Originally Posted by
Trakhak
Your calculations are based on the assumption that
significant flexing of the fork does indeed occur. As I said, I'd love to see numbers from measurements.
Proponents of the idea that steel and titanium bike frames absorb road shock far better than aluminum frames make similar assumptions, but
measurements of 1997 model year steel, titanium, and aluminum race bike frames showed that, for the chosen simulated rider weight (not specified, annoyingly), the vertical compliance of a Lightspeed titanium frame was 0.064" (and that of a Serotta Ti frame with "oversize" main tubes measured 0.054") whereas that of a Cannondale aluminum frame was 0.049", a difference of 0.015". Is such a difference perceptible, apart from tire and seatpost compliance (and, of course, confirmation bias)? I think not.
(I originally wrote that straight forks now dominate the market, but then I realized I haven't paid much attention to current designs for years, so I hedged my bet.)
My formulas do not make any assumptions regarding the amount of flex, only that there is more flex with a shallower head angle, all else being equal. Are your measurements based on a frame only, or a frameset which includes a fork ? Bicycles frames are basically trusses, where most of the vertical load is carried axially by the frame members and there is very little bending flex. So, even the most flexible frame is going to have a quite rigid ride. If you really want a soft compliant ride, you’ll get a lot more benefit from larger tires inflated to lower pressures. The only time you are aware of a frame’s flexibility is when you apply power to the pedals, which results in torsion and out of plane flexure of the frame members (mostly the downtube).
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