Originally Posted by
63rickert
The bike does not climb. The rider climbs. The rider climbs with a bike. The bike is not an independent actor with some ability to climb. The bike is an object.
Gravity is a constant. Pedaling forces are not even remotely constant. The instant pedaling force is reduced forget about momentum and forward inertia. Gravity takes over instantly. The bike must be accelerated again after every slightest lapse in pedaling perfection. Climbing is an exercise in continuous acceleration. Which is hard.
The most accurate and helpful part of this discussion is the observation that red bikes are faster.
Most riders can hold a reasonably steady power output. They might well have the odd surge or dip in speed, but I wouldn't say climbing is an exercise in "continuous acceleration". Not unless you want to make it harder than it needs to be.
Any half reasonable dynamic model (e.g. Best Bike Splits) can tell you how long it will take to climb up any known hill/mountain given your average power and other basic parameters I mentioned earlier. It's not that hard.
If one bike climbs better than another it's either because it weighs less, has less rolling resistance, less aero drag (not so critical, but still counts for something) or somehow allows the rider to output more power e.g. better position.