woodcraft

fify

79pmooney

The one inherent challenge of using CF on bicycle frames (vs airplane structure for example) is the bike frames are 1) completely exposed to incidental damage from falling over, having tools dropped on them, bike racks and lock and car roof racks and are used by riders who may well not be careful about such hazards and 2) bicycles crash. The idea that laying the bike down on a turn, losing a lot of skin, perhaps sliding hard into the curb but getting up and riding your skinned butt home may well be a $1000 frame ending event when there is nothing to be seen on the bike; well that idea is often just plain lost in either ignorance or denial.

This is where older small diameter steel frames shine. That damage is very unlikely to be hidden. If the steel is compromised, there will almost always be paint issues, bulged tubing or visible bends. Denial carries a lot less weight when you can see the evidence every time you take out the bike.

Ben

andr0id

I can't agree more. I was an F/A-18 mechanic in the Navy and since it had a lot of CF components, we had classes covering CF basics.

CF is extremely strong in the directions it is designed to be strong in. However, dings and scratches can compromise that strength very easily. The most common failures are due to scratches and gouges or delamination from being struck.

Scratches cause stress risers just like with metal that lead to a crack under load. It is fairly easy to inspect for scratches and gouges.

Delamination is harder to find since it is often not visible. If you suspect an area is damaged, you can do a tap test with a nickle. Very light tapping on CF should also be a click, not thunk or dead sound. If it sound dead, get it inspected by a dealer or somebody in the know.

My somewhat educated guess is that most "sudden" CF failures that occur "just riding along" were previously compromised areas.

I still see a lot of people toss CF frames on hang and bang racks at big rides. Probably the heavier entry level bikes are built for this, but the more expensive race frames are going to be expected to be transported on roof racks or tailgate racks that don't contact the frame.

My Waterford has an Ouzo Pro fork, a CF seatpost and handlebars and whatever Dura Ace 9000 parts are CF. I also still ride a Cervelo P2C. I'm perfectly comfortable riding CF parts that are not damaged.

NYMXer

When I was shopping for a new bike, my local bike shop asked me if I intended on transporting the bike on a bike rack (he saw it on my car). When I answered "yes" he said "do not buy a CF bike" as the bouncing weight on just 2 points of the top tube was not incorporated into the design of the frame and he recommended either an aluminum bike or another bike rack. To this day, I'm certain he believed what he was telling me but I am not so sure that he was correct. I am also not sure he was wrong..... has anyone else ever heard that comment?

turkey9186

This exactly. Ten years ago it cost $35/gram once a bike hit 18#s to take off anymore weight. 99% of the serious cycling population could ride another 50 miles a week and lose that each week without too much problem.
A friend was recently stressing over buying a pair of $250 pedals to save 25 grams over what she had....on a 16.5 pound bike!
Boats, planes, and bikes are the same. You can chose two of the three....cheap, lightweight, or reliable.
As for carbon design, they are building sailboat masts and aircraft wing spars out of CF. Way greater loading than any bike will ever see pound for pound.

FBinNY 

There is so much mythology and mythinformation surrounding CF frames that's impossible for the average person know who or what to believe.

Unless one were to slam the frame onto the rack with a vengeance, the stress of riding on a rack is nothing compared to the normal stress incurred riding. This might not be so if the rack were attached to a paint mixer, but consider that the rack is on one ton plus vehicle suspended on springs. That means that the total g-force that can be transmitted to the rack or frame is very limited.

If you can take it as the driver or passenger, the frame can take it.

rydabent

Remember when the weight weenies had people drilling holes in everything in the 80s. They drilled everything, pedals and RDs included. But then most everything they drilled failed. You can be fast for a while with a drilled RD, but when it breaks, you dont win the race. You dont win races when your frame shatters either.

migrantwing

This is an interesting 30 minute video. The guy that is interviewed is an former Boeing aircraft engineer. An cyclist himself, he now does frame repairs and also builds bikes, components and shoes from Carbon Fibre.

He is very animated and very informative, fun to watch but also answers a lot of questions and gives in depth knowledge of all things Carbon Fibre. The guy is obviously very passionate and also knows his stuff.

Watch it and see what you can learn. Starts at around the 1 min 15 secs mark.

joejack951

TDF 2016: 174 finishers all on carbon fiber frame for 3500 kms/2170 miles (not counting rest days). That's a collective 609,000 km/377,580 miles of racing on carbon fiber bicycles. Exactly how many JRA frame failures occurred?

joejack951

Right. If you've ever sat on your top tube at a traffic light, you've done worse to it than carrying your bike on a trunk rack. I've done both many times without issue.

NYMXer

I don't think that's a fair comparison FBinNY because when you sit in a car, you are in the middle of the car on a suspended seat. The bike is at the rear of the car on a solid 2 point rack. Any bouncing (maybe not as violent as a paint mixer) is multiplied because it's at the rear of the car (think back seat of a school bus) and that bouncing force is applied to two specific points could lead to failure, IDK. It made sense to me but I still thought it was a bit exaggerated and wanted to see if anyone else heard similar concerns.

deapee

He was right.

Sitting on your top tube is a stress that's applied and exerted fully and isn't changing. Strapping your 19 pound bike by the top tube and hitting bump after bump after bump on a 50-mile drive day in and day out -- adds up to A LOT more stress than sitting on your top tube and then getting off it when you're ready to move again.

FBinNY 

Like many you're confusing force with movement. Yes the bicycle gets a "rough ride" but as long as it's securely strapped to the rack, it's tied to the inertial considerations that apply to the car. This is why and how seat belts keep you safe.

Going back to your school bus, the kids in back do get plenty of movement, but their brains don't get addled nor do their asses get bruised.

The same logic is why pilots want passengers to wear the seat belts at all times. In rough turbulence, the belts ensure that they move with the plane. They get shaken and spill their drinks, but they don't get hurt, unlike those who aren't strapped in and get bounced against other stuff.

Meanwhile, as far as I'm concerned, we've moved afar from the original question, and I think we're starting in circles, so having cleared up the rack question (I hope) I'll call it quits on this thread.

rydabent

Also all of them were probably brand new, or frames that had very few miles on them!!!

woodcraft

Drilling components happened long before, and also after the '80s.

Merckx did a lot to popularize the technique in the '60s, and won plenty on drilled-out bikes.

While plenty of parts failed as the limits were explored,

The style was mainly overtaken by focus on aerodynamics.

memebag

The collective distance doesn't matter. If I had 174 carbon frame bikes I might care how far 174 carbon frame bikes could travel.

Also, each rider uses multiple bikes, so each bike was used less than 2,170 miles.

And I don't think anyone outside the teams knows how many frames failed, so we can't draw any conclusions about mean distance between failures.

I just replaced my banged up, scratched, reliable aluminum frame road bike. I looked at carbon fiber and aluminum replacements. If I had a whole bunch of money to spend on replacement frames, I might have bought a carbon fiber frame. I don't, though, and the weight and road vibration differences weren't noticeable during my test rides. So I bought another aluminum frame. It may not be any more robust than the carbon fiber equivalent, but I won't be as worried about dropping it.

woodcraft

Destructive testing at Santa Cruz bikes- especially the 'whack the frame onto edge of concrete' test at end of video. (mtn bikes, but still...)

Santa Cruz Bicycles - Test Lab - Pinkbike


Fatigue testing of 12 lightweight frames. Trek OCLV was one of three that survived 20,000 cycles without failure.

None of steel or titanium did.

12 High-End Frames in the EFBe Fatigue Test

FBinNY 

You can't fight mythology with facts. People will believe what they want to believe, as they do on other fronts and have since the dawn of communication.

It doesn't matter how many CF frames are out there, how long they've been there, or how hard ridden without any issues, there will always be that photo, video or story of a CF frame failure (because EVERYTHING fails). There are also videos of steel, Ti and aluminum frame failures, but nobody cares about those.

A key issue on a bike is confidence or mental comfort. If you don't or feel you can't trust a CF frame, then don't buy one. But please don't try to rob others of their comfort level based on rumor or innuendo.

Jarrett2

That's a good point. But also, there are some facts out there about CF that many haven't heard. Or that like to be swept under the rug. Seems like providing this info is not the same as robbing others of comfort based on rumor or innuendo.

I'm not sure how many have seen that Specialized blurb that I posted earlier. Or know that they can crush their frame if they don't use a torque wrench on it. Or that a small tip over onto a sharp rock could compromise the integrity of the frame.

American Euchre

What qualifications lead you to declare yourself more knowledgeable than the "average person" on bike forums when it comes to carbon fiber technology?

Anyone can post a youtube video or an article on fatigue cycles they found doing a search on google.

American Euchre

The most qualified (probably the only qualified) guy in the room is android. He's taken coursework on CF. He notes that scratches/gouges and delimitation from direct impacts to the frame are responsible for eventual failure.

This is very different from the 'testing' that pink bike is engaging in here.


I've watched a bit of the migrant wing posted video. The speaker says the way CF frames are designed, they are designed to be so stiff that when they fail, they don't bend, they just snap. This is not very reassuring.

mapeiboy

Ok guys help me out here . I have a Colnago EP frame with carbon components on it that is over 5 years old . Since majority of people think the carbon frame is only good for one or two years max , should I trash this bike and get a new carbon frame .

American Euchre

So you're saying a broken seat post, broken chain stay, broken top tube, broken down tube, broken seat tube, broken handle bar, broken stem, broken saddle rails don't have serious consequences? Any of those failures can lead to 'serious consequences' for the rider. All of those parts are no less 'critical' for rider safety.

FBinNY 

Gee, 3 attack posts in rapid succession. Did you sit on a tack?

In any case, what makes you believe I'm any less qualified than anyone else? You don't know a thing about me or my credentials. If asked, I provide them to those who pay for my opinions, but for BF I let the body of my posts here speak for itself.

NYMXer

I would slowly and carefully check the frame over, while looking for cracks in the paint and materials. If it looks good to you but you still have worries, take it to you LBS and let them look at the entire bike. Share your concerns with them and see what they find, if anything. Then listen to them for any further instructions.