Monday, May 17

Damaged Carbon Bike

Snagged from "Cycling, London, and Life" - Ham's Fork. Hmm...
If you have damaged, or suspect you have damaged your bike frame, fork, or seat post, you have four choices. Regardless of your choice, I suggest you start by taking the damaged item to your local mechanic. While few local mechanics have training or equipment to effect a carbon repair, they MIGHT be able to help you get consideration from the manufacturer on a warranty action or manufacturer goodwill gesture. Yes, it may be a long shot, but an inquiry is always a good start. In rare cases, a local mechanic may know a place to go for composite repair. If nothing else, you’ll feel a better about whatever course you may take afterwards. I also suggest that you take GOOD, dated photos of the damage and the damaged area for future reference.

#1 – You can ignore the damage and hope for the best.
#2 – You can send it to a specialist.
#3 – You can proof load it to verify it is safe to keep in service.
#4 – You can scrap the thing.

Depending on the component, any of the four choices may be best.

IF the damaged item is unlikely to cause serious bodily harm upon failure, I suggest using approach #1, #3, or #4. Components I would take this approach with include seat posts, drivetrain components, and items such as the carbon water bottle holder. Actually, I’d ONLY take approach #4 once the offending part either broke or was clearly falling apart. Obviously, if your carbon water bottle holder snaps, it’s time for #4.

IF the damaged item is so expensive that #4 is unacceptable, and the damage is severe and readily apparent, I suggest considering approach #2. In truth, if you have enough money, almost any carbon damage CAN be repaired and made as good as new. If you are the sort who enthusiastically has learned how to build his/her OWN carbon bike, as outlined here, you can repair it yourself, and then apply approach #3. I would usually restrict this approach to structural damage to the frame itself.

IF the damaged item’s failure might inflict serious bodily harm, but isn’t the frame itself, I suggest you consider approach #3. The advantage of approach #3 is that if it fails in proof load, #4 becomes a “no brainer.” Items that fall into this category include the front fork, wheels (especially the front), and handlebars.

Notes on #2
Assuming you come up short locally, there ARE outfits that perform structural repairs on composites. One example is here. Another is here. They’re not cheap, but neither is a new carbon frame.

Notes on #3
This merits a separate post of its own. IMHO, this is the only reliable and economical way you can ensure that your damaged carbon bike item is safe. Keep in mind that if it FAILS, it WILL be broken. At that point, unless you have complete and thorough documentation of the actions you have taken, the manufacturer will probably take the position that you have voided any warranty by your actions. "Do ya feel lucky, punk? Well, do ya?"


cycler said...

#3 reminds me of the Calvin and Hobbes where Calvin asks his father how bridge load limits are determined. His father without missing a beat tells him that they drive heavier and heavier trucks across it until it fails.

The thing that concerns me, as an architect is how do you perform the loading test. A static loading test is relatively simple to perform, but it seems like dynamic loading is where you would see a high percentage of the failures (in bending, and bending plus shear), and it seems like that would be hard to replicate in testing.

Doohickie said...

#5: Put some clear nail polish on it and call it good.

;- )

Steve A said...

#5 is the same as #1

John Romeo Alpha said...

I definitely look forward to the post on #3.

Ham said...

Looking forward to (3), too. In this instance I will keep a careful watch. Unfortunately, I have relatively little faith in the average local mechanic. In this instance, I would be hard put to suggest that it was a manufacturing fault ;-). And, although it is only two years old, it looks like what it is - a bike that has covered about 8,000 London miles. (By my estimate, 1 London mile = 3 - 4 other miles)

Chuck Davis said...

On a tangential aside, last fall at a local CX race a rider dropped out with a CF seat post that had seemingly snapped off of at the top of seat tube, he told me that it wuz the third seat post he had break on (under?) him that season

There may or knot have been a "message" here!

Chuck Davis

Rantwick said...

Carry on, Carbon Man! I join the others in pondering what would be an acceptable proof loading of, say, a fork, since that's the only carbon item I possess. Are you really gonna post on that? I hope so. Science and engineering is awesome stuff. I really blew it when I took English in University. (sniff)


cafiend said...

Proof loading: drink some 40 proof. Go for a ride. Drink some 80 proof. Go for a ride. Repeat up to 151 or whatever you can get. At higher proof you will have more frequent and harder crashes. Obviously if the bike survives it's okay.

You might be another story.

Velouria said...

Once again, I shudder as I read about "potential bodily harm" - imagining things like forks snapping and amputating legs, or being impaled upon seatposts... Mr. Petersen has gotten t me pretty good : )

Steve A said...

Velouria, did I mention the 23lb step-through carbon bike? Imagine flying up and down steps with a bike such as that!

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