Sunday, October 17, 2010

Light bikes: cranksets

A bicycle could be described as an economical means of transportation and sport, not because it’s cheap—it isn’t—but because it’s condensed to its basic components. It would be impossible to take one of them out without changing the nature of the entire machine. Without wheels, a bicycle wouldn’t be a bicycle. Handlebar? No, without the handlebar, we might as well lock the front wheel and go straight to…where? What about pedals? Crankset? Same thing. Saddle? In theory, we could do without a saddle, but it’d be inefficient and kind of uncomfortable, at least to my way of thinking.
Only a few years old, the SRAM Red group of components is one of the
most reliable and problem free. Its crankset, shown above, is not one of the lightest.
The latest, 2010 version for a BB30, however, is. Very much worth considering, 
if your frame can accommodate a BB30.
Of all these components, cranksets are especially susceptible to experimentation and upgrading, to take advantage of new materials and methods of construction. There are many choices available, responding to different sets of priorities. What are the criteria of choice? They are mainly two, one is stiffness, perhaps the more important, and the other is lightness.
It’s obvious that the crankset should be stiff; all of its smaller parts, from the bottom bracket to the cranks, should be working as one. When they don’t, because there is some slack, or because one of them bends just a little under the thrust of acceleration or the push of a climb, some of the energy conveyed by the legs gets lost on its way to the chain. It is also important that the crankset be as light as possible, as it contributes to the overall lightness of the bike; we all know how important it is for a bike to be light, don’t we? But, stiff and light at the same time? 
A couple of years ago, Shimano produced a version of their DuraAce crankset made of a
combination of aluminum and carbon. In a typical Shimano fashion, it received a very
uninspired name, FC-7800C. The cranks consisted of an aluminum core wrapped by a layer
of carbon. The chainrings are also made of aluminum and are milled exquisetely. Compared to
their production model, the weight saving was minimal. Overall the sculptural quality
of this crankset is undeniable: this is a beautiful component.
No compromise is needed. In recent years, the tendency of bicycle components has been to employ the lightest possible materials, accompanied by construction techniques that maintain the desired stiffness, without falling apart at the least suitable moment.

The eeCrank, by eeCycleWorks. This is an early prototype of their upcoming crankset.
It is very light and exceptionally strong. One can see the designer's mind at work,
extracting all material that is not strictly necessary to its performance.
Photo: ©

One of the most recent products, the eeCrank, by the same designer who makes the eeBrakes, about which I wrote so enthusiastically a couple of weeks ago, is on the verge of unveiling his latest prototype. According to one reviewer, it provides the best balance of lightness and stiffness. Craig Edwards, the designer and mastermind at eecycle Works, its manufacturer, challenges the general trend, that of using carbon everywhere, in favor of aluminum alloy. When in production and available to customers, sometime in 2011, that’s the crankset I would be seriously interested in setting up on my own bike.

The major manufacturers of bicycle components, Shimano, SRAM, and Campagnolo, all offer excellent products of this kind.  They perform flawlessly, shift smoothly, are designed to last longer than the bicycle frame, look good, and are stiffer than a telephone pole, but they have a fatal flaw in common, in my opinion: they are not the lightest of their species.
The Zipp VumaQuad crankset: very well made and good looking. To save weight, its
designers have reduced the spider's legs to four, rather than the traditional five.
I am looking for that magic balance between weight, performance, and looks that makes my heart sing. I think I’ve found it for my bike: the Zipp VumaQuad crankset is light and stiff. I like the way it shifts. It’s not perfect, I know that, but with time and miles, I’ve learned to live with its quirks. For example, to save weight, its designers have made it impossible to use anything but their own chainrings—they are not the cheapest available. I’m not crazy about the graphics, either. 

The Clavicula crankset: I'm not sure how far the designer has pushed the analogy
with the human bones. One can, however, easily visualize the distribution of forces
from its design. Photo: ©THM Carbones.
Of course, there are lighter cranksets available. Some of them are made by German companies, which have a talent for taking carbon-fiber manufacture to the extreme. Perhaps one of the lightest available is the Clavicula, made by THM Carbones. Another one, also made in Germany, is the Morpheus, made by Ax Lightness. Naturally, Storck bicycles also belongs in this group, with their own PowerArms. 

The chainrings themselves contribute to the crankset overall weight. It’s probably a good idea to read the fine print in the manufacturers’ descriptions to see if the chainrings are included in their measurements or not. There isn’t a great deal of variation in the weight of chainrings. There are, however some that are entirely made of carbon fiber. They are very light. Are they road worthy? Honestly, I’ve never tested them, but I have received conflicting reports about their reliability.
I am sure it’s possible to find cranksets that are even lighter than the ones mentioned above—by a few grams. These grams come with a large price tag. It’s all a question of priorities.   

No comments:

Post a Comment