Gravel Frames: Alluminium and Steel compared

Steel or Aluminium Gravel frame? Which one is better?
There is not a definite response. Depends… The choice is played over two halves:

- technical-structural qualities of the two materials
- feedback that the rider wants from the bike.

Historically, we can see that it all began with steel. Girardengo and Binda the original “campionissimi” of Italian cycling both raced on a steel bikes, as did Coppi,Bartali and “the Lion of Flanders”, Fiorenzo Magni. Steel was used until the early 70's when we started to see the appearance of the first aluminum alloy frames. By halfway through the 90's, steel frames  were completely replaced by aluminium. However, less than a decade later, carbon fibre became the peloton's material of choice.

Let’s take a look at the pro’s and con’s of these two materials when applied to gravel frames.

Alluminium

Aluminium is a material that has a lower kg / m³ density than steel with a specific weight at a temperature of 20°C which is approximately three times lower than steel. For this reason it is no mere coincidence that the reduced weight was one of the main qualities that led brands to proceed further with development of aluminium for use in the cycling world. They were then able to combine reduced weight with the stiffness, not so much because aluminum is more rigid in an pure sense than steel, but mainly, due to the less complex manufacturing process of the tubes that gave the possibility to create different tube cross sections and profiles. It was found that an oversized tube, for example, guaranteed better responses when applied in certain areas to a frame.

On the other hand, an aluminum gravel frame has less ability to absorb and dissipate vibrations than a steel gravel frame. In more simple terms, precisely for this reason, it is said that aluminum is a "deaf" material. You can get around this obstacle by using, for example, wider flanges. Another critical aspect concerns the life cycle of the material which, when subjected to load and repeated stress cycles, undergoes yielding which leads to the deterioration of the structural qualities, up to the irreversible (although minimal) deformation of the structure.

Gravel frame in aluminium: Pro’s

• inexpensive
• Stiffness to Weight Ratio
• Low density

Gravel frame in aluminium: Con’s

• Rigid
• Over time less capable to resist stress factors
• Difficult to repair

Aluminium Gravel frame. Ideal for…

All of us who intend to ride to keep fit and who need a light inexpensive do it all, multipurpose bicycle.

Steel

More forgiving, comfortable and resilient than aluminum. The merits of steel have re-emerged in the last few years thanks to new manufacturing processes on gravel frames that have really pushed the level of workmanship to an extremely high level. Up until recently a steel gravel frame was considered a market niche and dedicated to vintage bike lovers. We can also consider that the specific chromium-molybdenum steel (Chromoly steel) structure is very similar to aluminium in terms of weight.
Another advantage of steel is the relative ease in which it can be worked. This consequently means that repair work can be carried out, obviously with a minimum of tooling and knowledge, more easily than aluminium. It is not a  coincidence that several gravel bikes destined for adventure and bike-packing excursions are offered with steel frames: the possibility of welding different threaded inserts to the tubes for attaching bags and accessories with a heavy loading weight are qualities that cannot be overlooked. This is why all manufacturers (from large companies to back shed craftsmen) offer steel gravel frames.

Aluminium Gravel frame v. Steel: Pro’s

• Guaranteed for life
• More forgiving and comfortable than aluminium
• Easier to repair and work on

Aluminium Gravel frame v. Steel: Con’s

• Weight
• More susceptible to corrosion
• Price
• Less machinability of the material (the ideal shape for welding is round tube)

Steel Gravel frame. Ideal for…

Adventure and bike-packing and to all those looking for comfort thanks to a bike that could last… forever.