For sure, carbon fiber has been a huge boon for the development of lightweight, high performance bikes. But unlike the metal bikes before them, damage to a carbon component is not so easy to detect & their failure after being damaged is even harder to predict. So Belgian startup REIN4CED has developed a new type of carbon composite, reinforced with steel fibers. The new composite remains lightweight & flexible to build with, but results in a material with better impact resistance and improved integrity following local damage.

REIN4CED steel-fiber impact-resistant carbon composite

courtesy of REIN4CED

For many cyclists, perceived fragility and the often catastrophic failure mode of tradition carbon fiber remains off-putting. While carbon construction methods have improved by leaps and bounds over the last decade or so, we still occasionally see a carbon component explode or see one recalled due to increased risk of failure. Sure, for the most part failures  result from specific crash damage. Or parts fail from stress beyond a component’s design intent, or sometimes just a manufacturing issue. But that fragility or ‘fear of failure’ has limited carbon application. And it has meant that carbon fiber seems less appropriate in the eyes of many cyclists for day-to-day commuting bikes or those expected to get more regular abuse.

So that’s where REIN4CED’s steel-reinforced carbon composite comes in. REIN4CED developed the material based on research into a more ductile and damage-resistant composite. The resulting steel-reinforced composite is much more durable than a typical carbon+resin composite. At the same time it retains light weight and similar structural characteristics. Put simply, REIN4CED inserts a small amount of “dedicatedly developed steel fibers applied on specific locations in the material”.

The result is that the new REIN4CED composite acts more like a metal following an impact than traditional carbon. Hit it with something and you get a local and visible dent that “barely reduces the frame strength”. With most of structural integrity intact, sudden frame failure instance should decrease. And damage becomes more easily detectable so a cyclist will know that a part needs to be repaired or replaced.

Building bikes from REIN4CED steel-carbon composite

The trick to it all seems to be the automated material production. Mixing the steel fibers into the matrix yields the added impact resistance benefit without significantly impacting weight or workability of something like a prepreg raw material. Conventional carbon production remains very separate of the actual product manufacturing. But, it seems that REIN4CED requires a more closely combined production process. So together with the material they have developed a fully automated manufacturing process that would start with the raw carbon, steel & resin materials and output the final frame or fork, for example. So they have already started to work with a few bike brands. And are now looking to ramp up some new European production soon.

The most recent news is that REIN4CED has just acquired a big influx of funding. They are now tasked with setting up their pilot production plant in Belgium in 2018, making what they are calling “unbreakable composite bicycle frames”


  1. This is pretty cool. Some particular brands are notorious for breaking (whatever you do, don’t bottom out that Yeti!) Transition went back to alloy with their latest bikes and speaking to a dealer it is supposedly because they were having problems with rear triangle breakage and overall don’t see any big performance advantages for carbon over alloy.

    I have seen a ton of patched frames on the enduro circuit, which is perhaps an advantage of carbon. Does this affect the ability to patch/repair carbon?

  2. No mention of price or weight increase.
    The parts are still ‘broken’ (so not ‘unbreakable’ at all)
    Looks like this just makes damage harder to detect. And this is good?
    This is not a fix for the (usually) bad designs that result in recalls

    • don’t think there will be much of a increase in weight with spot treatment. but you are correct, damage would be impossibly hard to detect at times additionally repairs would not be possible.

  3. Neat stuff. However, I think there is a common misconception that carbon has low impact resistance… Sure, a super-thin 1.5lb road frame might have a few serious ‘weak spots’, but by-and-large carbon is super tough and difficult to break. Spent years in shops hammering on and otherwise smashing carbon parts, and most will take a ball peen hammer or bat swing repeatedly before failing. I am Pretty sure a well designed and slightly heavier carbon part doesn’t need steel to be strong.

    • When I cut the steerer off my all carbon RS Blackbox fork, I gave the cut off tube about 4 serious hits with a small metal hammer. Couldn’t detect any issue although that things has a 3/16″ wall thickness

    • @fred you are assume every frame is made equally which is not the case. some frames have impact protection and some don’t. even with that a rock impact at the right angle and force will be take your frame out.

      • Well don’t you wish all these bike companies would tell us more about their products instead of fluffing consumers up with buzzwords…
        “our confidence inspiring high-mod plus endurance gravel road cross frame is vertically compliant with all the fat confidence inspiring boost gravel bb845 supple sidewall columbus plus gravel”

  4. For the haters, think beyond the now. This could allow for a stupid light frame, while still providing confidence in the consumer’s mind. Or handlbars. Or cranks. A possibility is that manufacturers would not have to over-build carbon parts for impact strength or fatigue as carbon bits are built now.

    • Agreed, it may find it’s way into frames or cranks or some part we haven’t invented yet. People can thank materials tech for a staggering amount of stuff they enjoy, biking or otherwise, and to say, “What we have is good enough, quit looking,” is insane.

    • Or Innegra, for that matter.

      From where I’m sitting I see Dyneema more used on clothing…haven’t seen the material used in a carbon fiber composite yet. Perhaps I haven’t been looking hard enough.

  5. The most common steel-reinforced composite is concrete. And the most common problem is that any crack that lets water in causes the steel to rust and expand, which causes further damage to the concrete. At least CF has much greater tensile strength than cement and hence doesn’t crack nearly as much, but the damage shown above would let water in. Ironically a solution to this problem in concrete is to use glass (carbon is too expensive) fiber reinforcement instead of steel. But this creates problems due to low ductility, which is a big advantage of steel and why it is being added to CF as discussed above in the first place.

    • This carbon/steel composite isn’t made to allow you to ride with blown out carbon fork back home. It is made not to kill you when such an event happens.

  6. Did they just completely forget about Kevlar? Kevlar/carbon fabrics have been used specifically for this application for decades. Sometimes the wheel just needs to be reinvented…

    • Every material has its pro’s and con’s. Just because kevlar reinforced CF exists, doesn’t mean there aren’t applications in which this tech may be beneficial.
      Furthermore, the existence of this product does not prevent anyone from using other CF reinforcement methods, kevlar or other. Nor does the existence of this product require that all your CF products be made of it and it definitely does not require you to buy or invest in it.

  7. This could add further improvements to bump compliance on road frames. Currently, CF has to be to some extent over engineered to reduce the possibility of a catastrophic failure. If the steel fiber reduces the likelihood you can design frames to be more compliant and potentially responsive (i.e., the right amount of flex). For example a thin walled steel fork will still outperform a carbon fork as the carbon fork has to be “over-engineered” to some degree.

    This could actually be an important advancement for endurance and gravel bikes.

    • “For example a thin walled steel fork will still outperform a carbon fork as the carbon fork has to be “over-engineered” to some degree.”

      Actually it sounds quite the opposite on many bikes. From what I understand, the industry has a hard time building steel forks for disc brakes that aren’t boat anchors yet pass the euro safety test.

  8. Having talked to Rein4ced and seen their fork, I don’t think this will lead to much lighter products or better compliance. Today’s products are already very close to the limit of what is possible with the properties of carbon, and the properties in terms of strength, stiffness and elongation will not be any better with rein4ced. What is better is what happens after the carbon fibers fail, as the product will not fall apart an keep an astonishing amount of strength. The plastic deformation also means detection of failure is possible before catastrophic failure. So products get safer without much added weight.
    The adavantage compared to Dyneema, aramid etc. is that they are not much more than added weight in a product until failure, because their modulus is very low. Steel on the other hand has a quite high modulus, so it helps for strength and stiffness.

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