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Old 03-16-14, 03:03 PM   #1
tstansbury
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What's happening to this carbon Wound Up fork?

Our Wound Up Tandem Duo fork is showing discoloration/spotting where the brakes attach to the fork. The clear coat is clean and feels mostly smooth to the touch, except right at the metal/carbon junction. The fork is designed for both disc and linear pull brakes, although to date we have used only the linear pull. The problem areas are next to both brakes. The rest of the fork looks clear. The fork is two years old, with roughly 7,000-8,000 miles. Bike frame is ti. Team is 310 pounds.

Our retailer (Mel at Tandems East) is to talk to the manufacturer. Also, a local carbon repair guru will have a look at it. In the meantime, we're curious if anyone has had a similar experience or has a theory about what's happening. If this is merely cosmetic, we don't care much. If it's potentially more than cosmetic, then obviously we care a ton.

Appreciate your thoughts. Cheers all!

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File Type: jpg disc.jpg (86.8 KB, 49 views)
File Type: jpg closeup2.jpg (88.4 KB, 60 views)
File Type: jpg IMG_2214.jpg (89.7 KB, 64 views)
File Type: jpg closeup1.jpg (88.1 KB, 63 views)
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Old 03-16-14, 03:22 PM   #2
waynesulak
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I noticed on the only picture that shows below that attachment that it appears that the problem is above but not below the metal. It this the case at all locations?
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Old 03-16-14, 04:17 PM   #3
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Quote:
Originally Posted by waynesulak View Post
I noticed on the only picture that shows below that attachment that it appears that the problem is above but not below the metal. It this the case at all locations?
Hmm, there should be links to four pics. As for your question, the bike's in the shop now, but if I recall correctly, the affected areas appear above the metal in all cases.
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Old 03-16-14, 04:35 PM   #4
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I have a very similar '03 WU fork. It's seen a lot of use and bad weather, and is fine. When I look very closely at the top of the junction between carbon and aluminum on my fork, I see that the junction is filled to the top with some shiny material, probably epoxy resin. This is typical of such attachments and is called hardware bonding.

In your photographs, it looks like there is a gap between carbon and aluminum that was not resin filled and some substance is bubbling out of that gap. It is possible to get galvanic corrosion between carbon and aluminum because they are dissimilar metals, far away from each other in electrical potential. For this to happen, they have to touch each other. Well designed and built parts will have the aluminum and carbon insulated from each other with epoxy. However, it is possible that somewhere under the aluminum, it is in contact with the carbon and that what you are seeing are corrosion products of the aluminum because water and other electrolytes are getting into this gap. In these cases, the carbon is not damaged, but the aluminum goes away until it crumbles. I have had this happen on a carbon bike.

In your case, it seems probable that, if this is corrosion, it is limited to a small area at the top of the brake holder and is not too much of a worry. However, if I'm correct, WU should do something for you toward a new fork. This is not supposed to happen.
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Old 03-16-14, 05:59 PM   #5
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I am most certainly not qualified to diagnose your issue here but it looks like a bit of galvanic corrosion is messing with your clear coat.
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Old 03-21-14, 04:17 PM   #6
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Quick update... No formal response back from Wound Up yet, but a local carbon specialist looked at the folk. He thinks the discoloration is likely due to oxidization occuring under the clear coat, and that the carbon fiber is fine. Gold star in the margin to CFB for being the first to identify the culprit. While this doesn't seem like something that should happen to a high-end component, at least the initial report on the fork's integrity is reassuring.

Now, if somebody would please do something to stop the snowshowers and 20-degree temps we're being threatened with in a couple of days. Yeef, enough already, it's supposed to be spring.
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Old 03-23-14, 06:09 AM   #7
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I would have guessed the same action. The question is why is there oxidation occurring? Somehow, water or air is getting into a sealed joint or through a protective cover. It should be addressed.
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Old 03-23-14, 05:12 PM   #8
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I would have a difficult time with that evaluation. All my experience with these corrosion issues always see the corrosion stem outward from the aluminum. Your photo has speckles of clear coat "concerns".

The likelihood that you see corrosion on top of carbon, where it blisters the clear seems very remote. If there is visible corrosion on the aluminum adhesive bonded items, then you have a serious problem.

Often, to insulate the aluminum from the carbon, a scrim cloth of fiberglass is placed between the dissimilar materials.

I am probably wrong, but my opinion is the fork flexing has caused small disbonds to the clear coat. We have a similar version of a WU fork, it does move around a bit.

PK
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Old 03-24-14, 06:07 AM   #9
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Definitely speak to WU. This should not happen and you/we have no idea how it might progress. It's in WU's interests to know about this and if needs be replace. Good luck. They replaced for me recently even though over warranty (different problem - fine cracks - see earlier post).
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