Originally Posted by
Trakhak
Curious how people are now obsessed with fitting the widest tires possible in their vintage steel bikes. Apparently not quite comfortable enough.
[heh, heh, good zinger. Steel is real when it suits us, but rubber rocks when the going gets tough.]
As Sheldon Brown wisely said, in response to a question on the topic of frame material and comfort,
"A bicycle frame is made up of triangles, and there is no compressibility in the frame members whatever they're made of. You've fallen for folklore. . . . Ride comfort is much more affected by geometry, saddle type, and, even more important, tire choice/pressure.” . . .
This is not correct. An ideal triangle cannot shorten any side but this assumes the sides and joints cannot bend — if a line segment bends, the polygon is no longer a triangle as there are now four angles and sides or else one side becomes a curve. So this geometric precept involves some question-begging. Real triangles do deform under load and the degree to which they resist, spring back or even begin to vibrate in resonance depends on the factors Mr. Brown mentioned, but also the material, which he wants to debunk. Make a triangle out of solid copper wire with the joints soldered. If you push in one side ,the other two sides bend in to compensate. That would not make a vey good bicycle, or a bridge, or any other triangulated structure. The same mass of copper formed into hollow tubing would be stiffer but no stronger. Using steel, or polystyrene plastic for the triangles would give different properties again.
OK, this is
reductio ad absurdum but my point is the role of material in a bike frame (or a bridge or an orthopedic implant) cannot be dismissed just by saying triangles can’t deform, because they do. As the owner (but never racer beyond sprinting for road signs) of several high quality steel bikes I am prepared to admit the only reason to prefer them over newer materials is that they are much cheaper and fit at a sweeter spot on my personal marginal utility curve. And I have actually ridden one or two CF frames short distances. Impressed but not blown away, for the price.
And the risk of asplosion.