How does a bicycle work?

Two triangles, a chain and a wheel of thin wires, and a machine that balances itself. Most bikes use a diamond frame: two triangles sharing the seat tube. A triangle can't change shape unless one side changes length, so thin, light tubes make a stiff frame.

Read how it works: How does a bicycle work? · The history of the bicycle · More boxes on Glassbox

Chapters in this interactive model

1. Anatomy of a bicycle: Two triangles, two wheels, a chain and a way to steer.
2. Pedal to wheel: chain and gears: A chain links two sprockets; their sizes set how far each pedal stroke takes you.
3. Gears on a hill: Why a bigger rear cog makes a climb feel easier.
4. Why a moving bike stays up: At speed, the front wheel steers into every fall and catches it.
5. A wheel of thin wires: Spokes can only pull, yet the wheel carries your weight.
6. Stopping: brakes make heat: Your speed has to go somewhere. Brakes turn it into heat.