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Shifting Trends III: What Bikes are Made Of

Reading Time: 4 minutes

The performance of a bike varies dramatically, based on what its made out of⁠, and over the course of history they’ve been built out of just about everything. In the early days⁠—long before the pneumatic tire and the chain drive⁠—experimental versions of bikes were constructed out of wood and fitted with unwieldy cast iron wheels. For obvious reasons, that design was soon replaced by a lighter and more manageable version.

That type of swift design change happened often back then. In fact, early incarnations of bikes were basically redesigned from the ground up with every generation. In the end, it took the better half of a century to change the bicycle from a cumbersome, haphazard contraption into an efficient form of transportation.

That spirit of innovation has remained at the heart of the bike world ever since. Every year, we see pioneering new designs at industry trade shows. Frames made of bamboo, wheels constructed out of graphene, ceramic pedals, 3D-printed seats… The list goes on. And that’s one of the things that makes bikes awesome— there is no “right” way to make one. Their design and construction processes are endlessly malleable.

Steel is Real

When wood and iron were phased out in the late 1800’s, steel became the most popular replacement. Advancements in manufacturing allowed for more efficient production, and during this time, steel bicycles were first mass produced. While steel bikes are still made today, they have little in common with the early steel frames. The walls of the tubing was much thicker back then, which made the frame strong but also extremely heavy. The first steel bikes typically weighed 80 pounds or more!

Aside from the weight, construction methods were also different. Instead of welding the tubes together, as is the prevailing process today, old frames featured lugged construction. This process involved brazing the joints using fabricated external fittings. After the tube was inserted into the fitting (or lug), the surface area was covered with a molten filler material, like silver or brass. The hot metal fused the joints, seeping down into the gaps via a process called “capillary action,” and greatly increased the strength of the joint.

Lugged construction was only replaced relatively recently. When common building materials shifted from steel to aluminum and carbon fiber, so too did the building process.

The Reign of Carbon

Originally developed for aerospace application in the 1960’s, carbon fiber soon found its way to the bike industry. Noted for its high tensile strength and astoundingly low weight, carbon fiber quickly became attractive to bicycle manufacturers. But along with its assets, carbon production also presents a unique set of obstacles. For one, the construction process is painstakingly meticulous.

A carbon fiber bike begins its life as a single strand of filament, a material called polyacrylonitrile (PAN), which is not dissimilar to fishing line. PAN is baked, making it as pure, lightweight, and stiff as possible. The fibers are then treated by resin epoxy, a tough binding agent. This glue-like material fills in the gaps between the fibers, and improves the integrity. Once the carbon fiber is formed into sheets and layered with yet more resin, it gets laid up in a heated mold and pressurized to form the shape of the frame.

Since carbon fiber frames consist of millions of little fibers braided together, the job of the resin is very important. It can take only a minor blemish for the bike’s integrity to be compromised. Once the weave is broken, the fibers can continue to unravel, causing the frame to fail if the blemish isn’t repaired. That’s why it’s important to note that not all carbon is created equal. As the classic bike industry saying goes, “You can make a bike strong, lightweight, or cheap. Pick two.” For carbon fiber to be strong and lightweight, it must also be pricey. Lots of components are lightweight and cheap, but their integrity is questionable. If you’re considering purchasing a carbon fiber bike or wheelset, it’s always a good idea to do some research into the manufacturing process behind the product, and if a deal seems too good to be true, it probably is.

Where Does it Go From Here?

It’s anyone’s guess what bikes will be made of in the next couple decades. We can, however, posit that they will continue to get lighter, stronger, and more aerodynamic. Recent concept frames constructed out of graphene have been making the rounds at trade shows. With high rigidity and a claimed weight of just 750 grams, these frames give us an idea of what bikes will be like in the future. The molecular structure is 300 times stronger than steel, making it one of the strongest building materials in the world. While graphene may appear to be an obvious next step for bicycles, this material still has a way to go before mass production can be figured out, and before the price becomes economically feasible.

Given all the recent advancements with carbon and other composites, it may seem like steel and aluminum frames will soon be a thing of the past. But there’s many riders and manufacturers who still prefer the ride of a good old-fashioned metal bike. While steel and aluminum are technically weaker than carbon fiber, their capacity for catastrophic failure is also less. Unlike carbon, when metal is dented, scratched, or blemished, it doesn’t really lose any of its integrity. This makes riders more confident in the durability of their bikes, which goes a long way when they’re considering a purchase.

Bikes have come a long way from wooden frames and iron wheels, and it’s entirely possible that the “modern” bikes of today will one day appear laughably underdeveloped. But that’s one thing that makes bikes special too. They’re an odd blend of centuries-old concepts and contemporary technology. While it’s fascinating to see the way bikes evolve and develop, it’s also ok to hope they don’t change too much. After all, their simple, analog design is one of the key reasons so many of us all over the world love to ride them.

By Jeff Walker, Content Writer,

Shifting Trends is our latest blog series covering recent changes and developments in the bicycle industry. This is the third in the five-part series. Click here to read our last post, and check back next month for our next installment.