Typically, we have four different materials that we look to when producing bike frames. Aluminium is a versatile option, striking a great balance between price point and weight. There is steel that also promotes great versatility, and the advanced modern steel alloys we see today can make for very lightweight frames with beautiful ride quality, while at the same time being super durable and also repairable. Titanium takes metallic frame materials a step further and has a strength to weight ratio that surpasses both steel and aluminium. Its corrosion resistance is another reason it is such a great material for making bike frames, and is noted for its ‘springy’, comfortable ride feel. Carbon fibre is the choice for the rider who is looking for speed. The lightest frames on the market today are made from carbon fibre, and the manufacturing process associated with making carbon frames allows engineers to make use of more aerodynamic frame profiles. But why would we choose one material over another? Are some materials better suited to certain disciplines? Let’s dive in and examine what can be offered by these different materials.
Beginning with aluminium, we might view this material as quite a modern material for bike frames. In actual fact, its use can be traced as far back as the late 1800s. Surprisingly, a brand known as 'Lu-mi-num' made a frame using a monocoque-type construction technique, producing a very striking looking and lightweight frame for its time. But fast forward to the late 1970s, and we begin to see the first mass-produced bike frames being made by Vitus, paving the way for the material in the modern age.
Aluminium makes a lighter weight frame than steel due to its lower density, but with this characteristic comes less strength and also more flexibility. To avoid premature failure, aluminium bike frames need to be made using larger diameter tubing to achieve the stiffness required to prevent it flexing too much. However, we can still make a lightweight aluminium frame because the wall thickness of wider tubes can still be very thin. To demonstrate this, we can take two tubes of the same wall thickness and increase the diameter of one, the wider diameter tube will be stiffer without having to increase its wall thickness. It is this property that allows us to build a frame that is lighter weight than many steel frames – we can build a strong enough frame using just enough of a lighter weight material. We can also decide to use hydroformed tubing to give profiles that are refined into certain shapes to allow for better control of both directional flexing and stiffness, therefore allowing a tube to flex more in one axis, and less in another. But even with hydroformed tubing, the ride quality of an aluminium frame can often feel stiffer than other material choices. The advantages here are that we can build a very responsive frame suited to specific disciplines. Where a cyclist rides predominantly on smooth surfaces, for example on a velodrome track or on a closed criterium track, an aluminium frame may be the best choice. It will be stiff enough to allow for optimal power transfer. The durable nature of aluminium also means that its robustness will soak up punishment from crashes (crit racing is renowned for crashes being common). The generally cheaper price of aluminium race frames when compared to carbon fibre means that the rider may be more inclined to choose an aluminium frame for this discipline, taking into account carbon’s failure characteristics, which are often catastrophic. Its failure characteristics dictate that a crashed carbon frame should be thoroughly checked for cracks and other damage, and may mean there is a higher likelihood of the frame needing to be written off after a crash. For this reason, a criterium racer may lean more towards an aluminium frame and its ability to absorb more impacts before it fails.
But aluminium may also be the material of choice for other types of bikes; the budget conscious adventure rider still has a range of very capable bikes to choose from. With tough but lightweight, hydroformed tubing, and enough space for wider tyres to allow for a comfortable ride, aluminium frames can be a great choice for off-road riding. And when we combine components such as suspension forks with wider tyres, we can achieve a super compliant ride with great off-road capability. The stiffer nature of an aluminium frame plays a harmonious part when paired with these component choices – responsive, lightweight ride feel for tackling technical terrain, paired with the forgiving comfort that comes with the larger volume tyres and suspension components.
Alternatively, an urban commuter might want something that is light enough to perform when the clock is ticking on their way to work, but they may be reluctant to splash big money on a bike that will be subjected to a lot of rough use. Choosing an aluminium framed hybrid as their workhorse will tick the boxes.
Aluminium is a great material for bike frames. Its structural benefits are numerous and because of its lower price point, it can make cycling more accessible. However, it is not the perfect choice for absolutely every kind of bike, and unless the manufacturer is adequately equipped for aluminium specific manufacturing processes, making a frame is not quite as simple as welding a few tubes together. The heat-treating stage of making an aluminium frame can complicate matters, and being able to control this stage accurately can be costly both in machinery and energy, although, some aluminium alloys lend themselves better to simpler methods of heat treatment. But for this reason, it is far less common to find custom bicycle framebuilders using aluminium as their material of choice, so realising a made-to-measure aluminium frame may be more complicated than specifying steel, or even titanium. And when we consider the environment, we must remember that the process of TIG welding is also somewhat energy-thirsty when compared to other materials’ fabrication practices. Another aspect to consider is aluminium’s lack of fatigue limit, which means that the repeated small level stresses associated with the prolonged use of a bicycle will result in the material’s eventual failure. This is a reason why aluminium bike frames can be built to a relatively low weight, but only to a certain limit in order to include enough material to stave off fatigue failure. When we do consider the end of an aluminium frame’s life, we can also think about where it might end up after it is discarded. Currently, aluminium is widely recycled, so we can rest easy knowing that the material used to make it could find itself into a new product.
If we want a bike frame to last us a lifetime, that can even be passed onto the next generation, a frame that can be easily repaired or even modified, then we need look no further than steel as our material of choice. For well over one hundred years, steel has been the staple for making bike frames, and as the material has evolved into stronger alloys with corrosion resistant properties, tubing is able to be drawn with finer wall thicknesses, resulting in lighter weight frames with superb comfort.
The longevity of steel bike frames is something that cannot be argued with –there are steel bikes that exceed one hundred years in age that are still being ridden at events such as L’Eroica. This practical and time-resistant material is here to stay, and even as manufacturers explore the use of new materials, steel still remains irreplaceable. It may no longer be the number one choice for the race machines of the professional peloton, but the dependable nature of steel makes it the number one choice for the cyclist who wants to tackle the far-flung roads and trails of the world. For the adventure cyclist covering great distances over remote topography for months at a time, steel has proved itself time and time again. This is testament to its versatility, and it has been shown to be repairable using some very basic techniques. In the early days of the Tour de France, necessary frame repairs were carried out en-route at blacksmiths’ forges. Even in the 21st century, it has not been unknown for long distance cycle tourists to have their steel bike frames repaired by truck mechanics, wielding MIG welders, and to great effect! This says a lot about the ease of workability that comes with steel when compared to other metals, and for this reason, it lends itself well to custom frame fabrication. The scope of possibilities is incredibly broad when it comes to building steel frames. It can almost be seen as a medium of artistic sculpture, and some of the designs that are being produced by custom framebuilders are works of art in themselves. The range of shapes and geometries achievable by joining steel tubes together seem almost endless. And not only is a fabricator limited to building a steel frame from scratch, but existing bikes can be modified and transformed. Back in 2022 in our House Blend series, we documented the transformation of a steel Bombtrack Beyond frame into a tall bike at the Dropbar Bikes workshop, with Harald Kinzel. This was a first-hand demonstration of what can be done with steel, and really highlighted its reusable, recyclable nature. We highly recommend checking out the video, it serves as a great five-minute insight!
Apart from being the embodiment of utilitarianism, building a fast, lightweight, but also comfortable steel bike, is easily achieved. The newest steel alloys in production allow for ever finer tube butting, and the tough nature of stainless steel allows butting profiles to be pushed further, helping manufacturers to produce even lighter weight tubing. The last bike frame of steel construction to be spotted in the pro peloton was in 2019, proving that the material was still race relevant. Granted, there were carbon frames of lighter weight available at the time, but there is no denying that the frame being ridden here turned heads.
The beauty of a steel frame may not just be skin deep, however. The noble source from where the material comes from in today’s world of bike frames also perks the attention of the environmentally conscious cyclist. A lot of steel that is used in bicycle frame tubing production comes from recycled material. Companies such as Reynolds Technology, the legendary British tubing manufacturer to who we owe the invention of the butted tube, use 100% recycled steel to make their tubes. Also, the metal waste generated by many frame and frame component manufacturers is also recycled. For example, the excess steel produced during the investment casting of lugs and dropouts often finds its way back into the factory process, and eventually into other areas of industry – a Taiwanese company called CWIDE uses a precision lost wax investment casting technique in their manufacturing, and the waste steel product from this process is used to make heavier duty products such as manhole covers and excavator buckets. And as the years tick on, even this ancient material is finding its way into more modern methods of manufacture. Steel is able to be 3D printed, which creates far less waste than investment casting. In the modern age, this manufacturing technique is becoming more widespread in the manufacturing of frame components. The archaic but nonetheless very effective and efficient method of tube joining known as brazing, is also still widely used in bicycle frame manufacture. It is worth noting that brazing does not use very much energy at all—the rate of fuel consumption requiredto braze up a bike frame is considerably less thanthat of many cars as they are driven day to day.
One feature of steel, and perhaps its most significant attribute, is the way it rides. The way it absorbs road and trail vibration is notable, and manufacturers often attempt to emulate this characteristic when making frames from other materials. The forgiving nature of steel, is touted as ‘springy’ and ‘lively’, making for a very smooth ride. Steel is loved by so many cyclists because of this ride quality that is so unique and original. For so many years, steel was the only real choice for making bike frames, and perhaps this ride quality explains one of the reasons as to why other materials were not so actively pursued until relatively recently. You will hear people use the phrase ‘steel is real’ when talking about bike frames, and for a very long time this was true, and is indeed still true today for many reasons. A steel frame is a joy to ride, and when the cyclist wants first and foremost to enjoy cycling, then steel with its great ride quality may be the perfect answer.
But what if we want to pursue all out speed, with no compromise on drag and stiffness, giving unadulterated race performance? Sometimes we need the edge over opponents, and when time is measured in microseconds, every watt counts. When designing for carbon fibre manufacture, the frame shapes that are achievable are different beasts altogether when compared to what we see when working with metal. Typically, a production carbon bike frame is made by laying up carbon sheets into a CNC machined mould, allowing the frame components to be constructed and joined to one another in a seamless way. Here, the engineer can achieve monocoque shapes that address three key areas of race bike frame production – stiffness, weight, and aerodynamics – with a much more refined insight and scope of adjustment. More carbon can be laid up where stiffness is more important, and where weight can be saved, the layup can be made to be thinner. With this kind of design, engineers are not limited to prescribed tubing standards or joining techniques. State of the art Finite Element Analysis (FEA)and Computational Fluid Dynamics (CFD)software helps to simulate frame testing before any of the physical production happens. This facilitates the pursuit of bolder designs, without the high cost of creating numerous physical prototypes – the CNC moulds are very expensive to produce. A frame designer can also look at other materials when working with carbon fibre, and choose to emulate their ride qualities through means of different layup techniques. The forgiving ride that comes with steel and titanium can be channeled by focusing on different seat tube and seat stay shapes and layups. Conversely, the stiff, responsive nature of aluminium can be the inspiration when deciding on how much material to add to the bottom bracket junction. Having the capacity to make use of the 3D design space offered by CAD programs gives the engineer virtually limitless space to develop complex shapes that address the requirements made in the frame’s design brief. This method of design process isn’t just unique to carbon fibre manufacture however, but it is quite essential to allowing the engineer to get the best from the material and emphasises its place as the most modern material in our lineup.
Having said this, designing a frame in carbon to emulate the ride qualities of other materials can end up being quite a challenge. Because the material is still relatively in its infancy compared to other metals, such as steel, which has been around for thousands of years, some teething problems are inevitable. Occasionally, carbon bicycle frame manufacture can throw up quite unexpected issues. Two to three years down the line after manufacture, some brands have encountered failures in batches of frames made using very fine layups and tube profiles. In areas where the material has been designed to flex to give a suspension effect or to aid a frame’s ride quality, careful consideration of the carbon layup is vital in order to avoid micro-cracks developing, which can ultimately lead to the catastrophic failure of a frame. Because of this, there becomes a point where the engineer may find themselves overcompensating by adding such an amount of material to prevent this failure, that the weight saving advantages from carbon fibre are somewhat negated. Striking this very fine balance is not easy and is a result of a lot of work and the associated trial and error that is part and parcel of the process. The fact that we are arguably still relatively early in the life of carbon fibre use as a bike frame material means that the potential for further positive developments is particularly exciting. Perhaps in the future of carbon fibre composites we will see much more resilient and flexible components, together with improved systems encompassing the whole concept of a material that better supports its own recycling. Currently, there are only a few products available made from recycled carbon fibre, probably a consequence of the fact that the process of carbon fibre recycling is itself also in its infancy. But as the material becomes more widespread, so does the community around it, and nowadays it is really not difficult to find someone who is suitably equipped and sufficiently skilled to repair a damaged carbon frame.
Like all materials, carbon fibre isn’t the absolute wonder solution to the manufacturing requirements of every type of bicycle frame. Producing custom sized carbon frames can be done, but the process may become prohibitively expensive if the maker is fabricating using monocoque moulds. Cheaper methods can be employed with the use of pre-made carbon tubing joined into pre-made clusters, but this sacrifices some of the benefits that come with monocoque construction.
As mentioned earlier, carbon’s different properties when it comes to impact resistance may be taken into account too – other materials may be a better choice when the bike’s intended use is of a more rugged nature, such as bikepacking or freestyle BMX.
But what if we are looking for something with a truly robust nature? A frame that won’t succumb to corrosion, with a ride-feel like nothing else. A frame whose weight is even lower than the finest stainless steel frames out there. Of course, we look to titanium. The futuristic aura that surrounds this exotic metal brings to mind visions of spacecraft and sound barrier-breaking fighter jets. However, with the first documented titanium bike frame being produced in 1950s Britain, we can see that the potential for its use in the bike world was discovered quickly – titanium was adopted as a manufacturing material only after the Second World War. However, it wasn’t until the 1970s that titanium really started to take off as a viable material for bike frames, and from there, the material was refined into something that was both comfortable and stiff enough to perform well.
These days, titanium bike frames are quite commonplace, but they still hold onto their reputation as the exotic, space age material with the material’s unique almost indestructible qualities. Frame manufacturers like to show off the material when they make a frame, usually leaving it in a raw, unpainted finish which never fails to turn heads. Today, the material can be used in both mass production and smaller level custom framebuilding operations. The TIG welding methods used to join the tubes are similar to those employed during the fabrication of steel frames, so the transferring of skills from steel fabrication to titanium fabrication is realistic.
The fatigue limit of titanium is somewhat greater than steel, therefore allowing the manufacturer to produce a frame with a much higher strength to weight ratio than steel. The frame can be made to be just as robust, but lighter weight than the equivalent steel frame. However, for reasons similar to those that we are confronted with when working with aluminium, we cannot make a titanium bike frame to be absolutely featherweight without noticing some shortcomings. Titanium might not run as much of a risk of failure when compared to aluminium, but if the tubes are drawn to wall thicknesses too thin, the amount of flex will become too great and therefore make for an ill-riding frame. Titanium is less dense than steel, so this naturally makes it a more flexible metal. This is why we don’t really see titanium frames on the market that are built with tubes as slim as what we see on steel frames. As mentioned earlier, a larger diameter tube is stiffer, regardless of its wall thickness, and the cost to experiment with larger, non-standard tubing diameters increases the bike’s end value. Sometimes, we do see titanium frames with hydroformed tubing, for the same reasons we see them being used on aluminium frames— this can help with refining the ride quality of the end result. But, you will have noticed the generally higher cost of titanium bike frames, and a lot of this comes down to the material cost. From some suppliers, a titanium tube can be around ten times the price of a chromoly steel tube of similar spec, and this is before we factor in the extra costs for the higher level of workmanship required to turn the tubes into a top performing bike frame. This being said, the extra cost that comes with a titanium bike frame can seem very much worthwhile, because in the end, we have a very lightweight, supremely comfortable frame, that will not corrode over time, and will absorb punishment from rough use, like the Terminator brushes off a shotgun round. But don’t worry, a titanium bike frame can still be defeated, just like the Terminator can be, and the material is 100% recyclable.
So what do you look for in a bike frame? The cost-effective functionality and performance that comes with aluminium? Perhaps in today’s age, the robust, repairable, and age-old reliable nature of steel is the most sensible option. Maybe you are chasing the clock and need nothing but the lightest weight, that can only be delivered by a carbon fibre frame with refined frame components and design techniques. Maybe it’s a forever bike that you’re looking for, and titanium’s mythical status is promising to you that in 200 years time your bike will still be going strong!
SEIDO ComponentsNovember 2025By Peter Skelton
