Our bikes are made of chromium-molybdenum type steel, commonly known as Cromoly. It is a nobler steel than the low carbon steel, the latter the most used in the manufacture of bicycles.
To understand the benefits of Cromoly in relation to other materials, it is first necessary to understand some concepts:
Rigidity
Rigidity, in turn, is related to the elasticity of the frame when subjected to stress. The rigidity of a frame is given by the material used and by the design and engineering, which specifies the dimensions of the tubes and profiles used in construction.
Resistance
It is the ability of the frame to withstand external stresses without permanent deformation or total failure under stress. Chromoly frames have better impact resistance as they are able to absorb and distribute large amounts of energy without breaking.
Aluminium
Aluminum is the second most common material. It provides quite rigid frames, which is desirable when it comes to competitive performance. But that stiffness doesn't come from the material's properties (young's modulus). Because it is a less dense material, it requires a larger tube diameter and also a larger wall thickness. That's why aluminum bicycles can weigh as much as ordinary steel bicycles. They may be heavier than Chromoly bikes.
The vertical rigidity of an aluminium frame contributes to a harder ride, transmitting a higher spectrum of vibrations to the cyclist. This effect can be mitigated by using suspension. In road bikes, this effect can also be mitigated by the now common use of more flexible carbon fiber forks.
Not all steel is the same.
Steel is exceptionally durable and highly fatigue-resistant. More bikes are made of steel than any other material. It was the universal choice of racing bicycle frames until the emergence of aluminium in the 1970s and 1980s. And of course, the carbon fiber that appeared in the 1990s.
There are basically two distinct types of steel used in the bicycle industry:
Hi-Ten: This is a lower grade steel, usually 1020, commonly found in cheaper bikes. Especially those from department stores. It offers a good strength and weight ratio.
Cromoly: More sophisticated steel bikes will probably use Cromoly, or CroMo. Chromium alloy steel (0.8% to 1.1% ) and molybdenum steel (0.15% to 0.25%) to increase strength with an average carbon content of 0.28% to 0.33% . Also used in aeronautical applications and in the construction of vehicles for automotive competitions.
This material allows us to design lighter frames that consider a certain amount of flexibility using thinner-walled tubes. Tubes that go through a process called "butting" that essentially fine-tunes the center of the tubes to reduce weight, keeping the ends strong for the welding point.
This translates into a frame that can be as light as an aluminium frame and in what cyclists call a "live frame" or "stretch frame", and provides a smoother, more comfortable ride.
Chromoly is more resistant than aluminium, however, its density is a little higher (material weight), but because it is more resistant, it can be thinner and deliver a frame with less rigidity. And it is more reliable: with more predictable failure modes, deforming before breaking. Aluminium, on the other hand, is more susceptible to fatigue, and in this failure mode it behaves like glass, being able to break abruptally without showing much deformation.
Now that you have these concepts in mind, let's address the practicalities for choosing materials:
Comfort vs Performance
If you plan to compete, then an aluminium bike is the ideal choice for you. The lateral stiffness of the aluminum frames is highly appreciated in competitions, as they give a real sense of responsiveness, transferring the pedaling force more immediately.
On the other hand, if you intend to make daily use of the bike in transportation or tours, which require more time in the saddle, then comfort and durability are your priorities. Steel is the best option in this case.
Durability
All materials will tire with time, but some will tire faster than others. Ordinary steel can oxidize if not careful, but Cromoly, although also steel, can better withstand oxidation. Both materials are more durable than aluminium in the long run, as the latter is less resistant to fatigue.
So if you're looking for a performance bike designed for the urban environment, consider one of our Cromoly bikes. They are classic, light, durable, and provide a safe, efficient, and comfortable ride. Click here and check out
