Comparison frame material
To assess our learnings from the interviews, we researched and compared frame material. Here's an overview.
As nicely phrased in the book Circular Cycling by Erik Bronsvoort and Matthijs Gerrits, to "own a bike is to own a platform". Therefore, one of our biggest questions since we started was to know which material was best suited to create a longlife bike. We researched different options: bamboo, stainless steel, aluminium and regular steel.
Initial research had shown the high potential of bamboo for various reasons:
However, bamboo turns to be a rather marginal product when it comes to producing bicycle frames for two main reasons:
- The raw material is unavailable in scalable quantitiesThere's currently a very limited amount of dry bamboo sold locally. Why? Belgium isn't exactly an exotic place (that's the least we can say!). Bamboo could be dried by machines but, 1. the energy needed would be huge and 2. the strength of the bamboo would be negatively impacted. Raw material - if used in large scales - would then have to be imported from Asia.
- Manufacturing processes are not easily standardizable, thus generating high labor costMost bamboo projets are currently operated by passionate frame builders as side projects. They learned by themselves how to source the raw material, how to design the frame and how to build it. As there's currently no standardized processes to scale a qualitative production of bamboo bicycles, it means that each bike can take up to 5 days to be built. Although the raw material is initially sustainable and rather low cost, bamboo bicycles end up being sold as expensive goods due to the labor cost involved.
Stainless steel is a material resistent to rusting and beautiful by design - which means there's no need to paint the frame and use the associated toxic component. Different project have been using it for its qualitative and sustainable properties, such as The Imagine Project (UK) or Bjorn Bikes (Canada). However, stainless stell isn't ideal for two main reasons:
- The raw material is very costlyTubes made of stainless steel are very expensive (4 to 5 times the price of regular steel).
- The welding process is more complexThe technique to weld stainless steel isn't identical to welding regular steel. There's less know-how, which means that if your bicycle breaks, you can't easily find someone to repair it.
Although stainless steel is nice on paper, it isn't realistic in reality. If well maintained, regular steel has already fantastic properties and last an extended amount of time.
We spent a limited amount of time researching aluminium and carbon as these materials aren't ideal for our target group of daily and touring cyclists. However, we were interested to find out the energy needed to create each material and its recyclable properties. For instace, the below data covers the amount of energy needed per kg of the production of the raw material (not the bicycle frame).
- Aluminium: 63 to 95kWh (but low kWh when recycled)
- Carbon: 51 to 79kWh
Note that many other measurements can be used to assess the environment impact of a material, such as fresh water waste, global warming potential and solid waste.
Steel is undeniably a material benefiting a high cost/quality/sustainability ratio.
- Longlife BikeDuring the interviews we organized, a bike mechanic told us: "Steel & longlife frames used to be normal. My father is still riding his old bike." It speaks for itself, right?
- SustainabilityThe amount of energy needed per kg of production (raw material) is fairly limited, going from 6 to 14kWh if new and 2 to 4kWh when recycled.
- CostA set of tubes from Reynolds (UK) or Colombus (IT) is affordable.
- Know-howSteel is the most common material worked by bike makers, making it easier to produce the frame and repair it if needed.