Bikes freewheel, or coast, using a special internal mechanism located in the rear wheel's gear assembly. This mechanism allows the rear wheel to continue spinning forward even when you stop pedaling or pedal backward.
The Freewheel Component
According to the reference, "A Freewheel is a single gear or cluster of Gears that contains an internal ratcheting mechanism that allows you to Coast." This component, which holds the gears, threads onto the rear hub shell of the bicycle wheel.
The Internal Ratcheting Mechanism
The core of the freewheeling ability lies within this ratcheting mechanism. It's a clever system of spring-loaded pawls (small levers or teeth) and a notched ring (the ratchet).
Here's a simple breakdown of how it works:
- When you pedal forward: The pawls are pushed by the driver mechanism inside the freewheel and engage with the notches on the ratchet ring. This engagement locks the gear cluster to the rear wheel hub, transferring power from the pedals to the wheel and propelling the bike forward.
- When you stop pedaling or pedal backward: The pressure from the driver mechanism is removed. The spring-loaded pawls can then slide over the notches in the ratchet ring. This disengagement allows the wheel to spin freely while the gears and pedals remain stationary or move backward. This is the coasting action.
The familiar clicking sound you hear when freewheeling is the sound of the pawls sliding over the ratchet notches.
Location and Function
This freewheel unit is specifically located on the rear hub of the bicycle. Its primary function is to enable you to rest your legs while the bike is in motion, improving efficiency and rider comfort, especially on downhill sections or flat terrain where maintaining speed doesn't require continuous pedaling. It's an essential part of most multi-speed and many single-speed bicycles, allowing for safe and effective coasting.
