I'm just shocked, SHOCKED at what Todd wrote. It seems most unseemly to use common sense and empirical data... Along those lines, Jim Papadopoulos did some analysis showing that the difference in vertical compliance between radial-spoked and 4-cross was less than the difference a stroke or two of the pump would make. Among well-built wheels, the flex was concentrated in the tire.
Harvey "appreciate my bikes without trying to overanalyze it" Sachs mcLean va
Todd wrote: I've seen some other posts recently regarding tubing and ride quality, and I thought that I would jump in here with a couple of comments. First, a bicycle frame is pretty darn stiff in terms of vertical compliance regardless of what tubing is used. Flex in the tires, saddle, seatpost, stem, and handlebars will be many times that of the frame. I have not seen much testing on this other than the Bicycle Guide test involving 7 Mondonico frames built with different Columbus tubes. The testers in that case couldn't tell the difference between plain straight gauge tubes and EL-OS.
Second, all the various steel alloys are virtually identical when it comes to stiffness. So, an 853 frame should feel identical to a 531 frame if the tube diameters and wall thicknesses are the same. However, they rarely are. The benefit of a high-strength steel like 853 is that you can build with a thinner wall and still have sufficient strength. A frame with thinner-walled tubes will more flexible.
When it comes to frame flex, what is noticed typically is lateral or torsional flex, both of which I consider to be quite undesirable. So, what constitutes a comfortable riding frame? I think it basically comes down to wheelbase and the fork. A long wheelbase bicycle (or car for that matter) will be perceived as having a smoother ride. The fork, since it is cantilevered off of the frame can flex quite a bit. I believe that the harsh ride reported of fat-tube aluminum bikes is really caused by the overly stiff unicrown forks and extremely short wheelbases that became fasionable at the time, not from the frame.
I have heard some of the framebuilders here talk about using thinner seatstays and such to get a better ride, but I haven't seen any evidence that this is true. Is this just more bicycle myth and lore that has been passed down?
Todd Kuzma Heron Bicycles LaSalle, IL 815-223-1776 http://www.heronbicycles.com
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