>In fact, 753 typically makes some of the most flexible steel frames ever
>made. The fact that some people think they are stiff is evidence that
>most people can't reliably tell if a frame is stiff or flexible.
>
>Mark Bulgier
>Seattle WA USA
In testing bikes for Vintage Bicycle Quarterly, I found that an overly stiff frame (oversized, heavy-gauge steel tubing) and an overly flexible frame (a frame where an S&S coupler was not connected, so basically that frame had no down tube) feel very similar! Both were "dogs" that made climbing a chore. (I first rode the bike with the disconnected down tube in the dark, otherwise I might have detected the excessive flex by looking at the bottom bracket moving sideways.) So it is true that the sensations of an overly stiff and an overly flexible frame can be the same.
One has to keep in mind that asking riders about stiffness is asking the wrong question. To a rider, it really does not matter whether a frame is stiff or not. What matters is whether the frame is fast, whether it feels fast (giving you that psychological advantage), whether it is comfortable, or whether it has some other characteristic that matters to the rider.
Stiffness by itself is meaningless... unless it results in a characteristic that matters to the rider. And whether a stiff frame is faster or otherwise better or worse than a flexible one is open to debate.
However, even if riders cannot tell whether a frame is too stiff or too flexible, many _can_ tell when a frame has the "correct" amount of stiffness for them. It is interesting that most, if not all, racers in the 1970s and 1980s preferred lightweight, flexible frames over stiff and heavy ones - even for flat races where weight does not matter. To me and many others, a flexible steel frame feels faster and is easier to keep going at speed than a stiffer frame made from drainpipe. Because riders for generations have been concerned about frame stiffness and wasted energy, many erroneously concluded that the lighter-weight tubing was stiffer because it felt faster to them, and they thought the heavier drainpipe bikes were flexible because they felt slow. The opposite was the case, but as pointed out above, it did not matter, as racers really are concerned about speed, not stiffness.
The latest Vintage Bicycle Quarterly has a few articles on frame stiffness, energy loss (or lack thereof) and why some riders prefer flexible frames... -- Jan Heine Editor/Publisher Vintage Bicycle Quarterly c/o Il Vecchio Bicycles 140 Lakeside Ave, Ste. C Seattle WA 98122 http://www.vintagebicyclepress.com