FatandSlow wrote:
We seem to spend a lot of time worried about cross chaining and its corresponding friction losses here. While the concept makes sense, I wonder if it's a holdover from back in the day. Chains were wider, stiffer (laterally), and there was more space between cogs when we only had 5 cogs in the back on a 126mm hub vs. having 11 on a 130mm (rim brake) hub.There was more space between cogs, but due to the smaller cog count, the freewheels were still considerably narrower than modern 11-speed cassettes. The width of modern cassettes is the main reason that rear hub OLD switched from 126mm to 130mm, and despite the extra real estate provided by 130mm, modern rear wheels also need much steeper drive-side spokes at very high tension. The wider cassette actually results in cross-chaining experiencing far more extreme angles on current-gen drivetrains than on drivetrains circa 1980.
But yes, concerns regarding cross-chaining go way back. Many racers used to be extremely concerned about chain behavior in general... in retrospect it's hard to know how much of it was ever justified, and if so, when it was justified. Some of it definitely got pretty silly, like the efforts in the 30s and 40s to use derailleurs on racing bikes while keeping the amount of bends in the chain to a minimum (resulting in a variety of strange mechanisms that provided less than 10 teeth of chain wrap and didn't shift particularly well).
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I'd be at least mildly surprised to find that world-class time trialists spend much time in a 58x15 on a flat course. A look at a gear, cadence and speed chart shows when using a 58 big ring with a 23 tire, that for 34mph with a 15 cog, a cadence of 112 is necessary. For a 14 cog, the cadence is 105. For a 13, its 97-98 . For a 12, it's 90. For an 11, it's 82-83. Changing to a 25mm tire changes the required cadence to 111-112, 104, 97, 88-89, and 82. I don't believe we see cadence over 100 very often anymore, with the exception of descents. In his heyday, he-who-shall-not-be-named was in the 102-105 range. Tony Martin looks more like low 90s to me. Using 34mph and a cadence of 95, the rider is spending a lot of time in the 13. Not a big/small, but not likely to be a big/15, either.I think you'd have to accumulate some data to answer the question, because cadence choice varies a lot from cyclist to cyclist. Anyone could tell any narrative if they just picked a couple cyclists from any given era. Eddy Merckx and Bradley Wiggins set their hour records on very similar cadences to each other, for instance, both a bit over 100rpm.