Steel has its place but it’s not the wonder material some claim, says web editor Matthew Loveridge
I
love a good steel bike as much as the next tedious man in his thirties, but I don’t think steel deserves the almost mythical status it now enjoys.
If you want a bike to be as light and stiff as possible and you prize these characteristics above all others, make it out of carbon. The very lightest steel frames weigh more than very average carbon ones, and steel bikes that manage to be truly light only do so by virtue of using expensive high-end components.
Steel is also far less versatile than carbon composite. There’s no limit to the number of ways you can lay up sheets of carbon to target stiffness, strength and flexibility where you want it. You can also make pretty much any shape you want, a critical consideration when it comes to aerodynamics. By contrast, a steel frame is inherently more compromised. You can select specific grades of steel for different tubes and you can do some clever things to influence the material’s behaviour, but these methods all need to work within the limitations of the steel itself.
At the microscopic level, steel’s behaviour is determined by the crystalline arrangement called its grain structure. Manufacturing methods work with this to produce finished products with the desired characteristics. Think of it like wood – you wouldn’t make a table leg with the grain running crossways because it would be incredibly weak, with little ability to withstand shearing forces such as someone dragging the table across the floor.
Grain structure is one reason steel products are often bent, forged or drawn rather than simply machined from solid blocks. These processes preserve or refine grain structure and align it to the form of the finished piece, distributing stresses more evenly.
Machining, on the other hand, cuts through the grain structure. If you compare two outwardly similar metal components (eg, brake levers) where one is forged and one is machined, the forged one is likely to be stronger and less likely to have points of concentrated stress that lead to failure over time.
Many components are made using a combination of processes. For example, the overall shape might be produced by forging, but finer detailing added by CNC machining. For all of steel’s wonderful qualities, its fundamental structure can’t be changed at the point tubes are being turned into a bicycle. There’s only so far you can manipulate a tube.
Composites place more power in the hands of the manufacturer because the act of laying up carbon
