The downside for aluminium is that it can produce a slightly harsh ride quality - though some riders appreciate this. Though easy to dent, it's unlikely to fail completely - making it a good choice for road and criterium racers.
And there was a time - before the s - when it was simply the only option. Steel tubes, like aluminium, can be butted to create strength where it's needed and cut weight where possible. When it comes to joining the tubes, manufacturers can opt to braze or use lugs. The former is a lot like welding but uses an additional material, whilst using lugs means slotting the tubes into joins - there's a lot of room for artistry and creativity here.
There are two key families of steel frame - Hi-Tensile and Chromoly. The latter is an alloy form, and is much more durable than Hi-Ten which is cheaper. Steel might be real, but it's also heavy. However, it also has a notably springy ride quality, which enhances comfort over long miles.
Repair is easy too, and steel is very durable - though it is open to corrosion. All in, steel is often reserved for touring bikes, and winter bikes - any machine where the rider is keen to plod in comfort. Very much the material of the boutique custom frame builder, the best Titanium is lighter and stiffer than steel, with a a spring in its step - it's comfortable, light, stiff, and longer lasting than the other metals. When used to create a bike frame, Titanium is alloyed - often with aluminium.
Once the tubes have been created and formed, they're welded together - like aluminium, though the process is slightly more drawn out as the sections being welded can't be exposed to oxygen. Sound like the dream material? For many it is. But it's also expensive, if done right - so it's really the ideal material for that dream, custom bike you'll cherish forever.
Cycling Weekly's Tech Editor Michelle Arthurs-Brennan is a traditional journalist by trade, having begun her career working for a local newspaper before spending a few years at Evans Cycles, then combining the two with a career in cycling journalism.
When not typing or testing, Michelle is a road racer who also enjoys track riding and the occasional time trial, though dabbles in off-road riding too either on a mountain bike, or a 'gravel bike'. Adding material in highly stressed areas can also help redistribute stress to minimise the stresses experienced. Hydroforming is used with aluminium tubing to form complex shapes. As is more ductile, it is more likely to be formed this way. Fluid is run through at incredibly high pressure forming the tube to the shape of the mould it is in.
This allows the dimensions and geometry of the tubing to be tailored to provide certain ride characteristics and can also help redistribute stresses in the frame. Steel can also be shaped, though hydroforming for steel is not really applied to bicycle tubing. Instead tubes are modified mechanically. Ovalised tubes essentially act as a larger tube in one direction, and as a smaller tube at 90 degrees to this. This provides stiffness in one direction but compliance in the other.
Titanium has its provenance in the aerospace industry, where it is widely used. While as an element titanium is very abundant, it takes a lot of effort to refine and process into the tubing used for frames. It is relatively hard to work with, wearing out tooling more quickly and requiring a controlled atmosphere for welding.
All of this drives up its cost significantly. However titanium genuinely provides a frame for life. It is incredibly hard-wearing and corrosion resistant, which is also why it is often left unpainted. It can be made to have very high strengths. Less dense than steel but heavier than aluminium, it also falls roughly in the middle in terms of stiffness.
It is more difficult to find butted titanium tubing, though as its popularity increases manufacturers provide more and more options. CFRP has incredible strength and stiffness for its weight, allowing very lightweight frames to be built. Metals are isotropic, meaning their mechanical properties are the same in all directions. It resists loads in all directions.
On the other hand CFRPs are anisotropic. Their properties are dependent on the direction of load. Indeed on some frames it is possible to visibly squeeze the tube walls together. CFRP consists of microscopic carbon fibres aligned and held in a resin matrix. The fibres have diameters down to 5 micrometres, much thinner than a human hair. These are bundled together to form a tow. The fibres are like ropes, providing most of the strength. They can withstand tension, but would crumple if compressed.
The resin matrix ensures the correct alignment of the fibres, and provides additional compressive strength. The resin must be cured to set the shape of the composite. Most manufacturers now use pre-preg carbon; sheet of carbon fibres that are pre-impregnated with resin. These are usually uni-directional - the fibres are all aligned in one direction - giving high strength along the axis of the fibres.
The sheets must be built up in multiple layers - forming a laminate - placed at different angles to withstand different loading directions. The way this is done is know as the layup. Woven pre-preg may be used as an impact resistant top layer and to give a better surface finish. Pre-preg sheets are used to produce monocoque frames. The sheets are cut to shape and layered around a core. A frame may use hundreds of individual pieces.
This is then placed inside a mould and cured at high temperature and pressure. Originally used in the aerospace industry, it can have a high strength to weight ratio, but it is quite expensive. This is the ultimate frame material for unconventional frames and shapes, as it can be molded and tuned more than any metal. Metal Matrix is like carbon fiber, but it uses ceramic fibers and the metal aluminum acts like the epoxy. All metals used in bicycle frames are alloyed, or small amounts of other metals are added to give the metal different properties.
However, bike people usually refer to alloy as aluminum alloy. Forging and Working The strength of any type of alloy is not just a function of the alloying, but the also the heating, cooling and mechanical working rolling, forging, extruding, etc.
Depending how much a material is heated and how fast it is cooled, it might become harder and more rigid or brittle and soft. This is because the more you heat a metal, the more you change the alignment of the crystalline structure.
It is almost always better to use less heat and mechanically work the metal, like in cold forging. That means you can use thinner walled tubes, and thus design vertical flex into a bike.
Steel is also very durable, highly resistant to fatigue, and unlike carbon fiber and aluminum, can easily be repaired. The downside is that it can rust. As bike-packing and bike-touring grow in popularity, steel may make a comeback as a great material. Alloys are popular in frame-building as well. Chromoly—chromium-molybdenum—is another common frame material used on many lower-end department store bikes. Easton Sports introduced scandium as a cycling-friendly tubing material, and for a while, it was everywhere: Ridley, Redline, Rock Lobster and Kona all had scandium cyclocross frames in their lineup years ago.
Scandium is mixed with aluminum in order make it stronger, but fell out of favor after only a few years on the market. Rumors around its fall from grace include a marketing issue because it was not well-understood compared to aluminum, or a knockoff problem that resulted in a bad reputation after the poorly-welded cheap frames began to fall apart. Bikes and Gear. United States. Type keyword s to search. Today's Top Stories.
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