The way a bicycle moves forward is its rider put Watts into the bottom bracket axle. Fundementally, the Watts equation contains ‘Aerodynamics, tyre deformation, geartrain losses and “Sin theta for the inclination’. Knock off most of the Aerodynamic factor and add on more ‘Sin theta’ value for the gradient.
Fit the bike with gearing so the rider can pump 300 watts into the BB when riding up a 8% grade at 8 mph, and he’s happy. On my racebike, it’s a 45” gear, or 39 x 23.
On an 8% grade, I shift down to 46” on my TT bike and keep whacking out 75 – 80 rpm in the usual TT tucked position. Speed is lower than on the flat. Feeling is the same. See Sheldon Brown’s views on gearing and hills.
