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Discussion Starter · #1 ·
Unfortunatly and before anyone asks, I got no picture to show but I'll do my best to describe the "crack" as good as I can.

I have a Kuota Ksano that I bought 1½ months ago. Rode over 1000 kms up to now and I really love the bike. Yesterday it was rainy and I decided to go for a spin anyways since it had been raining on and off all day long and I was sure it would stop. It did but the pavement was still wet and after the first ride's climb I started to take some speed. At about 17km/h I think I rolled over a rock or maybe the road was just bumpy, I have no clue what happened really, but my rear wheel washed out and I fell over. The impact was mostly absorbed by my hip and shoulder. The frame had no direct impact. The only visual damage to the bike is on the pedals, shifters and handlebar. Small scratches, nothing serious. I kept on with my ride for over 1½ hours everything still works great on the bike. When I came back home I reinspected the frame for signs of damage and noticed a thin hair-wide crack around 2-3 inches long on the down-tube, close to but not touching the bottle holder inserts. I cannot feel anything when rubbing my hands or nails above the crack's area so it is not a cosmetic damage. It seems as though the bond in that area cracked. Is that even possible? The best thing I can think of to compare it to is probably a scratch on the lens of a pair of glasses. It's very thin, white and I can only see it from an angle which makes me think it is a crack. What do you guys think?
 

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Sorry about your bad luck. :( Crack could be very serious. Kuota uses technology to create thinwall tubes that are all different sizes and shapes but create a totally bonzo frameset. I have Kredo and it's great.

Try to push on the material around the crack and see if there is any give. If it gives at the cracked area, you are *!#ked. It is possible that you could bond the cracked area with the right kind of adhesive, but I don't know what that is. It seems that you wouldn't crack a frame in that location unless something hit that spot specifically, so either the crack was there and you missed it or it might be a scratch. A pic would help a ton, I would get my LBS to look at it if you trust them, or talk w/Kuota, they can be very helpful.
 

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Discussion Starter · #3 ·
Donegal said:
t seems that you wouldn't crack a frame in that location unless something hit that spot specifically, so either the crack was there and you missed it or it might be a scratch. A pic would help a ton, I would get my LBS to look at it if you trust them, or talk w/Kuota, they can be very helpful.
It's exactly what I thought. It's a really weird place for a crack to appear but a defect can appear anywhere after all. Last spring I spotted a stress crack on one the side of my MTB's head tube. Being an AL frame it's a very uncommon place for the frame to crack and of course it was warrantied.

Anyways I tried to push the portion of the frame where the crack is in every direction and it's as stiff as ever. I really doubt it's a problem but I wonder if they'll want to send the frame to Kuota anyways, therefore making me race my next tri on my hardtail MTB...

As I said it's pretty improbable that it's a scratch as I would feel it with my nail but it could be. I'll probably drop by the shop tomorrow and ask them what they think.
 

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Do a tap test with a coin. If the area on the crack and around it sounds different from the rest of the downtube, then you probably got fiber separation. Sometimes even a coin tap test cannot tell if there is a crack. It's mainly good to check if any of the carbon fiber layers have delamination. Next thing I recommend is take a good, very defined picture of the crack next to a detailed ruler. Place one end of the ruler to the beginning or end of a crack. Go back to the picture after couple rides and see if the crack has propagated.
 

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Discussion Starter · #5 ·
tjjm36m3 said:
Do a tap test with a coin. If the area on the crack and around it sounds different from the rest of the downtube, then you probably got fiber separation. Sometimes even a coin tap test cannot tell if there is a crack. It's mainly good to check if any of the carbon fiber layers have delamination. Next thing I recommend is take a good, very defined picture of the crack next to a detailed ruler. Place one end of the ruler to the beginning or end of a crack. Go back to the picture after couple rides and see if the crack has propagated.
To be honest, I doubt this test has any significance since the down-tube of the ksano is neither round nor regular, therefore changing the sound produced with the coin. But to answer the test, the sound does change but it also changes all the way around the down tube because of the shape : https://www.kuota.com.au/images/frames/supersized/ksano_part2.jpg Even though this picture is the top tube, the down tube as a similar shape, it gets thinner but "higher". It kinda looks like it has a belly...
 

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Yeah, but all CF bikes are at risk for cracking. Someone just posted on a Cevelo with a cracked stay, and there was a post not long ago on a cracked Orbea. All of them are at risk whether some want to believe it or not.
 

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kcdoc said:
Yeah, but all CF bikes are at risk for cracking. Someone just posted on a Cevelo with a cracked stay, and there was a post not long ago on a cracked Orbea. All of them are at risk whether some want to believe it or not.

Horse Sh!T. Of course ALL frames are at risk of failing if the loads are great enough.

However, CF is not the brittle, crack and the drop of hat material that you seem to be implying.

There is currently no real indication that the Cervelo you refer to even cracked. While a cracked frame may very well sound different when tapped on, it is by no means a valid test.

In the case of the OP, the area is adjacent to the water bottle cage. That alone could cause significant sound changes.

If the "crack" has no depth to it, or if there is no movement, than it most likely is not a "Crack" of any concern.
 

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We dont disagree on this.. ALL frame materials and bikes (from all manufacturers) are at some degree of damage risk if the loads are great enough. I never even suggested that CF is brittle (not sure where you got that idea ). But to pinpoint Kuota as being a problem manufacturer is bogus and short sighted. As you state, the problem the OP alludes to may not even be a crack. So for someone to suggest 'here we go again, another Kuota problem' is riduculous at best.
 

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kcdoc said:
We dont disagree on this.. ALL frame materials and bikes (from all manufacturers) are at some degree of damage risk if the loads are great enough. I never even suggested that CF is brittle (not sure where you got that idea ). But to pinpoint Kuota as being a problem manufacturer is bogus and short sighted. As you state, the problem the OP alludes to may not even be a crack. So for someone to suggest 'here we go again, another Kuota problem' is riduculous at best.

If I misunderstood you, than I apologize for the tone of my post.

For some reason the CF paranoia drives me crazy. It is not a miracle material as some people suggest and I would choose steel, Stiff Ti or a multi material frame over a CF frame.

But the Sh!t is tough.
 

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No apologies needed. It is all in good sport in my mind. I ride both a lugged steel frame and a CF. I love both, and accept the good and the bad with both.
Its all good! If only i got to ride as much as i want
 
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