Yesterday I recalled a conversation I had almost thirty years ago with Rory O'Rielly, former World Record holder for the Kilo and Team USA member for the 1984 Olympics. In addition to being a world class cyclist, Rory is a skilled carpenter. He was helping to build out Summerland Cycles, which I co-owned back in 1997. We were discussing rims. Hammering on a shelf, nails held between his lips, Rory uttered the following:
"All other things being equal, you can estimate the rigidity of a rim by how large a circle you can describe inside the cavity."
In 1997, such a pronouncement was prophesy -- a prayer for future rim design because nearly all quality rims were low profile box section, with double eyelets to beef up the rigidity. Seasoned builders remember rims such as Mavic's MA40 and MA2, along with similar designs from Ambrosio, Wolber and the like. The list of taller rims was very small; I can remember offerings fron Nisi, Saavedra and Araya -- I'm sure there were a few more. Rim profiles of that time were a response to road surface conditions and bicycle rim/frame material technology. Before the advent of carbon fiber bicycle rims, there were few wheels as comfortable as a low profile, 32 spoke box section rim laced in a three cross pattern. (Take a ride on H Plus Son's TB14 and you'll see what I mean).
Skip forward to the present day; Let's take Boyd Cycling's Altamont Lite rim as a good example of contemporary design. It looks like this:
The rim is part of my alloy, road stable which includes the Easton R90SL, Hed Belgium and Plus, Velocity Quill and Aileron, Pacenti Forza and H Plus Son Archetype. Compare it to the Mavic MA40: Weight? approximately 470 grams, (depending on drilling). Width? 20.3mm wide with an internal width of less than 14mm. From memory, the depth is around 13 or 14mm. Now, the numbers for the Altamont Lite. Weight is 450 grams on my scale; it is 24mm wide (19.8mm internal) and 25mm deep. It is 20 percent wider, almost TWICE as tall -- and stiffer to boot. All for the same weight, or less.
I would say that's progress.