A fully built-up “lightweight” road bike typically weighs between 6.5 kg and 7.5 kg. Perhaps unsurprisingly, this is not light enough for some recreational cyclists. Some people are obsessed with the weight of every part of their bike. Less is good. More is bad.
One way to make a given road bike frame lighter is to use carbon components instead of alloy. The catch is that carbon costs more than alloy. How much more? Read on.
I compared like with like as far as possible. For example, two components from the same manufacturer, where the only difference is that one is an alloy part and the other is a carbon part.
I started my Internet search with handlebars. Handlebars appear to be the component most often offered in alloy and carbon versions.
Stems were next. I was surprised at the large cost differentials between the alloy and carbon offerings from Zipp and Deda. Especially given the minimal weight saving of their carbon component over its alloy counterpart.
The Cost per Gram Saved for the Zipp and Deda carbon stems is so high that I excluded them from the average cost calculation.
I suspect that the availability of separate handlebars and stems will decrease as integrated cockpits become more commonly specified on new bicycles.
I looked at seat posts as well. Choosing a carbon seatpost over an alloy one is not just about the weight savings. Carbon seatposts are primarily chosen over alloy for superior vibration damping and increased compliance, making them more comfortable.
Nevertheless, weight savings also play a part in making a carbon seat post more desirable than an alloy seat post.
Group sets, i.e., combinations of crank arms, chainring, cassette, derailleurs, and brakes, are usually specified when a road bicycle is bought new. However, it is possible to swap alloy crank arms for carbon crank arms.
The list of comparable alloy and carbon crank arms is small, but the Cost per Gram Saved mirrors that of the components listed above.
Oversized Pulley Wheel systems are niche components that replace the stock pulley wheels and cage on rear derailleurs. They are primarily an aesthetic upgrade, though they do save a couple of watts.
Pulley cages are among the worst value upgrades per gram saved.
If you want to push the boat out, there are weight savings to be had in using carbon bottle cages rather than alloy bottle cages.
Interestingly, there are alloy bottle cages that are lighter than carbon bottle cages. The Average Cost per Gram Saved calculation below excludes the Supercaz vs ENVE comparison.
Alloy wheels can be upgraded to carbon wheels. I have left wheels out of this comparison because carbon wheels offer superior performance over alloy wheels through lighter weight, improved aerodynamics, and higher lateral stiffness, leading to faster acceleration, better climbing and better handling.
Carbon wheels are the most impactful upgrade because of this. Generally speaking, the benefit of carbon handlebars, carbon stems, etc., over their alloy counterparts is largely in weight savings.
The Average Cost per Gram Saved for all the carbon components listed above, save for the Zipp and Deda stems and the ENVE bottle cage, is USD2.97.
Remove the highest and lowest Average Cost per Gram components, the Pulley Cage and the Bottle Cage, which are probably the least purchased carbon components anyway, and the Average Cost per Gram Saved falls to USD2.83.
This is still a high cost. USD283 to save 100 grams. 100 grams is the weight of four AA batteries.
We read a lot in the cycling press about the weight saved by using carbon components. And many cycling enthusiasts happily spend the USD283 or so to reduce the weight of their road bike by the equivalent of a standard McDonald’s hamburger.
We read far less about the fact that when the weight of the recreational cyclist and their road bicycle is taken together, the road bike contributes less than 10% of the total.
I weigh 82 kg on a good day. My road bicycle weighs 7.5 kg. The total weight is 89.5 kg. The split in weight distribution is 91.62% (myself) to 8.38% (my bicycle).
The opportunity for weight reduction is clearly on my side of the equation. Losing 1.22% of my body weight is equivalent to spending USD2,830 to lighten my bicycle by 1 kg.
I know where I would rather put in the effort.
Old Roots, New Routes 