How "proven" are carbon fiber forks and carbon fiber seat stays?
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  1. #1

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    How "proven" are carbon fiber forks and carbon fiber seat stays?

    I'm new to the world of cyclocross bikes and was curious how proven (for durability) are carbon fiber forks and seat stays? Have they been incorporated on these bikes for awhile now or are these new features to help lighten the bikes and improve their comfort?

    I would hate to drop $2000 for one of these high end bikes and then have durability issues with the carbon fiber. I watch a lot of F1 and those cars have a lot of cf parts, and when they break, they fail big time and just shatter. That'd suck on a bike, IMHO.

    Any insight?

  2. #2
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    They don't just snap
    remember. Plenty of CF MTB frames are out there. Every fork will differ as companies use diffrent tech. I've never seen one break in a race but like all equipment, there will be some that fail.

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    Quote Originally Posted by dfleck
    They don't just snap
    remember. Plenty of CF MTB frames are out there. Every fork will differ as companies use diffrent tech. I've never seen one break in a race but like all equipment, there will be some that fail.
    Carbon fiber mountain bikes a relatively new phenomenon. 1-2 years ago I don't think you could find anybody outside of maybe Kestrel making them. Now many of the biggies have jumped on board, but I just wonder how proven the material is.

    As for how they break, I know when a carbon fiber suspension part on an F1 car breaks, it tends to just snap (or fail catastrphically). Are mountain bike parts made from CF designed or made in a different way to allow them to not fail so dramatically.

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    I have seen carbon bars and seatposts break, and Trebon had bar slipage probs in Boulder. I have seen the pics of Nys' C50 broken from crashing, also seen plenty of Alu/Steel frame brake too. Trebon/Wicks/Caveman run carbon rear ends, Spcialized has midlevel bikes with carbon rear, Haven't seen them break, no recall notices that I am aware of. Carbon forks are everywere,
    I am not one to think that Cross bikes take MORE stress than road bikes, its just different forces/frequencies. (I am not an Engineer) Dfleck makes a good point about carbon MTBs, thats prob a better comparison of forces to cross, and not a whole lot of problems.
    If you WANT a carbon rear end, get one, wether or not you NEED one is a different thread. Carbon forks are well proven.
    If your beer isn't Belgian you ain't racin' 'Cross!

  5. #5
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    Quote Originally Posted by ajoc_prez
    Carbon fiber mountain bikes a relatively new phenomenon. 1-2 years ago I don't think you could find anybody outside of maybe Kestrel making them.
    What about the Trek OCLVs and Giant's xtc carbon? they've been around forever

  6. #6
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    Carbon can built to be very strong -- stronger than aluminum or steel -- and has been incorporated into road, CX and MTBs for several years. I think they have been proven at least a safe as any other material. If you are wary of the relatively recent adoption of CF for MTBs, consider the number of road forks that are out there on crit bikes and hitting rocks on 50mph+ road descents. I would not worry about a frame or fork "exploding" under you due to normal racing or riding.

    However, a single crash, even a minor one, can total your frame or fork if you land the wrong way on the wrong piece of terrain. Once weakend just so, you can have a catastrophic failure at an underterminable point in the future. The rub is that it is it is very difficult to discern whether a part has been significantly damaged.

    I'd say, if you are going to lose sleep over the remote possibility of component failure, or if you can't or don't want to replace parts that might be damaged, avoid CF. I have a full steel race bike and a AL/CF race bike and the difference is negligible.

  7. #7

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    Quote Originally Posted by ajoc_prez
    Carbon fiber mountain bikes a relatively new phenomenon. 1-2 years ago I don't think you could find anybody outside of maybe Kestrel making them. .
    That sould really be said "10 to 12 years ago" and "Kestrel was making crap" and to include the "Treks that were Lugged carbon (mtn and Road) and OCLVs that the Texan won all those tours on,and the C40s that had already won Wolrd Cup races on the road, and the ALAN/Geurciotti Carbon cross bikes that were being raced, ok I'll stop...
    If your beer isn't Belgian you ain't racin' 'Cross!

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    Watching the elite race at CX nats there was a rider in the elite field that crashed hard on the downhill into the Clif Bar run up. His steerer tube catastrophically failed and he went down like a ton of bricks and stunned himself good. It was a carbon fork but I did not see if it was an aluminum or carbon steerer. If damaged, either are going to be just as likely to fail and both will be catastrophic.

    I'm not sure what the cause of the break was but if it was a carbon steerer the few that I have seen are typically from over tightening of the stem bolts and compression of the carbon. It's likely this could have been the case here too, but I can't say. If you have any carbon fiber parts that are under compression from a clamp (stem, seatpost, etc.) you need a torque wrench to set the bolts.

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    I guess carbon fiber has been around for awhile in the MTB world. I had forgot about some of the Trek bikes. I guess it is just now tricking down to the less expensive bikes. I don't have any experience with road bikes, and I've just been researching cyclocross bikes recently, so wasnt sure how new CF was..

    I'm a big fan of steel...if I'm not mistaken, it will normally bend before it breaks. Maybe I'm making too big of a deal about this, but just thinking back to the problems F1 has with CF failing, it got me to thinking about it. And then there is possibility of damaging the carbon fiber in a crash and then wondering if it was severe enough to write off the frame. While looking at a $6000 carbon fiber mountain bike at the LBS, I was thinking how much it would suck to crash and dent the frame, then wonder if you were going to have to replace it OUCH!!

    Off to do more research... thanks for all the input so far

  10. #10
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    Just cause it's not carbon doesn't mean it wont snap


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    Quote Originally Posted by CabDoctor
    Just cause it's not carbon doesn't mean it wont snap

    What are those Bianchi's made from? Steel? Aluminum?

  12. #12
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    Quote Originally Posted by AABCCX
    It was a carbon fork but I did not see if it was an aluminum or carbon steerer.
    It was an aluminum steerer, and it brok about an inch north of the crown, basically in the middle of the head tube somewhere. He's had that bike for about a month.
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    I'm guessing aluminum but don't quote me

  14. #14
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    Quote Originally Posted by ajoc_prez
    What are those Bianchi's made from? Steel? Aluminum?
    That is definitely an older steel model (much like the one i have).

    And regarding the F1 racers - the car is designed to disintegrate. It is meant to keep the driver safe at 200+mph while sacrificing the car. A bit different design problem than a race bike.

    -D

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    come'on guys that Bianchi is Aluminum, look at the size of the welds(the one that failed) and the diameter of the tubes.
    If your beer isn't Belgian you ain't racin' 'Cross!

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    Quote Originally Posted by damon
    And regarding the F1 racers - the car is designed to disintegrate. It is meant to keep the driver safe at 200+mph while sacrificing the car. A bit different design problem than a race bike.

    -D
    Actually I was referring more to the suspension pieces than the tub of the car. The CF suspension on those cars tend to be very delicate and even if they rub wheels with another driver, it can cause problems. I've even seen a few fail for no reason at high speed. Scary stuff. Granted, bike parts are probably a little different, but I was just curious if CF has been on bikes long enough for us to know its durability...sounds like it has.

  17. #17
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    Quote Originally Posted by myette10
    It was an aluminum steerer, and it brok about an inch north of the crown, basically in the middle of the head tube somewhere. He's had that bike for about a month.
    Hope he's alright. That was quite a hit he took.

    Any idea what kind of fork?

  18. #18
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    Quote Originally Posted by ajoc_prez
    Actually I was referring more to the suspension pieces than the tub of the car. The CF suspension on those cars tend to be very delicate and even if they rub wheels with another driver, it can cause problems. I've even seen a few fail for no reason at high speed. Scary stuff. Granted, bike parts are probably a little different, but I was just curious if CF has been on bikes long enough for us to know its durability...sounds like it has.
    I'd say that carbon has been around long enough on MTBs to prove durability.

    I've got a '95 Fisher (aka Trek) OCLV carbon hardtail mtb. I thrashed that bike as hard as any bike I've owned (steel, Al, or Ti) and it took it all just fine...jumps, drops etc.... The bike is still going strong doing singlespeed duty.

    I can't count the number of times I had really large rocks flip up and bash into the downtube. It was enough to make me cringe, but never caused any problems.

    And as for carbon failing catostrophically, I've broken a carbon seatpost and a carbon crank, and while both failed, neither one let go without warning. They both started crackling well before they failed.

    Also had a friend break a CF frame, and it also gave warning.

    Remember that carbon is typically formed with multiple layers of cloth with the fibers often oreinted in varying directions. A crack has to get through all of those layers for the entire part to fail. In both failures I had, I believe the crackling noises I heard was the first layers starting to give way. Everntually the others let go, but not without warning.

    I've got a friend who'se aluminum road bar snapped without warning sending him to the ground ending with a bunch of pins in his elbow. Maybe there was a crack visible at some point, but I highly doubt most riders inspect there bikes for cracks. So in that respect, aluminum doesn't necessarily give any warning.

    As far as part failure, aluminum doenst give me any more confidence than CF. Bonding points between materials (say between a carbon fork and aluminum steerer) is what worries me more than the carbon failing.

    And as for carbon steerers failing from overtightening....well......that's why I work on my own bikes and nobody else touches it.

  19. #19
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    If it were controlled closely and two bikes were made to identical specs, one being steel and one being carbon fiber composite would there be a fundamental difference? It depends on a lot of variables. Obviously carbon composites can be engineered to be very strong (the 787 brakes are carbon fiber because it offers benefits over previous brake materials used on planes). There is a paraplegic athlete that uses a carbon fiber leg that acts like a spring.

    Only in the uber-light category of bikes would I be wary of a bike being fragile. Bike manufacturers do not want to be sued out of business. There is no motivation for any company to put out a product of any kind, such as a bike, that is not strong enough to be nearly idiot proof. There is just too much risk.

    Why we see forks made of carbon fiber vs steel or titanium on many bikes is because the engineering specifications of a bicycle fork favor carbon as being the best material. While steel can be used successfully it is much more difficult to design a fork that would be light, yet compliant in one plane and stiff in another.

    Get what floats your boat.

  20. #20
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    ^^Thanks for waking up this 7 year old thread.
    We have all been waitng 7 years for you to arrive, Oh Great Sage

  21. #21
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    Quote Originally Posted by the mayor View Post
    ^^Thanks for waking up this 7 year old thread.
    We have all been waitng 7 years for you to arrive, Oh Great Sage
    yet, today the debates still continue.

  22. #22
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    1. carbon fiber seat stays are mostly just public idiocy exploited by companies offering what the general public wants to buy. nobody will blame the company for selling that stuff. the benefit of the doubt always serves well.

    2. carbon fibre parts are lighter than their alloy counterparts. OR they are more durable for the same weight. that's a generalization, i know, it depends on the manufacture, not only the technology available.

    3. if you are looking for having the best durability look somewhere else (good quality steel tubing and welding). it would mean you don't need the same stiffness factor or the low weight but rather would want to minimize the risk of crashing as result of some crack developing without you being able to detect it. i prefer carbon forks for having enormous rigidity where i like it and i know the risk of having cracks appearing there for reason of some improbable impact are as low as possible. torsional and lateral rigidity for having as precise as possible steering in crazy traffic and poor road conditions are highly respectable. zero accidents means higher comfort to me.

    4. as a choice of selection, carbon fibre tubes have - from my point of view - the only appreciated benefit as to decrease the risk of accident and the better handling of the bike when no real pedalling torque is there. as soon as serious pedalling torque is applied, like on long trips with less concentrated mental effort, carbon remains with only the second benefit: weight (not too much aprreciated by me as i'm not a maniac into mountain climbing and i don't seek to perform as many tricks as possible on the city road).

    what i should always consider better as an upgrade over the scapin eos 7 i am exploiting right now would be a custom steel tubing with only the seat tube and the fork legs made of carbon fibre. carbon fibre fork legs i already have. it's just that i really don't want an 'upgrade' with seatstays carbon fibre but would only (slightly more) appreciate a carbon seat tube part of the frame. and that's it.

    ---
    so, on cyclocross you shouldnt get too fuzzy with carbon being an improperly selected tubing. it's great. just be sure to avoid denting impacts and use some large tires as carbon fibre doesn't manage high amplitude shocks too well but rather higher frequency and lower loads.
    Last edited by adipe12; 12-11-2013 at 08:47 PM.

  23. #23
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    The short answer to any of the 'is X good enough to race on?' is 'if you can't afford to replace it, don't race it.'

    Crashes and other 'stuff' happens. Especially in CX.

    ...and ya gotta remember: if you go off-road ya gotta pay to play. That includes CX.

    M
    I've moved back to NoVA. PLEASE change the weather!

  24. #24
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    How "proven" are carbon fiber forks and carbon fiber seat stays?

    Since its back at the top...

    I recently snapped a CF seat post on my cx bike during a botched remount. I opted to swap it out for a Thomson, but have no qualms continuing to use the CF posts on my road and TT bikes.

  25. #25
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    Quote Originally Posted by Insight Homewood View Post
    yet, today the debates still continue.
    What percentage of the carbon fiber forks and components made in 2006 have spontaneously exploded, killing the cyclist?

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