replacement.
I'm not even sure at this point which will end up on the Hors. Given the depth of the snow here I've got at least a couple of months to stew on it.

The Shimano Pro I bought has an alloy steerer and cost me a grand total of $90 shipped from bonktown. I have other frames with 1 inch head tubes so if I don't use it now I still won't mind having it on my parts shelf.

[David Kirk]

Might make a nice lamp!?

banana



dave