Carbon Bike Flaws - Sand Through 

And to think that it's so easy/cheap to put a carbon or glass veil as the outermost layer so it serves as a sacrificial/tell tale layer for the sanding operators to avoid them going in too deep. Proper manufacturers do not shy away from even puting a superlight layer of woven glass (sub 20gsm) to help even more. Not to even mention that placing these sacrificial layers help with the surface finish out of the mold in a high volume operation (so less sanding is required), as it allows to vacate bubbles within the laminate by letting the matrix flow in a more free way during curing. Cheers for showing this and explaining that's its not a feature but a sign of bad QC and "less than ideal" manufacturing.

Damage like this is prevented in part during layup. The EPS Inner moulding typically helps prevent wavy and bumpy surfaces still Sand-through happens. And on virtually every frame (to some degree). You’re most likely to see at the edges and major junctions. You may find that there wasn’t enough resin at the surface of the part in that local area. Another succinct and credible review, thank you.

What an eye opener! It would be funny if weren't so potentially catastrophic. Clear coated with intact, unsanded carbon...... for all to see. Close to ideal:) From what I've read: It is OK to clear coat carbon fiber. But, there must be UV filter in the clear coat. Otherwise, UV will breakdown composite resin. It is just amazing they would grind a steer tube like that. Frightening. Great video. Thanks Raoul

Educational as ever Raoul just found this in the back catalogue, re-visit your vids so many times. A simple thank you for keeping us all aware and safer for it. Cheers 😁

This makes me feel better about the material I’ve lost inside the chain stays on my cross bike due to mud and dirt. I figured the chain stay-bottom bracket junction must have tons of material. (Famous last words). Lol.

Shocking stuff Raoul - great job as always in exposing it - literally and metaphorically. If you look at the side of the BMC downtube at 11 mins - in between your two red lines, the marbling makes a distorted picture of Frankenstein - kind of appropriate I suppose!

Well pointed out. Thank you

Very interesting! My BMC timemachine frame shows exactly the same looks at the same spots: top tube, chainstays, downtube. I am riding it since 2015, but i did not put very much kilometers in it, maybe 10k. Until today it works fine, no issues. Fingers crossed 🤞😌 !

Good informative video thanks 😊

Less than ideal... I'll get my coat.

WOW cool marble pattern 😮

Hambini's Top Advice,: Just by a Time skylon in bare carbon and you don't get this problem

I’ve had/built several Time bikes and, I’ve have always been floored by their quality of construction. I hope to hell they survive as I’ve little confidence in any mainstream manufacturer of carbon frames.

I've had few years old Cube Reaction frame painted with clear coat. Whole frame looked like in this video. I also have Scott CR1, from I think 2009/2010, and whole frame is in beautiful carbon fiber cross patern, without any of this crazy, post sending marbles. I also have BMC Team Elite... and I have to say, that i'm very happy because it's fully painted frame and I don't have chance to see this poor quality production method of modern bikes... 😉

There are obviously no quality controls, who knows what is under those flashy paint jobs

Fun fact: Our main cycling publication here in Norway just ran a happy story about the Norwegian industry designer behind the BMC bikes. Wish there were engineers at the helm in the development of bloody any product that has a safety element to it....

I remember back in 2012 when i had a test bike Giant tcr adv sl, one with bare raw carbon no paint just decals n clear coat. And I have have to say that looked amazing with non of this sand through or funny looking defects... obviously they don't do it as good now and mask with paint it would seem?🤔

BMC has a three year frame warranty while most companies have a lifetime warranty ( track/specialized). Sharp edges and corners have always been a poor design for carbon yet BMC has promoted its angular/square edges as a good design. Even their seatposts have sharp corners that fail as well.

So many bikes have varying degrees of sand through. Like nearly all of them. My ROSE bike looked mostly like the BMCs in many places.

Hey Raoul, bring back the yellow marker..😁

I guess pretty much all carbon bikes have that to certain degree (except for Time), some underneath the paint, some exposed, do they? Should we really be worried?

Ugh. I like metal frames. But I still use a carbon fork. I wish all manufacturers had to run their carbon frames and forks through a scan analysis to discover any voids or flaws. Supposedly Canyon does this, but a lot probably depends on the quality of the scan and the analysis.

I've just finished hand sanding my Trek MADONE back to bare carbon. It took 30 hours in total, as I was super careful to not touch carbon (for >99 percent of the time anyway). The positive, is that there is almost zero sand-through across the entire frame, fork, seat posts and ISO Speed - just a couple of very small bits on some of the tighter radius corners - and a couple of 'very' small areas I unfortunately introduced.

Hi. You mentioned that silicon oil is particularly damaging to carbon fiber laminates. I assume that would apply to silicon grease also. Is there any grease or paste that is suitable?. I want to seal up the gap between plastic plugs that I 3D printed and the frame to prevent water ingress. Thanks!

I got tired of all the chips in my 2005 Roubaix paint so I decided to go clear. After too many hours of hand sanding, I grab my drill and disc and went to town. I have plenty of these aggressive sand areas all over the frame, some scary. My sandthrough looks less dangerous than some of the manufacturing bonding though. This was two years and some 6000+ miles ago and no problems.

A question. I've always assumed the outer mould would be close to perfect, and that the pressure would be close to perfectly pressing the material against it. If anything, I'd expect any deviation from perfect outside shape to be depressions rather than protrusions, and to require filling rather than sanding?

Thank you for bringing that to our attention. So what carbon bike can we truly trust anymore?

But is the frame lighter afterward 🤔

Any news yet on getting some road ridden SL7 forks from viewers in? Surely a quick video asking for them would get you plenty of offers. Seems it's all getting more about t-shirts. Less than ideal.

So the ideal here is uniformed carbon pattern. What if the sander is the one doing it wrong causing uneven looks hence looks delaminated.is that possible? But then I guess ideal here is adding more ply so even in areas of delamination, underneath is more support. If that is for repair you'll trim that then add another ply or total remove it?

Another example for a non-existing qc at the bling bike brands. 😂. Happy with my flawless noname bike with perfect layers under a thin clear coat.

So the 'marble' on naked Factor frames is sand through? Nice ...

Found some sand through inside the frame of my brand new domane sl5 gen4 where the frame storage is, under the bottom of the down tube. Looks like they sanded through a few plys of carbon my question is why are they sanding inside the frame? and should I send a picture to trek and file a warranty claim. Funny thing is it has a green check mark next to it which I'm assuming means it passed qc even though there's an obvious deffect in manufacturing.

I watched a carbon frame factory tour today. All the workers were sanding the frames, paper face masks covered in carbon at the nose. They were definitely Sanding into the carbon and breathing it

What about Campagnolo? This marble appearance is a feature with Campy cranks and in some components.

I would seriously hope the sanding is factored into the design, with the top N layers deemed dispensable?! Of course, there's no guarantee that the chaps in the factory won't sand away more... power sanders on a carbon frame FTW 😨

Your videos make me glad I chose aluminum. However the fork is carbon with aluminum steer tube and dropouts. The fork seems as stiff as the rest of this track bike, so maybe it's over built. I do look at the junction areas for cracks periodically. As a road bike, this one feels amazing on short sharp pitches!

Hey Raoul, considering all these sanding issues, what is your opinion on sand-blasting frames for paint removal? (in order to re-paint or in order to save weight) Any risk of removing structural material in that process?

So I have a question. I have two bikes.(road and gravel.) My both bikes are carbon fiber. They're both Chinese knockoffs of specialized. It was a lot cheaper but it was a reputable brand. The one brand was a very good knockoff brand but in their country. I guess it's name brand. When I sanded the road bike it it down it was a perfect weave pattern through the whole bike with a little things that I saw like in your video in the bike. But then the gravel bike was from a different Chinese knock-off brand and almost got lost and took 7 months to get here and when I sanded it, I don't hardly see any weaving pattern at all. When I sand it off the paint. Sometimes I do but most of the time I see very long kind of like that fork you showed the specialized fork or it's a long strip at a 45 and then the darker image going. Another direction I guess is what you said. But the whole bike is like that. And I don't see any weaving the 3D or 4D weaving anywhere. Hardly anywhere on the bike. Is that normal or is that can the bike be not woven like that and just have these long strips of carbon fiber? Is that sound right? Because now it's ugly it doesn't look. My other bike came out great. I sanded it down, polished it put a poly epoxy resin paint job over it. Clear coat and it just pops is other one is just looks like almost looks like metal because it's just looks like different shades of gray going. Which way and what? And all kinds of damage marks like in your video but is that normal or should it have a 3D pattern and I haven't stand it enough? Or did I somehow sanded it off? I doubt I sanded it off cuz I'm very very careful when I do that but it's just weird it looks it has all that marbling in it like you had talked about lots of marbling a lot of those strips of black and white lighter shades of carbon fiber but not it doesn't look pretty at all. Sand it down compared to my other one. I'm excited because now I have a road and gravel bike but I wanted to show off the carbon fiber because I'm not very rich and so seeing a whole carbon fiber bike frame carbon fiber rims carbon fiber seat handlebars everything carbon fiber. It's you know I love showing it off and pulling up next to the someone with their for $5,000 bike in mines. All Chinese knockoff of their stuff and it's good. There's good and bad Chinese knockoff brands out there but this one was a very good Chinese knockoff brand. I've did a lot of research at least for the road bike. The gravel bike was just a no name. It was like 200 bucks for it and I got it but seems sturdy. It's very light but yeah what is up with the bike?

Simply not acceptable...especially considering the price tag.

Would you advise against sanding off a pre painted frame to get it repainted?

I had a raw tifosi frame . That had zero of this marbled look . I could see the weave was uniformal, I could see on the fork the different directions of the weave but there was no sanding marks but I could see the joins in the carbon . It wasn't an expensive frame and obviously not to a high standard like time but it seems like they at least took some care in manufacturing.

Could it be that the sanding through happened when they removed the paint? Fork specialized

Why is silicone oil so bad? I tought silicone grease is pretty much compatible with everything? Of course ester or polyalkylene glycol based oils are incompatible with a lot of plastics and syntheic materials, but silicone?

I just don’t get it. How is carbon supposed to be so strong when used properly, yet so fragile when these things happen.

Perhaps show some examples where a sand through has resulted in a frame failure, as it stands this video doesn’t prove anything has been done poorly that could result in a flawed dangerous product 🤔

It seems most big name bikes have these flaws, and in practical terms they probably cant be altogether avoided. I wander if there are actually any well known brands that do produce frames largely devoid of such defects?

Raul...you are as dry as a desert,but i like your style!

"what is the result and the effect on the structural properties?" I can answer that... it's less than ideal.

4:05 why do I see animal muzzle on a carbon steerer?

Watches video. Checks 2017 Specialized Crux fork. Cries. 😭

Surely there is a single non structural lightweight lamination on the outside to allow for just this kind of thing and general wear and tear in general usage? Plus a factor of safety in the design assumptions?

In my experience they use a belt sander not a disc sander. Is that what you meant? Sorry about being so picky about the details. Nevertheless it doesn't really change the impact of your examples.

This is dangerous ladies snd gents. Whatever happened to nice soft wet sanding by hand ✋ with 3k, 6k or 10k paper?

Oh shit, my whole bike looks like that... Now I´m a little bit worried, using it since 2016.

I'm surprised this passes QA😱. It's so obvious, not even hidden within the tubes

Specialized recently had a series of bikes with just clear coat and decals only. You could see all the layers ... and nice marble art. (Just kidding ;)

But the frame is molded in that shape, they are not sanding the carbon down to achieve that shape. Don’t they typically do a light surface sanding to smoothen it out on all carbon frames? Most frames that are bare carbon come with a finish like that. But frames like Time with the 3k weave just have a “beauty” top layer of carbon to give it that look. I’m from the aerospace industry and have worked with carbon and for us to achieve that beautiful top layer like Time or Pagani Zonda it’s just a extra top layer of carbon. I could be wrong but that’s what I’m thinking.

Nice, but what's up with the clapping at the end? 😅

So what you're saying is we should only buy frames that are painted in opaque colours? Ignorance is bliss right?

What was the clap Raoul?

Sharp edges is the entire BMC design ethos. Alrighty then, no BMC carbon bikes for me!

Bike industry solution to this problem "let's paint the corners"

@13:35 My man has a brain cramp. Sorry, it happens to me too all the time.😉

that particular marble-pattern salesman dislike this video

This bmc is one of best looking bike ever. No problems at all.

Tell me again why CFRP is a good material to make bikes out of? Isn't CFRP supposed to be stronger and never fatigue?

Makes one to seriously consider going back to alu frame or even Ti. This I know can't ever happen. Like they said can't turn back the clock.

When the bankers got involved with cycling everything went to shite.

And that specialized fork is worse than cheapos I've purchased straight from China.

Wow that's bad. It's not cool marble material, it's badly-varied layers which you've then futzed back to smooth! I had no idea this was available on commercial bikes. You can do a better job at home wrapping tubes with doped cloth and compressing with cling wrap!

BMC most expensive bike always has the worst crap carbon frames...

I still don't trust carbon mtb handlebars. I trust the material, but not the quality control in mass manufacturing

This is too fast for playing it at 1.25x speed 😁

I don't like sand, it's coarse, rough and irritating...

Steel is real carbon💩💩💩

carbon, as a material, is less than ideal.