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  1. #1
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    Carbon vs aluminium bars?

    Hi. The other day I slammed my carbon bars against a rock, and the bars became cracked. A rider I met on the trails recommended aluminum bars over carbon because carbon bars tend to snap without warning. Is this true? should I go ahead and buy aluminum bars?

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    I avoid carbon on stems, bars and steerer tubes. Many will tell you they have no issues with any of these components. Until they do. Bike tips over at a stop by gust of wind. Pro told me to toss the bars in the trash. Carbon has one weakness which is sudden impacts can damage it and you may not even see it. Needs a sonic scan. As one gets much older, you tend to become more risk adverse. A failure to your bars, steerer or stem could result in death. Why take that risk? Rockshock SID uses carbon in the steerer and crown yet weighs more than the Fox 32 SC Factory. We all make our own choices so...Safe Travels All!

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    Either can snap, either can last forever.

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    You could try titanium bars, some great ones out there. I use Watson Cycles. Andrew bent my bars for me.

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    Any carbon part will always brake without warning, by the nature of the material. I went from alu to carbon bars on my fatbike and my experience is as following - with suspension fork the difference isn't really that big in my opinion. With rigid fork the difference is substantial, carbon absorbs all vibration from small bumps much better.

  6. #6
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    Quote Originally Posted by Black Squirrel View Post
    Either can snap, either can last forever.
    It's the failure mode that differs.

    Yes, carbon is very strong and in many respects much better than metal but it is susceptible to certain kinds of damage that can lead to catastrophic failure somewhere in the future. Maybe the distant future but the problem is that it's hard to predict.

    Metal will virtually always crack from the outside and it will either be visible before catastrophic failure or the failure will be progressive enough that you might have time to see it coming. Carbon lets go instantly. You don't get any warning.

  7. #7
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    Aluminum will also fail without warning if it is a fatigue failure. Simply over a certain period of time after enough cycles.

    Carbon will fail without warning, but it doesn't fatigue the same. It needs to be stressed to a failure point, at which time it suddenly let's go. If carbon is never taken beyond it's design spec, it won't "just fail" like aluminum.

  8. #8
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    You can watch BKXCs where his buddy crashes and snaps his carbon bars and the bar impales his thigh


    https://youtube/w2sMFZIB6zA
    Last edited by fiveo; 04-16-2018 at 11:58 AM.

  9. #9
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    Quote Originally Posted by Mr Pig View Post
    It's the failure mode that differs.
    ....
    Metal will virtually always crack from the outside and it will either be visible before catastrophic failure or the failure will be progressive enough that you might have time to see it coming. Carbon lets go instantly. You don't get any warning.
    No metal will not always crack from the outside, and it will not always be visible, as metals have differing crystal lattices which dictate the failure mode based on the kinetics of loading and material properties, which are driven by the metals microstructure.

    In my experiences of breaking Al handlebars, cranks (even modern next sl) and wheels in both materials the failure of carbon while often times catastrophic often leaves the broken part attached as carbon fiber is a complex matrix of epoxies and polymers and will be broken and dangling. I was able to keep riding when I snapped a carbon crank on the chainside, while on metal I crashed hard.

    I am of the opinion that carbon bars (35mm std in general really are too stiff for me, causes distinct hand numbness on rides over 30 miles) and alloy bars will given the same catastrophic load both fail. Only carbon may be dangling allowing for a more controlled crash.

    While both materials are used for similar products, their inherent material properties differ, metals are isotropic ( evenly distrbute load across structure regardless of loading direction) while composites are anisotropic (loading direction affects load propagation) making it difficult to create comparison testing regimens.

    TLDR: Research the engineering standards of the company making the part, composites require extensive FEA that add cost, manufacturing quality is key when evaluating composites.

    Buy what you like from a reputable manufacturer and ride til the wheels fall off.

  10. #10
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    Quote Originally Posted by Velocipedist View Post
    Buy what you like from a reputable manufacturer and ride til the wheels fall off.
    I'd rather not!

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    Aluminum will not fatigue failure unless there is an underlying crack initiator, like from a previous impact.

    Given enough load both can fail catastrophicly without warning, but that is highly unlikely to happen in both systems without a precursor impact that initiated the fatigue/failure.

    Which is to say they both will fail under similar extreme loading. Less than those loads and I would consider personal riding style and trail character to decide.

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    It seems like a lot of carbon bar failures are due to the stem or brake levers being over torqued. I think if everything is properly torqued I don't see any reason why carbon bars would be unsafe. I'd replace the bars after any hard impact.

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    Carbon is susceptible to impact from sharp objects like rocks during a crash. The pros are that it's lighter and vibration dampening, the big con is that it fails with high load in a small area (i.e. rock impact).

    Aluminum is certainly not indestructible either but usually dents before cracking, and in the real world it seems to be more impact-resistant than carbon, especially when it comes to handle bars. But it is a bit heavier and has less vibration dampening properties. On an AM bike, personally, that doesn't bother me because I have suspension and grips to dampen vibration.

  14. #14
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    Quote Originally Posted by kpdemello View Post
    Carbon is susceptible to impact from sharp objects like rocks during a crash. The pros are that it's lighter and vibration dampening, the big con is that it fails with high load in a small area (i.e. rock impact).

    Aluminum is certainly not indestructible either but usually dents before cracking, and in the real world it seems to be more impact-resistant than carbon, especially when it comes to handle bars. But it is a bit heavier and has less vibration dampening properties. On an AM bike, personally, that doesn't bother me because I have suspension and grips to dampen vibration.
    10 years ago I would have agreed with this 100% but there have been enough advancements in composite technology that this is no longer true. The impact resistance has gone up immensely as of late in large part due to bonding agents, crosslinker catalysts and resin and fiber improvements. There's even a company doing new thermoplastic resins with the light weight of epoxy thermosets so... technology is advancing believe it or not! I run carbon bars now and won't ever go back; they are just flat out several magnitudes stronger than any aluminum bar and that now includes AFTER crashes. I'm a supplier to these manufacturers so I know the technology advancements. It's an exciting time but the low costs are over; you can expect to pay double for carbon fiber anything within a year as resin prices are skyrocketing out of control (I lost a big aerospace order today in fact). If anyone is in the industry, or would like to learn more about composites, I strongly suggest attending SAMPE in Long Beach May 22-23rd. I will be exhibiting there and would be glad to meet up.

    Have FUN!

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  15. #15
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    Quote Originally Posted by Gman086 View Post
    10 years ago I would have agreed with this 100% but there have been enough advancements in composite technology that this is no longer true.
    I'm sure what you are saying is true, and I'm sure the quality will keep getting better, but at the moment it's hard to know exactly what you are buying. The market will be a eclectic mix of great carbon right down to the junk from China and how can we tell what's what? Obviously, buying from a big brand helps but I've seen high-profile issues even from them.

    There are other issues. Production of carbon composites is dirty and the material can't be recycled as yet, which might become more of an issues as usage increases. It might be the future but for now I'm sticking with what I know.

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    That's my concern - how do I know what I'm getting?

    The other major factor for me is cost. I've ridden aluminum stuff for decades with good results. I'm reluctant to switch unless I'm getting a real significant advantage, and last year when I was looking, the difference between a carbon frame and an aluminum one was only 1 lb. Not worth the $700 price difference for me.

  17. #17
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    Quote Originally Posted by kpdemello View Post
    The other major factor for me is cost. I've ridden aluminum stuff for decades with good results. I'm reluctant to switch unless I'm getting a real significant advantage...
    Just develop the vanity and stupidity of some of the weight-whinies. Keeping the lights on in Chinese crap-factories, someone has to.

  18. #18
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    I'm moving in the opposite direction. Been looking at 26" steel hardtail frames lately... talk me out of it.

  19. #19
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    the only carbon bars, seatposts, or wheels I will use, are from top manufacturers who've been doing it for many years. no way will I roll the dice on carbon, since literally anyone with a can of resin, plastic sheets, and a vacuum can make carbon stuff that looks fantastic, but unknown and untested strength

    all the cheap stuff you can find ? no f'in way

    stems for me, aluminum. cranks aluminum. pedal bodies aluminum
    steerers ? aluminum there too.

    bars CF, seatpost CF, wheels CF, frame CF

    anyhow I am a fan of easton bars because they have been doing this for-ever and are a sure bet.

    now, for road bike, all that can be cf since I am not bashing it against anything and the steerer and stem are not taking hits, just whatever my arms can beef out when climbing.
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  20. #20
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    Quote Originally Posted by kpdemello View Post
    Carbon is susceptible to impact from sharp objects like rocks during a crash. The pros are that it's lighter and vibration dampening, the big con is that it fails with high load in a small area (i.e. rock impact).

    Quote Originally Posted by Gman086 View Post
    10 years ago I would have agreed with this 100% but there have been enough advancements in composite technology that this is no longer true.
    You're both partly right. Carbon is typically weaker on impact damage. However it can be stronger than all other at impact damage if it was designed for that environment. In cycling, it is generally not designed for impact damage due to weight! Another point that I think is a positive is that carbon is generally easy to repair or repair is very possible in most cases. With alu it is almost prohibitive due to the heat treating process unless one has access to the capability.

    That said when it comes to bars, I stick to the top name brands vs china carbon just for the safety aspect. And I would always go for carbon on bars where it can have the most positive impact on your fatigue.



  21. #21
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    Id trust $20 aluminum bars. I think that's the main difference these days.

    I think santa cruz pretty much put the impact resistance thing to bed.

  22. #22
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    Quote Originally Posted by VenomousDancer1234 View Post
    Hi. The other day I slammed my carbon bars against a rock, and the bars became cracked. A rider I met on the trails recommended aluminum bars over carbon because carbon bars tend to snap without warning. Is this true? should I go ahead and buy aluminum bars?
    I would replace the bar since it is cracked. Both work. If you are more comfortable with the idea of aluminum bars, get them. Peace of mind has value.

  23. #23
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    Since it's cracked, your safest bet is to toss it. If its scratched, thats a different story, but even still, safest to toss it. The majority of carbon failures out there are from either over-torquing the brake leves and shifter, or from a crash that effectively doing the same, causing a stress crack where the brake or shifter clamps are. That said, Ive personally tested at least two dozen carbon handlebars with the stomp test, where I grab two lengths of 6x6 lumber, and bridge the handlebar between them. I then proceed to jump and stomp on the bars with all 230+ Lbs in an effort to break them as you would a tree branch. Better they break in the garage, than break on the trail and leave me missing half my face. All in all, only one bar has ever failed this test, a chinese carbon bar branded "asiacom". The dozen or so other chinese carbon bars all passed, though you get a feel for which ones seem laughably flimsy compared to my favored raceface sixc bars.

    Anyway, I will continue to run carbon, but these days, only name brand carbon, and usually AM/DH rated bars. I always do a stomp test. Just watch your ankles if you choose to test yourself.

  24. #24
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    ^^I have a broken Easton CNT bar from over clamping that I still keep to use as a breaker bar. It's strong as hell and been going strong as a breaker bar for two years. I never bothered to clean the original cracked area doh, I should have cut the break clean which would have spread the breaker forces evenly. Maybe later I will dremel the broken area clean to preserve my breaker bar lol.

  25. #25
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    OH yeah overclamping

    I make sure all controls attached to the bar at 7nm, and stem clamp bolts are 5.5nm
    no more than that. consistent correct torque is critical to carbon bar survivability.

    that, and not wreckin
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  26. #26
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    Just get Race Face Atlas Al bars and never worry about your bars failing.

    I was a carbon hold out for years but eventually warmed up to a carbon frame and even carbon cranks but I just don't trust carbon bars over my trusty Race Face Al ones.
    2016 Santa Cruz Hightower 29er
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  27. #27
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    Quote Originally Posted by Mr Pig View Post
    I'm sure what you are saying is true, and I'm sure the quality will keep getting better, but at the moment it's hard to know exactly what you are buying. The market will be a eclectic mix of great carbon right down to the junk from China and how can we tell what's what? Obviously, buying from a big brand helps but I've seen high-profile issues even from them.

    There are other issues. Production of carbon composites is dirty and the material can't be recycled as yet, which might become more of an issues as usage increases. It might be the future but for now I'm sticking with what I know.
    Thatís true, I should have qualified my info - only the higher quality composites have the advancements. My advice is you pretty much get what you pay for... most higher priced bars and frames are using the latest technology. But yeah, I donít blame you for your skepticism or sticking with what you know.

    You make a great point about recycling but, believe it or not, one of my customers is VERY successful with this and converts thermoset garbage into thermoplastics with unbelievable impact resistance! Connora Technologies: RECYCLING ‚Äď Connora Composites
    This really is an exciting time in the Advanced Materials Industry!

    Have FUN!

    G MAN
    "There's two shuttles, one to the top and one to the hospital" I LOVE this place!!!

  28. #28
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    Actually carbon fiber can be recycled. Trek for example recycles all of their excess carbon, broken carbon ie. warranties, they will take whole frames and break it down. Their policy is to recycle everything.

    You can see this in the video where GCN tours the Trek Waterloo factory.

  29. #29
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    Quote Originally Posted by VenomousDancer1234 View Post
    A rider I met on the trails recommended aluminum bars over carbon because carbon bars tend to snap without warning. Is this true?
    No, it's not true.

    I've broken my fair share of carbon over the years and there was never any doubt that it was in the process of breaking, and when it broke it didn't snap in half.

    Protip - if you're riding carbon and you hear a *pop* on the trail, that was not a rock hitting your frame. That was carbon telling you that part of its structure just gave out.

    But I guess if you ride with loud music and never pay attention to what's going on with your bike or inspect it at all, then it could happen "without warning".

    And yes, you should replace your bars. That crack? That's called a "warning".

  30. #30
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    Quote Originally Posted by Schulze View Post

    Protip - if you're riding carbon and you hear a *pop* on the trail, that was not a rock hitting your frame. That was carbon telling you that part of its structure just gave out.


    unless it's a rock hitting your frame
    I brake for stinkbugs

  31. #31
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    Quote Originally Posted by GuitsBoy View Post
    Since it's cracked, your safest bet is to toss it. If its scratched, thats a different story, but even still, safest to toss it. The majority of carbon failures out there are from either over-torquing the brake leves and shifter, or from a crash that effectively doing the same, causing a stress crack where the brake or shifter clamps are. That said, Ive personally tested at least two dozen carbon handlebars with the stomp test, where I grab two lengths of 6x6 lumber, and bridge the handlebar between them. I then proceed to jump and stomp on the bars with all 230+ Lbs in an effort to break them as you would a tree branch. Better they break in the garage, than break on the trail and leave me missing half my face. All in all, only one bar has ever failed this test, a chinese carbon bar branded "asiacom". The dozen or so other chinese carbon bars all passed, though you get a feel for which ones seem laughably flimsy compared to my favored raceface sixc bars.

    Anyway, I will continue to run carbon, but these days, only name brand carbon, and usually AM/DH rated bars. I always do a stomp test. Just watch your ankles if you choose to test yourself.
    Iím with you in regard to carbon. Only buy the trusted brands. I also have derby wheels that are wonderful and I run those on a steel frame.

    For the frames and cranks, I love metal. Itís not necessarily anything else but feel.


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  32. #32
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    Quote Originally Posted by Gman086 View Post
    This really is an exciting time in the Advanced Materials Industry!
    It must be.

  33. #33
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    Quote Originally Posted by VenomousDancer1234 View Post
    Hi. The other day I slammed my carbon bars against a rock, and the bars became cracked.
    Anything will break without warning if you hit it hard enough!

    On a less pedantic note, I've seen plenty and Alu, carbon and even steel bars snapped clean in two. There is usually a story behind it that goes beyond 'it just broke one day,' and involves a crash or some optimistic huck to flat, or several.

    Most modern bars will crack or bend before they completely give out, as you have experienced. As for which you should buy, I have a large collection of alloy Renthal bars, because I like the shape of them. Beyond that any bar from a known brand will do nicely.

  34. #34
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    Quote Originally Posted by J.B. Weld View Post
    unless it's a rock hitting your frame
    In which case you should ignore the pop.

  35. #35
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    Quote Originally Posted by thesmokingman View Post
    In which case you should ignore the pop.


    Of course, what else?
    I brake for stinkbugs

  36. #36
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    Quote Originally Posted by J.B. Weld View Post
    Of course, what else?
    Stop, get off the bike and push it into a creek. Go buy a new bike. No sense riding a bike that might have scratched paint.

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