morfeeis

Just saw this video of a carbon wheel disintegrating upon contact with the road. Well this is a one-in-a-million situation I thought it was interesting given the more recent debates about disc brakes

rydabent

Just another example of the wonder material not being so wonderful at all. Again, they call them carbon fiber rims, but they are really plastic rims reinforced with carbon fiber.

It also reminds me of back in the 80s when the lightness craze struck, and every component was drilled out. Then they started breaking and racers learned that lightness was not good if you didnt even finish the race. Light "carbon fiber" rims probably feel great, but if you dont finish the race, they too are worthless.

FBinNY 

Sorry, but no. They are made of laminated sheet of woven (or non-woven) sheets of carbon fiber, laid up using a resin filler/bonding agent to hold them together. The construction is more like how fiberglass boats are built, than any molding process.

The failures aren't because of any inherent problem with the material, they're because of decisions taken by the designers, and/or quality control in the production process.

The simple truth is that these parts are failing because they're underbuilt, which could happen with anything, but we see it with CF because that's the material of choice for those looking to save weight.

coominya

Who cares what their made of, or how they were designed, they collapse catastrophically and that's all we need to be aware of. If someone wants to ride them knowing the risks that's their choice.

I have popped a few spokes on my aluminium rims over the years but have always ridden home, never had or heard of anyone having an aluminium wheel completely fail.

rgconner

Oh, they do completely fail.
On a ride with a mate, he hit a small pothole and the front Mavic rim failed, pulled apart like metal taffy.

WizardOfBoz

There's a book called "To Engineer is Human" by Henry Petroski, a Duke engineering professor. Talks about how engineering design evolves. You start with a bunch of people building stuff with different designs. Bridges, for example. Some fail, as some aspect of service duty (cars on the bridge) causes one or more stresses that exceed an aspect of the design. The designs that fail, you don't use again. The designs that succeed, you use for the next bridge. But the next set of bridges may be twice as long. So you may add in some new designs. The longer span exposes weaknesses that weren't apparent in the first (shorter) bridges. So some of the new bridges fail. As you keep making longer/higher bridges that must bear more and more weight, The designs evolve. The service duty addressed by the new designs become more demanding as well. As these things evolve, new weakness are exposed.

In racing bikes, where these guys would kill for 15 grams, the drive for lower weight can have consequences like this. So it may be that the design itself had hidden weaknesses exposed by the race. Or the manufacturing techniques which were good for thicker, heavier carbon fiber layups, is not adequate for the new lighter designs. Or, as others have observed, the mfr may have made a bad wheel.

Just saying: at the bleeding edge of racing, where you have ultra-light designs and riders with incredible leg strength, one would expect some failures like this. As rgconner points out, wheel failure is not confined to carbon fiber. One lesson that's probably useful here is that the wheels used by pros in (for example) the TdF are pretty much optimized for weight and not for longevity. The same wheel that's perfect for such racing, and where the pros view wheels as consumables and don't care if they need a new set of wheels every day, may not be a very good choice for those of us who ride 10-40 miles/day, or commute.

Juan Foote

Yup, have to agree. I have seen wheels come apart on both "10 speed" and "BMX" style bikes. Lol, one of the BMX ones was supposedly indestructible. Challenge accepted...

Trsnrtr

I've broken two aluminum rims over the last 35 years. It happens.

rydabent

"resin filler/bonding agent" = Plastic!

Seattle Forrest

Seriously? You've never heard of an alu wheel fail completely?

corrado33

Please excuse my ignorance, but aren't most CF parts built today using high pressure molds? Sure, it's still CF laid in layers with resin, but don't they use molds to get them into the right shape?

Here's a video on trek's CF bike frames. At 5:40 they talk about a "press used to push both halfs of the mold together."


But, as for the failure in the video. Meh. I see one of three things happening. One, the tubular tire fell off and the CF rim got eaten up by the road to failure or two, the tubular tire fell off and wedged between the wheel and fork causing catastrophic failure. (Although I would imagine damage to the fork would be apparent.) Or three, one of the 'spokes" of the CF rim failed and caused the rim to go out of "true" enough to hit the forks, eventually compounding into a failure.

EDIT: I watched the youtube video in slow motion. A few frames before the "failure" you can see a "hoop" of black seperate from the rim. I'm going to assume that's the tire.

Face it folks, CF has proved to be strong enough over the last many years. If the mountain bikers can use CF, you can use CF on your road bike and be just fine. With that said, since I'm not a racer and don't count grams on my bike, I'll stick with nice aluminum rims for the time being.

TimothyH

This shouldn't even be a point of conversation.

All bets are off when you ride a rim with no tire as happened in the video. This is especially true of racing components which are made as light as possible, often at the expense of durability.

The fact that any racing wheel failed when ridden with no tire does not surprise me in the slightest. It isn't a Ford F350.


-Tim-

WizardOfBoz

Also, to those who don't think CF is "strong enough" for bikes: you DO know that this stuff is used in airplanes, right? Like the F-35 fighter, which is about 35% by weight CF. If something like that, with 41,000 lbs of thrust, holds together even after absorbing shrapnel, I'm pretty sure that something that absorbs a couple of hundred pounds force will be adequately served by the same material.

corrado33

While I do like the comparison, I believe the load profiles for planes and bikes are different. Even though the new dreamliner is something ridiculous like 90% composites or something like that, the landing gear frame is still made from aluminum.

Bikes have to deal with sharp shocks all day every day when they're ridden. Planes well... sometimes do. But I'd imagine the force profiles for planes are much more smooth unless they're hitting a lot of turbulence. And the force on a plane is spread out over a lot larger area.

This is all speculation of course. I've never been in a fighter plane. Hopefully someone will come correct me.

jgwilliams

I've broken one as well but that was many years ago. Back then they were extruded in a sort of gutter shape (I imagine they still are), bent in a circle and fixed with a connecting piece. I was forced off the road one night on my way home and the rim broke where it was connected. That was probably around 1974.

I'm not sure how the two ends are joined now - they look as if they may be welded - but I'm very sure they are much stronger these days. My Ksyrium wheels have taken a couple of pretty good thumps without even going out of true. I'm also quite certain that my riding style doesn't put a fraction of the stress on wheels that a pro would.

AlmostTrick

"Forced off the road" sounds a lot less unpleasant than being forced down into the road. All failures are not equal regarding the warning they give, and the injury they inflict.


And while any material could fail, one or another has to fail more often than the others... it's not possible that all would fail at the same rate.

That may be, but I'm guessing you're also not swapping your wheels out for new ones several times a year either.

SkyDog75

They can be pinned, sleeved, or welded. Sun Ringle describes the methods on their web site HERE.

FBinNY 

I find the entire "CF" debate somewhat interesting. It's become a for or against emotional debate that tends to ignore reality. I post a response to someone who demonizes CF parts as being made of "plastic" as if that means anything. People seize on one sentence out of three, while ignoring the other two, where I blame the engineers.

Let's try to get past the pro or anti CF debate and look at what's going on, which is a high stakes race to produce ever lighter components, where makers take (mis)calculated risks in an effort to beat their competitors. This is comparable to high speed descents in racing, where a rider tries to take a curve at the highest possible speed, and gambles a relatively safe second or third place finish, in an effort to take first, unless he can't hold the curve.

As I said in my earlier post, the problem isn't that the wheel is CF, it's that it's under built, plain and simple. One doesn't have to under build with CF, but the material attracts those who would because it makes lighter stuff possible.

By analogy think about the history of bridges. For millennia they were reliably built of stone, and the Romans elevated stone bridge construction to amazing levels. But there was a limit to the spans possible with stone, and some 200 years ago engineers in pursuit of longer spans started using iron and steel. They used a variety of new and untested designs, and achieved great leaps in spanning ever wider rivers. However Steel bridges suffered spectacular failures, and I'm sure there wore folks who called them the Devil's work and that we should stay with tried and true stone construction. But that would mean that most of our modern cities near major rivers couldn't exist.

CF today is where steel was 200 years ago, and we're pretty early into the leaning curve. But the material isn't inherently bad, and the problem isn't CF or not CF, but how much we're willing to risk in the pursuit of saving those last few grams.

Those who categorically blame CF based on videos like this, forget that there are countless other CF wheels by other makers that aren't failing, though they may not be the lightest out there. Going back to the bridge analogy, the anti steel folks might not have mentioned all the stone bridges that failed when their mid-river supports washed away.

IMO the only takeaway from the failure of these wheels is that they were under built, which is about design rather than material. Of course, some would argue against this also, and prefer to blame potholes and bad luck, which opens a debate about just how far we're willing to go in out pursuit of weight savings.

jefnvk

Odd, alternate sources (sorry if it was covered in the vid, I prefer reading to a guy on a web cam talking) seem to indicate it happened to three of Sky's wheels, while BMC, using the same, had zero issues. TO me, that sounds more like poor QC than anything, especially as the wheel in question has been available since 2014 without catastrophic issues. Past that, I'd look more at an incorrect setup or hitting debris that BMC didn't, over the material of the wheel itself. As noted, it appears the tire may be off before the rim exploded.

That said, I agree with everyone else who is on the "racing application failures don't transfer to the real world applications" bandwagon. I once worked on a rally team who snapped the same drive axle twice the same weekend, doesn't mean I walk around thinking Subarus are horribly engineered. It means I think we were using lightweight race parts and abusing the heck out of them.

https://cyclingtips.com/2017/03/team...eno-adriatico/

Retoocs

The use of carbon fiber in airplanes is mostly in the skins and cowling that were .030" thick aluminum. High load parts are still made of 2024, 6-4 Ti, 17-4 stainless, or other exotic materials.

nycphotography

fify.

nycphotography

Incorrect.

epoxy <> plastic.

(cf resin is more like epoxy than plastic)

merlinextraligh

It sounds like hitting potholes caused the wheels to fail. If hitting a run of the mill pothole causes 3 wheels to fail, then I'd say the wheels are either underbuilt, or there was a manufacturing defect in that particular batch.

Not an indictment of the material itself.

That said, these guys are racing, and these are race wheels specifically designed for TT's, so aerodynamics, and to a lesser extent weight are more important design criteria than durability. you could obviously design a bicycle wheel to be pretty much indestructible, but it would be slower.

WizardOfBoz

I agree that certain high load parts are still (for now) made of machined or forged metals. But 50% of the Boeing 787 structure is composite, and 53% of the A350AXB is composite. And I suspect that the stress on a 0.030" thick skin on a plane going 1200 mph (Mach 1.6!) is going to be higher than the stress my Domane's seat tube sees, even though I'm 240lbs.

gecho

Couldn't have just picked a version of the video that just shows the failure instead of a guy staring at his computer monitor for the first 2 minutes?