We’ll let the arm chair engineers explain why this steel versus carbon failure test isn’t valid for cycling applications. Everyone else, please enjoy the science experiment.

Via Sploid


  1. This is stupid because when was the last time you saw a frame fail from torsional stresses, and when was the last time you saw a frame fail due to loads applied where the frame was meant to take stress.

    And Let me know when you get 8000nm legs.

    Otherwise crashes which kill frames don’t place loads where the frame is designed to take loads, and they don’t do it in torsion. Frame damage happens when forces are applied to a frame in a manner and in excess of what it was designed to take. It doesn’t matter what the material is.

  2. I would much rather be on a steel bike when it failed than a carbon or aluminum bike. When steel fails it bends which is much easier to deal with than sheering off or shattering. I am not a racer so a couple extra pounds don’t matter to me. Just my thoughts.

  3. Its a fun video, but it doesn’t answer the question in your post title does it? Nor does it really tell us anything we didn’t already know.

    Actually in the real world, a typical CF layup has a lower UTS than a typical steel used for a bike frame. But obviously the CF is a hell of a lot lower density so we use more. In the same way that Lotus are using more here and at a larger radius. Also in this particular case you can see that the steel (the grade of which isnt specified) is a lot more forgiving and winds up almost a full turn before failure, whereas the CF fails at just 20degrees or so, which means it may actually take less ENERGY to break than the steel (they dont actually show us the graphs to work it out)…

  4. One should also consider the distribution of crashes which fall into three categories. Crashes that cause no damage. Crashes that cause damage to one but not the other. Crashes that damage both. If the stronger material doesn’t meaningfully add to the category causes damage to one but not the other, then the difference in stregth is equally inconsequential. If the distribution was 48-2-48 it would not be much stronger in practice. If it were 48-27-25 then it would be.

    I don’t think anyone is going to argue steel can compete with carbon in strength to weight ratio

  5. I agree that this test isn’t perfect, but it certainly does show the strength / stiffness to weight ratio which carbon has going for it. The following video ( http://www.pinkbike.com/video/243228/) did wonders to improve my view of carbon strength vs aluminum. That being said, a lateral impact to any of the carbon tubes (from going OTB etc) could seriously compromise them…until we think of a way to protect the structural carbon from these types of impacts it will be sketchy for the user who demands years of faithful service from their frame….like me.

  6. There is no doubt carbon can be made lighter and stronger. If it couldn’t F1 cars wouldn’t be made out of it.

    But I have no interest in carbon until someone can make a frameset out of it, with the beautiful classic small tube look of my Surly Pacer frame and fork, for under a $600. Until that happens I’m not interested in carbon.

    For the record f1 cars run carbon suspension links and at the Monaco GP when the tap the walls the arms snap and the cars are done. During the steel suspension arm days they didn’t break they just bent leaving the car drivable.

  7. “We’ll let the arm chair engineers explain why this steel versus carbon failure test isn’t valid for cycling applications. Everyone else, please enjoy the science experiment.” – This is why I love BikeRumor. Keep up the good work folks, favorite cycling website by far

  8. If you’re comparing failures of frame materials based on a crash and how the material is going to potentially fail during the crash, you should be more concerned about what kind of helmet and other safety gear that’s going to protect you during said crash!

    I’ve worked at a few bike shops over the years and saw any and all frame materials fail, either due to abuse or a crash. How the frame material failed had little to do with how the rider fared afterwards. People on here and many other forums always say that they’d rather have a steel frame bend, instead of having a carbon fiber frame break into a bunch of shards of carbon fiber. Either way, you’re still looking at a frame failure and neither material is going to have an advantage during said failure with regards to the rider.

  9. I’m gonna guess that this was an apples and oranges comparison. Let’s say that steel driveshaft was made out of some exotic Columbus or Reynolds steel. What would happen then? I am sure that carbon has it’s place, but the difference between exotic steel and CF probably isn’t as big as that video shows.

  10. Articles titled like this is turning this site into the Fox News of bicycle journalism. C’mon guys, no need for the sensationalist titles.

    Clay, most likely no, even the strongest alloy steel won’t be stronger or near the weight of the CF one.

    That said, driveshafts only see torsional load, any compressive loads and the steel would prevail by quite a large margin. Of course a driveshaft *should* never see those loads, but it goes to illustrate that carbon isn’t the best for EVERY application.

  11. I’ve crashed and broke both a steel frame and a carbon one. The difference was that the carbon one costed half as much as the steel to repair… Another thing to think about.

  12. Good test for a drive shaft. Anyone at the cutting edge of this sport will tell you that carbon frames are superior. Everyone else is making excuses. I have a steel bike and a carbon one and like both, but I have no delusions about which is better.

  13. Guess all the arm chair inhabitants took the bait. Same guys who spend hours talking pre- and post-ride–bookending a 10-minute ride to the coffee shop.

  14. The problem is that lighter and stronger does not equal a better bike. It just equals as lighter one. So few of my rides have mountain top finishes.

  15. “We’ll let the arm chair engineers explain why this steel versus carbon failure test isn’t valid for cycling applications.”

    If anyone develops a product for armchair engineers, they better get some ad space on here. They will sell a $hit ton of widgets.

  16. I completely agree with the dude in the very first post of this thing. As someone who has a quiver of every frame material- steel, ti, and carbon, I would much prefer to be on a metal during a frame failure. The argument has been settled a long time ago. Carbon is by far the best option for racing, but steel has certain kind of soul or ‘je ne sais quoi’ that carbon will never achieve. I think this is why carbon dudes change out their bike’s every couple of years despite no tangible benefit.

  17. @Clay I love how you think “exotic” Columbus or Reynolds steel as a material is something special or vastly different in yield stength than run of the mill 41XX and 43XX Chromoly steel. All of the gains within steel design have to do forming the wall thicknesses to the minimal wall for the given part of the tube with a larger OD. Vast changes in steel metallurgy haven’t been made much in 50 years. The axle steel is actually a good analogy from a prospective of relative strength and type of material used in bike tubing. Argue about failure modes all you want, but it shows that carbon can be easily tailored to the application better than any other material.

  18. To see actual tests regarding how a bike will stand up to both normal use and crashes, you should go to Cannondale’s Q lab. They twist, and snap both their own frames and those of other manufactures. Their carbon holds up very well.

  19. The US Navy figured this out decades ago. I was on the USS Nimitz and their concern was how much torque (classified) can they put on the prop shafts without them snapping. Anyway, Engine #1 (the most forward on the ship) will turn 12.5 times before the propeller starts to turn. Each shaft can take 65,000 horsepower and not snap. Steel not CF.

  20. @Rick: That may have been true “decades ago” on the USS Nimitz. But that was decades ago, before widespread carbon fiber manufacturing had really taken hold, no? The US Navy, like many commercial marine end users, are now using carbon fiber propulsion shafts on new construction.

    My two cents (and yes, I’m an engineer. A PE at that) is ride what you like. You can build safe, reliable, fun to ride bikes in any material. My personal choice is titanium. But if your choice is carbon, sweet. If it’s steel, sweet. Heck, build ’em out of 3D printer resin or bamboo for all I care. The only unacceptable choice is not riding.

  21. I’m definitely not an engineer, but I have seen a couple of carbon failures on racing yachts. In both cases, the failure was not the result of the intended application, but the result of human error.

    The first was during the Admiral’s Cup about 20 years ago. I was prepping a boat for Cowes Week (a big sailing event here in the UK, usually with over a thousand competing yachts), when one of the competitors came into the yard. The boat had grounded – or rather, been dumped in heavy waves – onto a reef off the Isle of Wight, pushing the keel up through the bottom of the boat by around six inches, and knock the keel shoe (A ridiculous rule-bending piece of wood on the bottom of the keel) off in the process. Working overnight, about half a dozen of us got the boat up on chocks, dehumidified the interior, glassed over the cracks and replaced the keel shoe. The boat carried on competing for the entire event, including the Fastnet Race. As far as I know, it’s still going strong.

    Second was a couple of years ago when racing an X-35. The carbon spin pole must have been 8-10 inches in diameter and weighed about nothing. A poorly timed drop meant the kite got dropped into the water. The pole uplift was also released at the same time, and the pole dragged down onto the safety lines. The same sort of thing as snapping a branch over your knee, basically – and the pole did, in fact, snap like a twig. We got back on shore, ordered a new tube and borrowed an aluminium pole to race with the next day.

    In both cases, the use was fine – the pole’s only function was standing up to compression loads, as the fittings at each end took the brunt of the pole uplift and downhaul, and the sheet loads. Outside of that application, however, it perhaps wasn’t quite so tough. I’m pretty sure an aluminium pole would also have failed, by the way.

    Long story short: It’s not the loads you test for but the unexpected damage that is the worry.

    For the record, I happily run carbon bars and posts, and if I could spare it, would happily ride carbon rims and frames.

  22. That’s a filament wound shaft also the company in the video is Compton technology group not lotus I actually turned down a position there.
    Very few folk use filament wound there.stuff in bikes or at least it’s not as common, a roll wrapped shaft would not have lasted anywhere near so its not an apples and apples compare

  23. i am not an engineer, i am an aspiring “actor” however. What l do know about carbon is that it can be made super crazy strong! Carbon doesnt always need to be light. its light because less is needed to be strong/stiff as needed.

  24. @Jeffy
    You can buy a complete Trek 2300 or Specialized Allez Epic for less than $500 easy, and thats with the rest of the parts. They’re completely obsolete.

  25. @ddbaxte – you bring up a good point. ‘steel is real’ is a catchy phrase and has been around forever. the carbon marketing guys need to come up with something that establishes CF as a dominant material. ‘fiber makes you……..regular?’ wrong kind of fiber. ‘WTF ist CF’ (Werkstoff Top Faszination may have limited market appeal.).

  26. I see people die almost every weekend from crashing a carbon fiber frame and getting shards in their legs or failing to see a hairline fracture in the material. I also see people die a few times a year from crashing a carbon fiber bike and then not being able to ride it out and getting dehydrated. I also see people with chronic back problems because their forks and shock lose air and they have to ride bottomed out. Neither would happen with a rigid steel frame and fork.

    Oh, wait, I mixed up reality with my projected unfounded fears. Turns out, everything is dangerous and not 100% safe to some extent, but the key is realizing the probability of failure and the consequences of that failure. Like Zap pointed out- if you crash often and hard enough for this to really be a factor then by all means get a steel frame and a good brain for the tumble you take every week.

  27. I’m not sure why you’d want the classic looks of whippy old steel frames. There’s a reason why thinner and lighter oversized tubing like 853 is popular for high end customs.

  28. “Out for a Ride” – you see people die every weekend? What is it you do? Where the heck are you that you see people die every weekend? Basra? Basic road cycling is not a dangerous sport – carbon is still a fine choice – I’m not intending to jump taxi’s or take the stairs…..

  29. @James – take it easy, don’t you know who “Out for a ride” is…
    He is known by many names, you may know as, The Grim Reaper 🙂

  30. The issue is delamination and breakdown of epoxy due to UV and the elements in general. Even though the weave itself is stronger than steel, the way it’s held together can and will not ever be suitable for long-term use like steel. Even though manufacturers say this is no longer an issue because of their ‘UV protection epoxy’ etc they’re only true to an extent. And even though the carbon itself is ‘stiff’ the laminate is not and degrades over time due to stress or just exposure to elements. I forgot who, possibly porsche but definitely a major luxury vehicle company, did a test on all the worlds highest end carbon fiber and decided it was unsuitable for long-term use due to these reasons.

  31. Interesting video, but not the way they intended it to be. If those two tubes were bike frame tubes the steel bike frame would be bent and twisted but possibly still rideable after the tubing wall kinked. The carbon fiber shaft on the other hand snapped completely in two during it’s failure, meaning you’d be walking home or calling for a ride when the frame broke. With a steel frame if you ran head-on into something during a race like a fallen rider or a curb you’d probably put a nice kink into the bottom of the downtube where it meets the headtube. On a carbon bike you’d just wind up snapping the downtube off at the headtube/downtube junction, and probably snap the toptube off too, leaving you with a two-piece frame. The main difference between a metal frame that’s been damaged and a carbon one is that a metal frame is much easier to check for cracks or kinks resulting from a previous crash or stress cracks. The average person can buy a used metal frame or fork from Ebay or Craigslist and eyeball it for cracks or kinks from previous damage, with carbon the damage can be hidden internally inside the fabric itself and you’d never know. When carbon breaks it’s jagged and sharp as hell, which means you can get seriously injured just by falling on the broken parts, and there’s absolutely no structural strength to it in a secondary impact after it breaks. If a carbon fiber Indy or F1 car hits a wall the carbon breaks and flies apart, and if it keeps hitting things there’s no structural strength left to protect the driver. If a cromoly NASCAR chassis hits the wall it might get bent all to hell, but it still retains some structural strength in seconday impacts if another car hits it or it keeps hitting the track walls.

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