by Keith Couture
Bamboo, not just the preferred snack of Panda bears, has long been used to build structures, scaffolding, water transport systems, flooring material, kitchen utensils, boats, not to mention its use as a decoration, or even in cuisine alongside water chestnuts. It didn't take long for someone to conceive of a bicycle made from bamboo, too. The list of boasts about this wonder-material grows:
“Bamboo is lighter than aluminum!” Some say.
“Bamboo has a higher tensile strength than steel!” Claim others.
“It's sustainable to grow! And can also grow up to one meter a day!”
“It can be grown locally!” Another perk.
But, what really is the deal behind bamboo? Is it all it claims to be? I intend to dispel the myths, dissect the claims, and provide an objective analysis of this auspicious bicycle material.
A bicycle's weight is a major concern for a lot of consumers. In fact, for many it is the factor in deciding a bicycle's quality. Could bamboo really be the super-material that gives millions a race-weight bike at a fraction of the cost?
Bamboo is a porous, hollow material, which intrinsically cuts down on weight. The frame builder Calfee Design (http://calfeedesign.com/products/bamboo/) based out of California has bamboo frames that weigh anywhere between 1.8 kg to 2.6 kg (around 4 – 5.7 lbs.). Another frame builder called Cognitive Cycle Bamboo Bikes has frames from 2.4 to 2.6 kg also (about 5.3 – 5.7 pounds). A relatively new bamboo bike builder called Greenstar Bikes (http://greenstarbikes.com/) makes single speed bikes which weighs in at 22 lbs for the complete bicycle.
The Greenstar Eco-Force 1 weighs around 22 lbs
For comparison, an aluminum racing frame could weigh as little as 2.2 lbs (for an exceptionally light and expensive bike), more realistically around the 3 to 4 lb range, sometimes even including the fork. An aluminum bicycle from a department store, however, could weigh as much as 38 lbs, so material sometimes has nothing to do with it.
A steel bike can be made to be just as light or heavier, as well. A steel racing bike from the 80's for instance would probably weigh around the 19 lb mark for the complete bike, with a relative frame weight of roughly 4 lbs. Of course, a common chromoly steel bicycle, vintage or new, would likely come in at around 6 lbs for the frame, while the complete build could weigh anywhere between 24 and 30 lbs. A titanium bike or a carbon fiber bike... well, we're not even going to go there. Those materials can be used to build frames that are easily under 2 lbs. Of course there is some variety in the weight of them as well, it depends on the quality of the carbon fiber or titanium, and likewise for any material, be it steel, aluminum, or bamboo.
The point is, there is a great variety in bicycle weights for any material, and bamboo doesn't have a significant edge over any other. In fact, the standard deviations of each of these materials' weights are likely to be very similar. Furthermore, the components chosen for any given frame and what kind of a build is being done have a great deal of impact on frame weight as well (a single speed will likely be much lighter than a bike with thirty gears and big, knobby tires). So, is bamboo lighter than any other material? It's impossible to measure with all the variables out there. All the major materials are capable of creating bicycles of roughly equivalent weights.
Bicycle tubing strength has a lot to do with weight actually. If you're using an intrinsically stronger material you can shave more and more off of the inside of a bicycle frame's tubes, therefore lowering the weight. Some bamboo bike manufacturers boast that their bamboo has a higher tensile strength than steel. I was skeptical, so I really looked into material strengths. The wikipedia page on ultimate tensile strength was instrumental for this analysis.
Ultimate tensile strength is the maximum amount of force a material can withstand (in the case of tensile strength, stretching force) before breaking. Turns out there are a lot of different types of steel with a wide variety of ultimate tensile strengths. Bamboo has an ultimate tensile strength of around 350-500 Mpa (Mega Pascals, the unit used to calculate this type of force). It's possible after the bamboo has been treated with an epoxy or resin its tensile strength increases, but considering the ultimate tensile strength of epoxy adhesive is only 30 Mpa, I doubt it's that much stronger. To compare, structural ASTM A36 steel has an ultimate tensile strength of 400-550 Mpa. Ah-ha!
So, if some really strong bamboo at 500 Mpa went toe-to-toe with some of that steel that managed to top out at 400 Mpa, then yes, bamboo is stronger than steel. However, what are bicycles commonly made out of? These days, chromoly or perhaps during the peak of American and Japanese road bikes in the 80's a different mixture such as manganese-molybdenum. In either case, the UTS of these types of steel are between 700-900 Mpa, well over bamboo. Some steel bicycles are made from steel with strengths up to 2050 Mpa!
6061 Aluminum comes in at 325 Mpa, slightly under bamboo. Obviously aluminum is commonly used in bicycles, so these are strengths which make it perfectly safe to use as a frame material. Bamboo bicycle manufacturers are likely using the few exceptions when their material is stronger than steel to help market their product. Nothing wrong with that! It is vague enough to not be fiction.
One of the reasons bamboo has surged forward as a viable material to build bikes with is because of its suspected sustainability. Nowadays, stamp something with a sticker that says “sustainably harvested,” or “eco-friendly,” or “humanely produced” and it'll sell. Bamboo has those stickers written all over it. It has always been true that the mining industry is one that tends to exploit and abuse the laborers who produce the raw materials for metals (be they steel, aluminum, or otherwise). Some bamboo manufacturers tout the hardiness of bamboo and its ability to be grown in various climates, but the majority of this bamboo is nevertheless harvested from Thailand, Vietnam, and the rest of southeast Asia where it is abundant. There's nothing wrong with that of course. It's likely that the coal that goes into making steel for bikes comes from the same place, and the workers there are likely experiencing much worse conditions. Bamboo definitely seems to have the advantage in regard to the humanitarian aspect of production. What about the environmental impact?
A more traditional looking bamboo bicycle (photo by Flavio Deslandes)
Again, mining coal and other metals is terribly destructive to the planet. Growing bicycles sounds like the kind of idyllic fantasy that you'd come across after landing on a square in Candyland. However, if that bamboo is coming from across the ocean, there's the carbon footprint of that transportation to consider. Not to mention, bamboo does have to undergo a process of treatment which involves using epoxy to join tubes and lugs together (be they aluminum, hemp, steel, carbon fiber, or titanium). The majority of industrial epoxy is derived from petroleum. As a result, the process of making a bamboo bicycle still depends on mining and drilling. There are a growing number of epoxies that are plant based, however. Calfee Designs explains that they use hemp binding along with an eco-resin to construct their bikes, which seems like a step up. However, they also finish the frames off with a satin polyurethane, so there seems to be no escaping the use of petroleum products.
More generally speaking, I think the fact that bamboo bicycles are popular at all is an encouraging trend in and of itself. That we would look to this material for bikes suggests, to me, that we as consumers are becoming more aware of the commodity chain that links us to the people that make our things—bikes or otherwise. The more knowledge we have of how these wonderful machines are produced, the more connected we will be to the people that make them possible, and the more connected we are to those people, the more we have a stake in their well-being, which is extremely important if we want to keep the wheels of the world rolling.
For more info on a few different bamboo bicycle manufacturers check out: