Help…Carbon frame cracks…paint or carbon?

Hi guys,

Received a frame yesterday and on inspection today found a series of thin cracks around the top tube/seat tube joint (integrated seat tube). This is my first carbon frame so not sure what to think. The seller didn’t mention in the advert so my gut reation is that it’s cosmetic but I want to check. Tubes all look straight with no waves or anything. You can just feel the cracks with a fingernail. Could it be just a bad paint finish and the flex of the carbon? What should I do?

Thanks

Hmmm, it’s probably just the paint from some very slight flexing, but needs to be NDT’d (non distructive testing) really.
There’s a carbon frame repair specialist up Silverstone way, can’t remember the name, but some one else might?, would be worth talking to them, as they may have the facility to test it too?

You can replicate a basic NDT test yourself. Get a coin and gently tap around and on the area you’re worried about. Listen for significant changes in sound. ‘Dullness’ can often indicate delamination etc. Having said that, you’ll get changes due to tube butting and joining anyway.

TBH that looks like paint to me rather than carbon. (That judgement based on 5 years working in the aero and motorsport carbon fibre industry rather than just being some sort of forum expert 🙂 )

Ok. Coin tap test doesn’t provide any significant changes in sound. The spots i’m concerned about sound like the rest of the tube. Would an x-ray show me anything? (might have access to one).

My gut reation was it was paint but i’m a novice with carbon so wanted to ask the experts.

Any other thoughts or words of wisdom?

Thanks

It looks very much like paint cracking to me; I have similar stuff on the dropouts of my road bike.

The paint doesn’t flex, or doesn’t deal with flex, as well as the carbon so it cracks over time. I’d be happy to ride it.

Assuming your seat post is in deep enough to be effectively overlapping that area, i wouldn’t worry. Any failure is unlikely to be catastrophic in that case as the seat post will be inside.

Assuming your seat post is in deep enough to be effectively overlapping that area, i wouldn’t worry. Any failure is unlikely to be catastrophic in that case as the seat post will be inside.

It doesn’t have a seat post; that’s the whole point.

Like this;

ISPs can have a lot of fore and aft flex. It looks like small cracks in the paint due to flexing and I wouldn’t be worried. I’d be a little disappointed, but it is the colour that is showing the crack. My ISP frame is black and I haven’t looked that closely.

Ah, i see, well, if it snaps off then it’s gonna be painful! 😉

Still bad form by the seller not to mention it IMHO. I would pay less for a frame in that condition.

An X-ray should show any cracks, but delamination between layers could be a bit more tricky, a CT scan would give you a 3d view of the joint.

Hmmm…still unsure then!

Probably just paint but a failure might be rather unpleasant.

Anyone had any experience of Non Descructive Testing? Guessing it’s not cheap.
Ride it as is?
Would removing paint to see carbon do any good?
Chop off the IST and fit collar and standard seatpost to reinforce?
Rush it to A&E and see if NHS will CT scan it?

I do indirectly, a company I worked for some years ago worked with a company who did it, but only on their own products.
I used to have fairly easy access to X-ray and CT machines, but not these days unfortunately or I’d offer to help, all ours are in secure areas now!

How easy would it be to chop the post and use a standard seat post and collar?

How easy would it be to chop the post and use a standard seat post and collar?

Trouble is you don’t know for sure that the internal profile is a standard size for a seatpost …

ahhh bugger that could be an issue!

I’d be ignoring the X-ray, CT scan, MRI stuff up there and either rub the paint off if you need to or just ride it as is.

If the frame was black, you’d never even see it.

What is the frame?

The frame is a Fluid XC29R. Fluid cycles were/are Milton Keynes way.

Give them a ring, show them the pics and ask if they have seen similar on their race bikes. Given that the frames come in white and green, I bet they see this after a seasons use.

Surely the the fact that there are loads of cracks, rather than just one indicates its the paint flexing rather than the carbon, which wouldn’t crack like that (the caveat being I have absolutely no qualifications to back that up)

Why not send the pic to the frame builder. I’m pretty sure they would tell you if thats something they’ve seen before, and if its a cause for concern

edit…beaten to it by crikey

The sheer number of “cracks” you have there suggests very strongly that it’s just a paint issue. Extremely, extremely unlikely for the carbon to crack in multiple lines like that, as once you get one crack that becomes the weak point. I’d happily ride that.

No qualifications here, but I’ve broken and repaired plenty of composite stuff and know how it fails.

What is the frame btw?

What is the frame btw?

Look 4 posts up…