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Old 09-19-12, 11:09 PM   #1
RubeRad
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CF: is this frame cracked?

Hey gang, I need your advice. So I recently pounced on a deal as no-brainer for an easy flip, but upon closer inspection...

The bike is a 52cm Kestrel KM40 Airfoil, Dura-Ace 7700, with Spinergy Xaero 650C wheels (with those funky PBO "Spox"). It's been sitting in a garage for 10 years, packed in a shipping hardcase (I got the case too!), so it's probably from 2000 or so (S/N 43823 if anybody can help me nail it down). Here's the whole bike:


You can see there are a number of scuffs and scrapes on the paint (many crudely daubed with non-matching nail polish!), but when I was cleaning the frame, I discovered a potential crack (or I guess two potential cracks in close proximity) on the shoulder of the left seat-stay. Here's a close-up (sorry, I'm no photographer, the flash washed it out, it is easier to see by eyeball in natural light):


So I flexed the seatstays by the squeezing the rear dropouts together (but only a little bit -- if it is a crack, I didn't want to make it worse), but I couldn't detect any structural weakness (the whole rear triangle seemed solid). Before I started cleaning it up, I took it for a few rides around the neighborhood, and the frame rode like a dream under my 240lb.

So how can I determine the extent of the damage here? I need to know whether I can honestly claim this bike has only cosmetic damage, or if I need to try to make my money back parting it out, and the frame is just a writeoff?

Note it's not an option for me to keep it and ride it; I am not a triathlete (hell, I'm not really even a monathlete!) so I cannot make use of an aggressive TT bike. The original plan was to swipe the DA group to upgrade my roadie, and make a few bucks selling the frame, wheels and hardcase. But if the frame is worthless...

Last edited by RubeRad; 09-19-12 at 11:22 PM.
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Old 09-20-12, 08:51 AM   #2
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If you are in SD take it here and see what they say http://www.carbonframerepair.com
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Old 09-20-12, 09:02 AM   #3
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Hey cool, Escondido is a stone's throw from where I work -- thanks, I will bring it to them for a professional eyeball and quote.
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Old 09-20-12, 10:29 AM   #4
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What does it sound like if you tap it gently with a small piece of dull metal such as a wedding ring? You would be trying to hear a difference between the sound you hear of the area around the flaw and that of the flaw. Just a thought.
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Old 09-20-12, 10:49 AM   #5
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Tapping the surface could just be a long shot means of diagnosis for a CF frame like this at best. You might back it up with a visit to a a shop that is familiar with these Kestrels. These monocoque design CF frames are just a whole different ballgame compared to more conventional lugged or welded frames, so you need people that are used to dealing with this type of bike to look at it too for the best diagnosis.
Just note though, that if there is a crack there, that it is repairable by companies like "Calfee".
I suggest that you don't ride the bike till you get a better idea on what's going on, lest you further damage the frame (and possibly get into an accident too) if it is a crack.

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Old 09-20-12, 10:49 AM   #6
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Take the seat post out,pressurize the frame with air,use soapy water on crack area,look for bubbles.
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Old 09-20-12, 12:04 PM   #7
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Tapping the surface could just be a long shot means of diagnosis for a CF frame like this at best.
Not to be argumentative but since you regard the use of sound as a "long shot" , I wonder if you could expound on your views of using sound in medical diagnostics or oil exploration. Geez, how will I survive the day without you letting me know if I'm about to waste my time?

Your suggestion, is great if you're the owner of a bike shop or repair facility. Let's see, you walk in with the bike and ask, "Is this cracked and if so is it repairable?" I answer, "Yes" on both accounts. Has the OPer really gotten good advice from the "experts"? Or is he just getting advice that will "stimulate the economy "?

I hope the OPer won't be discouraged from making some assessments on his own.

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Old 09-20-12, 12:25 PM   #8
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Thx for the advice all; I will not be riding it now that I suspect a crack, and I will certainly try some light tapping with my wedding band, and maybe a wrench handle. It certainly can't hurt, and if it does sound different, then I have an answer; if it sounds the same, nothing lost.

As for pressurizing, I'm not sure how I could accomplish that. Sounds like something a carbon repair shop would be equipped to do easily. I wonder, if I took the seat post out, whether I would be able to peek down the hole with a flashlight? I'd guess that, even if I did have line of sight to the inside of the suspect area, I wouldn't be able to discern anything. Or what about scraping inside there with a coathanger or something, if it is a crack, might I be able to feel it?
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Old 09-20-12, 01:36 PM   #9
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Thx for the advice all; I will not be riding it now that I suspect a crack, and I will certainly try some light tapping with my wedding band, and maybe a wrench handle. It certainly can't hurt, and if it does sound different, then I have an answer; if it sounds the same, nothing lost.

As for pressurizing, I'm not sure how I could accomplish that. Sounds like something a carbon repair shop would be equipped to do easily. I wonder, if I took the seat post out, whether I would be able to peek down the hole with a flashlight? I'd guess that, even if I did have line of sight to the inside of the suspect area, I wouldn't be able to discern anything. Or what about scraping inside there with a coathanger or something, if it is a crack, might I be able to feel it?
Light won't go through the kind of crack that forms in a CF structure. Air, humidity etc, yes, and in fact humidity weakens CF frames that aren't adequately coated.
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Old 09-20-12, 03:48 PM   #10
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Well I didn't mean trying to see whether light shines through the crack, I just meant trying to visually inspect the inside surface of the frame. But I don't really think this would work.
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Old 09-20-12, 04:55 PM   #11
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Kestrel still exists...just walked by 'em here at Interbike. Why not contact them and send 'em a photo?

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Old 09-20-12, 06:17 PM   #12
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I already contacted them through their website to ask them what year the bike was from the S/N, and I got a message back from some corporate overlord that they can't help me as Kestrel is owned by somebody else and there is no info before a certain year. So I don't expect they'll give the time of day for a possible crack in a >10yo bike.
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Old 09-20-12, 08:54 PM   #13
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Guess you won't be buying any newer Kestrels from them in the future...

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Old 09-23-12, 02:24 PM   #14
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I'm not interested in fixing it; I'm interested in not losing money on an attempted flip
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Old 09-23-12, 08:41 PM   #15
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The only way to know is to peel the paint and looks the under surface itself. Many paints with time just crack and that could be it, but w/o looking whats under the paint is hard to know.
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