When a bicycle rides on the road surface, let the gravity of the bicycle, people and loads be G, the friction coefficient of the road surface be μ, the traction force of people riding is F, and the slope is α.

Then on the flat road surface, when f > μ g, it can move forward;

On the slope, when F > μ g * cos α, you can climb the slope;

On a vertical cliff, when F is greater than G, it can be launched vertically.