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Old 08-21-08, 04:09 PM   #1
bkpker
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Cracked seatstay on carbon frame.

I have a question about a seatstay on a Giant ocr frame. My LBS has the frame in question, only ridden for a few miles before it was hit by a car. The left seatstay appears to have a pretty bad crack in it about midway between the dropout and the seat tube. My question is, would this frame be worth purchasing and fixing and how difficult would it be to fix myself? I am aware of two fairly popular and highly recommended frame repair companies, but im trying to obtain a carbon frame on the cheap and $300 for a repair is out of the question. Thanks for any info!
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Old 08-21-08, 04:21 PM   #2
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Run Forest...........run.
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Old 08-21-08, 06:39 PM   #3
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Don't do it! There is no way for you to tell if any other part of the frame has been compromised as well. The Bike shop should not be selling a broken frame, it's a legal liability nightmare.
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Old 08-21-08, 06:41 PM   #4
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Yikes.
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Old 08-21-08, 07:00 PM   #5
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JUST SAY NO,,,jeez
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Old 08-21-08, 07:02 PM   #6
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Danger Will Robinson!

And everyone wonders why I ride steel or Ti.
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Old 08-21-08, 07:59 PM   #7
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You can't "fix" a carbon frame.

You need to understand that the glue only is there to hold the carbon together. It's the carbon itself that provides the strength. Once you bust too many fibers in any given area there is no way to restore the strength to that area with just glue or any other method short of wadding on an exterior "splint" of carbon and epoxy over the crack and extending well out in each direction and tapering back to the original sizes. And I can't think of many folks that would want to see a wart of this sort on a carbon race frame.

So while it is pretty to look at and I know you're drooling over the idea just walk away. Carbon frames are like Humpty Dumpty. Once they fall off that wall it's curtains......
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Old 08-22-08, 05:57 AM   #8
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A broken frame is a broken frame, a fixed broken frame is still a broken frame. Go surf eBay and get a used frame on the cheap.
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Old 08-22-08, 06:24 AM   #9
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No way. I can't believe that shop is selling the frame. Legal liability nightmare. Obviously if it were your bike and you broke the seatstay, you could relegate it to trainer duty but no way I would try to repair it and ride it out on the road
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Old 08-22-08, 08:27 AM   #10
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+1000 to all of the above warnings. Unless you are willing to send the frame to Craig Calfee or another EXPERT carbon frame repair shop (and pay the $$$, which you said your aren't) don't even consider trying to fix this frame.
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Old 08-22-08, 08:32 AM   #11
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If cheap, use as wall art. Used bike stuff, IMO, makes for good wall art, as long as it is good and shiny, or at least clean.
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Old 08-22-08, 08:56 AM   #12
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Do Not Buy Broken Carbon Frame!!!!!!!

I am shocked the LBS is trying to sell a cracked carbon frame. IMHO, this should put all of their advice into the 'suspect' files. This shows extremely bad judgement.

Wow. No no no no no. Do not buy. You can get a nice steel or decently lightweight aluminum frame for cheap.

The bike shop needs to saw the carbon frame in half and throw one half in the garbage before they change their mind.

Wow. Holy krap. Bad idea. Yikes.
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Old 08-22-08, 08:58 AM   #13
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A Haiku...

Fixing carbon frames
As a last resort only
I would not ride it.
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Old 08-22-08, 09:11 AM   #14
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fix it for your ex's birthday...............
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Old 08-22-08, 10:03 AM   #15
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Tro' da frame away, mon!
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Old 08-22-08, 04:58 PM   #16
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I'd fix it, but they would have to practically give it to me. Someone's insurance has probably already paid for it anyway. I mean, it's just a seat stay. I've seen bikes ridden for miles with a completely broken seat stay. Not a real critical part; not like a down tube for instance. I'd agree 1000% with every comment that's been made here if it was a down tube.
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Old 08-22-08, 06:08 PM   #17
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Quote:
Originally Posted by Crank57 View Post
I'd fix it, but they would have to practically give it to me. Someone's insurance has probably already paid for it anyway. I mean, it's just a seat stay. I've seen bikes ridden for miles with a completely broken seat stay. Not a real critical part; not like a down tube for instance. I'd agree 1000% with every comment that's been made here if it was a down tube.
??? I might ride a carbon frame with a broken seat stay for miles only to get home from the crash. Last time I looked at my bike the seat stay was one leg of a triangle that included the chain stays.

Just saying...
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Old 08-22-08, 06:25 PM   #18
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bun E.

thats really a cute bunny..
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Old 08-22-08, 07:29 PM   #19
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??? I might ride a carbon frame with a broken seat stay for miles only to get home from the crash. Last time I looked at my bike the seat stay was one leg of a triangle that included the chain stays.

Just saying...
Yes it is one leg of a triangle. And there is another one right beside it on the right side of the bike. There is some degeree of redundancy here; at least enough that there would not be a sudden catistrophic failure. Not like a carbon fork suddenly turning into carbon cloth when a wheel fell into a drain grate; which I have seen by the way. I didn't mean it would be perfect, or even as good as it was before the crash, but I wouldn't be afraid to ride it myself. I certainly would not try to fix one for someone else.
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Old 08-22-08, 11:24 PM   #20
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I'd be worried about other, non-obvious damage to the frame from the accident.
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Old 08-23-08, 03:02 PM   #21
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You can't "fix" a carbon frame. .....
Sure you can. It's like with everything else, you just need the skills and the supplies suited for the job.

Quote:
Originally Posted by BCRider View Post
Once you bust too many fibers in any given area there is no way to restore the strength to that area with just glue ......
Quite right.

Quote:
Originally Posted by BCRider View Post
..short of wadding on an exterior "splint" of carbon and epoxy over the crack and extending well out in each direction and tapering back to the original sizes.
Well, the taper would be pretty much optional for a part loaded in compression, and the thickness of the splint wouldn't have to be more than 1.0-1.5 mm. But otherwise it's a fairly accurate description of a decent method of repairing a CF frame.

Quote:
Originally Posted by BCRider View Post
And I can't think of many folks that would want to see a wart of this sort on a carbon race frame.......
But it takes all kinds, doesn't it? If that would be the condition that'd let me ride a frame way above my regular price range I wouldn't have any qualms about it.
Besides, at 1.something mm it wouldn't be much of a wart.

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Carbon frames are like Humpty Dumpty.
Not at all. The big issue with (nice) CF structures is that they are so weight optimized and thin walled that it's really hard to make a "seamless" repair. OTOH with the strength-to-weight ratio you can get even a rather crude repair won't carry much of a weight penalty. And for a strut loaded in compression crude will do just fine.

Still, I agree with the overall sentiment about the risk of hidden damage. If I knew more about the damage mechanics I wouldn't hesitate to do such a repair and ride it afterwards. But the way the OP tells it I'd probably be more hesitant.
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Old 08-23-08, 08:57 PM   #22
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Thanks for all the input!

First, let me clear some things up that may have been a little vague in my initial post.

The LBS isn't trying to sell the frame, its in the shop and i happened to notice it and enquired whether or not it was for sale, the shop owner said it wasn't because it was damaged. I looked at the damage and it didn't seem like it was catastrophic, in fact, it appeared to me that it was in a location that would be relatively easy to repair and the damage wasn't extreme. I then asked the shop owner if he had thought of repairing it, which he said he didn't. I then asked if he would consider selling it so i could try to fix it and he said he would think about it. I fully realise that there may be other damage to the frame, but with something like this you must accept the fact that its damaged goods, attempt to repair it to the best of your ability and make it as safe as possible, or make it art.

I was interested in the frame for two reasons: firstly, i would love to ride a carbon frame and i don't have a lot of extra money for these types of things, secondly i think it would be a great learning experience to lay up a little carbon fiber and it would be a good winter project.

From my understanding the impact with the car was a slow speed one, the car was accelerating from a stop sign and hit it, so probably under 5mph. Also, the LBS owner looked the frame over and didn't observe any other damaged areas and all the components of the bike were undamaged. The bike was ridden for a while after the accident until the owner noticed it get "soft" in the rear end, at which point he noticed the crack in the seatstay and de-commissioned the frame. Anyway, i hear all the warnings about it, and i realize that im more or less taking my life in my hands if i attempt to repair it, but i would love to hear if anyone has tried anything similar and how they fared. If i were to repair it, what type of carbon would i use, what type of epoxy?
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Old 08-23-08, 09:22 PM   #23
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Carbon is carbon. The key is to lay it up such that it binds and strengthens the area while adopting the passage of the forces involved from the broken parts. There's various cloth weaves available with different ratios of warp to weave and which you'll want to use depends on the type of damage.

The epoxy will make a difference. First off what you want comes in bottles and not in squeeze tubes. You're looking for laminating resin rather than repair glue. The difference being in the type of resin and any fillers that thicken it for the glue aspect versus the thin and soak in aspect that you want. Ideally you would be able to email the frame maker and find out which resin they used and get some. If they don't want to play ball for liability reasons then something like West Systems resin would be an excellent bet. But even then I'd do an adhesion test by lightly sanding an area near the damage and then mix up a small batch and put a bead of the glue in place on the sanded area. Let cure and then try to pick it off. If it doesn't come off without a heck of a battle then I'd say you're good. But if it snaps off like an old bit of gravy from the kitchen counter then I'd go looking for a different resin.

A good place to start your search is to take the frame around to any boat repair supply outlets in your area. If you're lucky like I was and find that the outfit has a guy that takes a keen intrest in the business he'll have all sorts of questions and answers and guide you in the selection of the correct resin. If he's just there to collect a wage and doesn't know much other than to buy what he has then I'd look elsewhere. If he says all resins are the same and suggest you just use a polyester resin because it's cheaper and he has it but doesn't carry any epoxy except JBWeld then excuse yourself and run away as though he's the devil incarnate.....
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